Pediatric Neuroblastoma

Chromosomal and molecular markers

Over the last 2 decades, many chromosomal and molecular abnormalities have been identified in patients with neuroblastoma. These biologic markers have been evaluated to determine their value in assigning prognosis, and some of these have been incorporated into the strategies used for risk assignment.

The most important of these biologic markers is MYCN. MYCN is an oncogene that is overexpressed in approximately one quarter of cases of neuroblastoma via the amplification of the distal arm of chromosome 2. This gene is amplified in approximately 25% of de novo cases and is more common in patients with advanced-stage disease. Patients whose tumors have MYCN amplification tend to have rapid tumor progression and poor prognosis, even in the setting of other favorable factors such as low-stage disease or 4S disease.

In contrast to MYCN, expression of the H-ras oncogene correlates with lower stages of the disease. Cytogenetically, the presence of double-minute chromatin bodies and homogeneously staining regions correlates with MYCN gene amplification. Deletion of the short arm of chromosome 1 is the most common chromosomal abnormality present in neuroblastoma and confers a poor prognosis. The 1p chromosome region likely harbors tumor suppressor genes or genes that control neuroblast differentiation. Deletion of 1p is more common in near-diploid tumors and is associated with a more advanced stage of the disease. Most of the deletions of 1p are located in the 1p36 area of the chromosome.

A relationship between 1p loss of heterozygosity (LOH) and MYCN amplification has been described. Other allelic losses of chromosomes 11q, 14q, and 17q have been reported, suggesting that other tumor suppressor genes may be located in these chromosomes. Loss of heterozygosity at 11q23 has been described and is an independent prognostic factor. Another characteristic of neuroblastoma is the frequent gain of chromosome 1.

DNA index is another useful test that correlates with response to therapy in infants. Look et al. demonstrated that infants whose neuroblastoma have hyperdiploidy (ie, DNA index >1) have a good therapeutic response to cyclophosphamide and doxorubicin.[1] In contrast, infants whose tumors have a DNA index of 1 are less responsive to the latter combination and require more aggressive therapy. DNA index does not have any prognostic significance in older children. In fact, hyperdiploidy in children more frequently occurs in the context of other chromosomal and molecular abnormalities that confer a poor prognosis.

Three neurotrophin receptor gene products, TrkA, TrkB, and TrkC, are tyrosine kinases that code for a receptor of members of the nerve growth factor (NGF) family. Their ligands include p75 neurotrophin receptor (p75NTR) NGF, and brain-derived neurotrophic factors (BDNFs). Interestingly, TrkA expression is inversely correlated with the amplification of the MYCN gene, and the expression of the TrkC gene is correlated with TrkA expression. In most patients younger than 1 year, a high expression of TrkA correlates with a good prognosis, especially in patients with stages 1, 2, and 4S. In contrast, TrkB is more commonly expressed in tumors with MYCN amplification. This association may represent an autocrine survival pathway.

Disruption of normal apoptotic pathways may also play a role in neuroblastoma pathology. Disruption of these normal pathways may play a role in therapy response as a result of epigenetic silencing of gene promoters in apoptotic pathways. Drugs that target DNA methylation, such as decitabine, are being explored in preliminary studies.

Other biologic markers associated with poor prognosis include increased levels of telomerase RNA and lack of expression of glycoprotein CD44 on the tumor cell surface. P-glycoprotein (P-gp) and multidrug resistance protein (MRP) are 2 proteins expressed in neuroblastoma. These proteins confer a multidrug-resistant (MDR) phenotype in some cancers. Their role in neuroblastoma is controversial. Reversal of MDR is one target for novel drug development.

A study by Challagundla et al reported that exosomic microRNAs released within the neuroblastoma environment affect resistance to chemotherapy.[2]

Anatomic

Origin and migration pattern of neuroblasts during fetal development explains the multiple anatomic sites where these tumors occur; location of tumors varies with age. Tumors can develop in the abdominal cavity (40% adrenal, 25% paraspinal ganglia) or other sites (15% thoracic, 5% pelvic, 3% cervical tumors, 12% miscellaneous). Infants more commonly present with thoracic and cervical tumors, whereas older children more frequently have abdominal tumors.

Most patients present with signs and symptoms related to tumor growth, although small tumors have been detected due to the common use of prenatal ultrasonography. Large abdominal tumors often result in increased abdominal girth and other local symptoms (eg, pain). Paraspinal dumbbell tumors can extend into the spinal canal, impinge on the spinal cord, and cause neurologic dysfunction.

Stage of the tumor at the time of diagnosis and age of the patient are the most important prognostic factors. Although patients with localized tumors (regardless of age) have an excellent outcome (80-90% 3-year event-free survival [EFS] rate), patients older than 18 months with metastatic disease fare poorly. Generally, more than 50% of patients present with metastatic disease at the time of diagnosis, 20-25% have localized disease, 15% have regional extension, and approximately 7% present during infancy with disseminated disease limited to the skin, liver, and bone marrow (stage 4S).

Physiologic and biochemical

More than 90% of patients have elevated homovanillic acid (HVA) and/or vanillylmandelic acid (VMA) levels detectable in urine. Mass screening studies using urinary catecholamines in neonates and infants in Japan, Quebec, and Europe have demonstrated the ability to detect neuroblastoma before it is clinically apparent. However, most of the tumors identified occur in infants with a good prognosis. None of these studies shows that mass screening decreases deaths due to high-risk neuroblastoma.

Markers associated with a poor prognosis include (1) elevated ferritin levels, (2) elevated serum lactate dehydrogenase (LDH) levels, and (3) elevated serum neuron-specific enolase (NSE) levels. However, these markers have become less important due to the discovery of more relevant biomarkers (ie, chromosomal and molecular markers). In fact, ferritin was not included in the recent formulation of the International Neuroblastoma Risk Group Classification System because it was not found to be of prognostic difference in the high-risk group.

Histologic

Pluripotent sympathetic stem cells migrate and differentiate to form the different organs of the sympathetic nervous system. The normal adrenal gland consists of chromaffin cells, which produce and secrete catecholamines and neuropeptides. Other cells include sustentacular cells, which are similar to Schwann cells, and scattered ganglion cells. Histologically, neural crest tumors can be classified as neuroblastoma, ganglioneuroblastoma, and ganglioneuroma, depending on the degree of maturation and differentiation of the tumor.

The undifferentiated neuroblastomas histologically present as small, round, blue cell tumors with dense nests of cells in a fibrovascular matrix and Homer-Wright pseudorosettes. These pseudorosettes, which are observed in 15-50% of tumor samples, can be described as neuroblasts surrounding eosinophilic neuritic processes. The typical tumor shows small uniform cells with scant cytoplasm and hyperchromatic nuclei. A neuritic process, also called neuropil, is a pathognomonic feature of neuroblastoma cells. NSE, chromogranin, synaptophysin, and S-100 immunohistochemical stains are usually positive. Electron microscopy can be useful because ultrastructural features (eg, neurofilaments, neurotubules, synaptic vessels, dense core granules) are diagnostic for neuroblastoma.

In contrast, the completely benign ganglioneuroma is typically composed of mature ganglion cells, Schwann cells, and neuritic processes, whereas ganglioneuroblastomas include the whole spectrum of differentiation between pure ganglioneuromas and neuroblastomas. Because of the presence of different histologic components, the pathologist must thoroughly evaluate the tumor; the regions with different gross appearance may demonstrate a different histology.

Neuroblastic nodules are present in the fetal adrenal gland and peak at 17-18 weeks' gestation. Most of these nodules spontaneously regress and likely represent remnants of fetal development. Some of these may persist and lead to the development of neuroblastoma.

Shimada histopathologic classification system

Shimada et al developed a histopathologic classification in patients with neuroblastoma.[3] This classification system was retrospectively evaluated and correlated with outcome in 295 patients with neuroblastoma who were treated by the Children's Cancer Group (CCG). Important features of the classification include (1) the degree of neuroblast differentiation, (2) the presence or absence of Schwannian stromal development (stroma-rich, stroma-poor), (3) the index of cellular proliferation (known as mitosis-karyorrhexis index [MKI]), (4) nodular pattern, and (5) age. Using these components, patients can be classified into the following histology groups:

Favorable histology group includes the following:

• Patients of any age with stroma-rich tumors without a nodular pattern

• Patients younger than 18 months with stroma-poor tumors, an MKI of less than 200/5000 (200 karyorrhectic cells per 5000 cells scanned), and differentiated or undifferentiated neuroblasts

• Patients younger than 60 months with stroma-poor tumors, an MKI of less than 100/5000, and well-differentiated tumor cells

Unfavorable histology group includes the following:

• Patients of any age with stroma-rich tumors and a nodular pattern

• Patients of any age with stroma-poor tumors, undifferentiated or differentiated neuroblasts, and an MKI more than 200/5000

• Patients older than 18 months with stroma-poor tumors, undifferentiated neuroblasts, and an MKI more than 100/5000

• Patients older than 18 months with stroma-poor tumors, differentiated neuroblasts, and an MKI of 100-200/5000

• Patients older than 60 months stroma-poor, differentiated neuroblasts, and an MKI less than 100

Shimada et al’s original classification was adopted and integrated into the International Neuroblastoma Pathology Classification (INPC). This was most recently revised.[4] The INPC system remains age-dependent.

The cause of neuroblastoma is unknown, and no specific environmental exposure or risk factors have been identified.

Because of young age of onset with this disease, investigators have focused on events before conception and during gestation.

According to SEER data, factors investigated for which evidence is limited or inconsistent include medications, hormones, birth characteristics, congenital anomalies, previous spontaneous abortion or fetal death, alcohol or tobacco use, and paternal occupational exposures.

The vast majority of neuroblastoma arises sporadically without family history of the disease. However, 1-2% of newly diagnosed cases do have a family history of neuroblastoma. Patients with familial neuroblastoma often present at earlier age or with several distinct primary tumors.

Neuroblastoma has been known to occur in the setting of other disorders that are linked to abnormal development of neural crest tissues, such as Hirschsprung disease or central congenital hypoventilation syndrome. Genome-wide analysis of neuroblastoma from these rare familial cases has identified a genetic defect involved in these cases. Cases of neuroblastoma that accompany other congenital abnormalities of the neural crest have been associated with a germline mutation in PHOX2B. This gene is a homeobox gene that acts as a regulator of autonomic nervous system development.

In familial neuroblastoma cases that are not associated with other congenital disorders of neural crest development, ALK mutations have been identified in the germline.[5]  These mutations largely occur in the kinase domain causing activation of ALK signaling. Efforts are ongoing to investigate the incidence of ALK mutations across all subsets of neuroblastoma, but initial evidence indicates that somatic mutations of the ALK gene are also present in some cases of sporadic neuroblastoma.

A 2014 study reported that deep-sequencing techniques can identify new ALK mutations at relapse of neuroblastoma, suggesting that patients would benefit from repeated tumor sampling.[6]

De Brouwer et al illustrate the occurrence of the ALK mutation specifically in neuroblastomas. Although they studied a small proportion of cases, mutations were found in similar frequencies in favorable and unfavorable outcome cases. The F1174L mutant was found more frequently in the poor outcome subgroup.[7]  This example illustrates the heterogeneity of cancer and the likely possibility that targeted therapies to the ALK gene may be of benefit in a subset of ALK cancers, which may possibly include a small subset of MYC-amplified neuroblastomas. The challenge for drug development in neuroblastoma is to identify upfront high-risk cases that may benefit from ALK-directed therapy.

Genome-wide association studies (GWAS) have been used to discover numerous genetic variations associated with neuroblastoma. Variations in LMO1, BARD1, and FLJ22536 have all been associated with aggressive forms of neuroblastoma.[8, 9, 10]  Genomic variations within DUSP12, DDX4, IL21RA, and HSD17B12 are associated with low-risk forms of neuroblastoma.[11]

United States statistics

Neuroblastoma accounts for approximately 6% of childhood cancers in the United States.[12] About 650 new cases are diagnosed in the United States each year. According to the Surveillance, Epidemiology, and End Report (SEER), incidence is approximately 9.5 cases per million children.[13]

International statistics

The incidence in other industrialized nations appears to be similar to that observed in the United States. International reports have shown that the incidence rates of neuroblastoma are highest among high income countries in Europe and North America, and lower in low income countries in Africa, Asia, and Latin America. No published data are available on the incidence in the emerging high-income countries of Asia.[14]

Race-, sex-, and age-related demographics

The incidence of neuroblastoma is higher in White children than in Black children. However, race does not appear to have any effect on outcome.

Males have a slightly higher incidence of neuroblastoma than females, with a male-to-female ratio of 1.2:1.

Age distribution is as follows: 40% of patients are younger than 1 year when diagnosed, 35% are aged 1-2 years, and 25% are older than 2 years when diagnosed. According to SEER, incidence decreases every consecutive year up to age 10 years, after which the disease is rare.[13]

Determinants of response and outcome include the following:

• Stage, age, and several biologic characteristics of the tumor determine outcome.

• Similarly, the patient may also have genetic polymorphism characteristics that influence drug absorption, distribution, metabolism, and excretion.

The following treatment strategies are available to treat patients with recurrent neuroblastoma:

• A local recurrence in a patient with low-stage disease generally has a good prognosis, and patients usually receive standard chemotherapy, surgery, and/or radiation as necessary.

• Patients with disseminated disease at presentation have a high recurrence rate and a poor outcome.

• For patients with recurrent disease in this setting, various phase I/II agents are generally available.

The following response criteria are used to evaluate the efficacy of therapy:

• Complete clinical response - More than 90% decrease (sum of the products of the greatest perpendicular diameters) of the primary tumor and metastatic disease (if any), no new lesions, healing of bone lesions

• Partial clinical response - A decrease of 50% or less (sum of the products of the greatest perpendicular diameters) of the primary tumor and metastatic disease (if any), no new lesions, healing of bone lesions

• Minor response - More than 25% and less than 50% decrease (sum of the products of the greatest perpendicular diameters) of primary tumor and metastatic disease (if any), no new lesions, healing of bone lesions

• No response - Less than 25% decrease (sum of the products of the greatest perpendicular diameters) of primary tumor or metastatic disease (if any), no new lesions

• Progressive disease - More than 25% increase (sum of the products of the greatest perpendicular diameters) of the primary tumor or all metastatic lesions (if any), appearance of new lesions

Morbidity/mortality

According to the SEER data, the overall 5-year survival rate for children with neuroblastoma has improved from 24% in 1960-1963 to 55% in 1985-1994.[13]  In part, this increase in survival rate may be due to better detection of low-risk tumors in infants. The survival rate 5 years from diagnosis is approximately 83% for infants, 55% for children aged 1-5 years, and 40% for children older than 5 years. Improvements in diagnostic imaging modalities, medical and surgical management, and supportive care have contributed to the improved survival rates.[15]

Most patients with neuroblastoma present with disseminated disease, which confers a poor prognosis and is associated with a high mortality rate. Tumors in these patients usually have unfavorable pathologic and/or molecular features. The 3-year EFS for high-risk patients treated with conventional chemotherapy, radiation therapy, and surgery is less than 20%. Differentiating agents and dose intensification of active drugs, followed by autologous bone marrow transplant, have been reported to improve the outcome for these patients, contributing to an EFS of 38%. A recent single-arm study of tandem stem cell transplantation reported a 3-year EFS of 58%, but randomized studies of this approach are ongoing.[16]

Morbidity of high-dose chemotherapy approaches can be substantial, although the treatment-related mortality rates have decreased with improvements in supportive care and hematopoietic support with growth factors and stem cells instead of bone marrow.

Complications

The following complications may occur:

• The most worrisome complication at disease presentation is cord compression from a paraspinal tumor. Evaluation of the patient by a neurosurgeon and consultation with a radiation oncologist are important.

• In some individuals with neuroblastomas, early institution of chemotherapy is accepted if the tumor can be biopsied within 72 hours to make a diagnosis and to obtain necessary biologic studies. In the acute setting, chemotherapy may be as efficient as radiotherapy or laminectomy, and it may cause less morbidity. Treatment of cord compression with chemotherapy and steroids usually results in less complications; however, radiation therapy or surgery is often used as front-line treatment to prevent impending or progressive neurologic damage. In children who present with significant neurologic symptoms, none of these interventions assure a return of normal neurologic (motor) function.

• Tumor lysis syndrome is unusual in neuroblastoma

• Patients may present with severe hypertension or renal insufficiency, making initiation of chemotherapy, especially with platinum drugs, more difficult.

• Myelosuppression and immunosuppression place the patient at risk of bleeding and infection. Febrile neutropenia is a medical emergency and requires immediate admission to the hospital and initiation of broad-spectrum antibiotic treatment.

• After several cycles of therapy, depending on drugs administered, patients may develop impaired renal function, hearing loss, or delayed count recovery.

For compliance and good medical care, patients and families must understand the importance of treatment and adverse effects of medications used. In addition, they should learn to recognize and identify signs and symptoms of complications that require urgent medical care.

For further information for patients and their families, see the WebMD Medical Reference article What Is Neuroblastoma?

The following may be noted in patients with neuroblastoma:

• Signs and symptoms of neuroblastoma vary with site of presentation. Generally, symptoms include abdominal pain, emesis, weight loss, anorexia, fatigue, and bone pain. Hypertension is an uncommon sign of the disease and is generally caused by renal artery compression, not catecholamine excess. Chronic diarrhea is a rare presenting symptom secondary to tumor secretion of vasoactive intestinal peptide secretion.

• Because more than 50% of patients present with advanced stage disease, usually to the bone and bone marrow, the most common presentation includes bone pain and a limp. However, patients may also present with unexplained fever, weight loss, irritability, and periorbital ecchymosis secondary to metastatic disease to the orbits. The presence of bone metastases can lead to pathologic fractures.

• Approximately two thirds of patients with neuroblastoma have abdominal primaries. In these circumstances, patients can present with an asymptomatic abdominal mass that usually is discovered by the parents or a caregiver. Symptoms produced by the presence of the mass depend on its proximity to vital structures and usually progress over time.

• Tumors that arise from the paraspinal sympathetic ganglia can grow through the spinal foramina into the spinal canal and impinge on the spinal cord. This may result in the presence of neurologic symptoms, including weakness, limping, paralysis, and even bladder and bowel dysfunction.

• Thoracic neuroblastomas (posterior mediastinum) may be asymptomatic and are usually diagnosed by imaging studies obtained for other reasons. Presenting signs or symptoms may be insignificant and involve mild airway obstruction or chronic cough, leading to chest radiography.

• Thoracic tumors extending to the neck can produce Horner syndrome. Primary cervical neuroblastoma is rare but should be considered in the differential diagnosis of masses of the neck, especially in infants younger than 1 year with feeding or respiratory difficulties.

• In a small proportion of infants younger than 6 months, neuroblastoma presents with a small primary tumor and metastatic disease confined to the liver, skin, and bone marrow (stage 4S). If this type of tumor develops in neonates, skin lesions may be confused with congenital rubella, and, if the patient has severe skin involvement, the term "blueberry muffin baby" may be used.

• Approximately 2% of patients present with opsoclonus and myoclonus a paraneoplastic syndrome characterized by the presence of myoclonic jerking and random eye movements. These patients often have localized disease and a good long-term prognosis. Unfortunately, the neurologic abnormalities can persist or progress and can be devastating.

• Finally, intractable diarrhea is a rare paraneoplastic symptom and is associated with more differentiated tumors and a good prognosis.

The following may be noted in patients with neuroblastoma:

• Children are usually referred to a pediatric oncologist by primary care providers who have identified a persistent unexplained symptom or sign, either upon physical examination or based on screening test findings.

• In patients with suspected neuroblastoma, performing a thorough examination with careful attention to vital signs (eg, blood pressure), neck, chest, abdomen, skin, and nervous system is essential.

• Metastatic lesions of the skin are common in infants younger than 6 months and may represent stage 4S disease.

• Examination of the abdomen may reveal an abdominal mass, leading to the appropriate workup.

• Neurologic examination may reveal Horner syndrome. In the case of dumbbell tumors, compression of the spinal cord may produce lower extremity weakness or paraplegia. Patients with neurologic involvement by tumor should be treated emergently, secondary to the risk of permanent neurologic sequelae.

Any child with a presumed diagnosis of neuroblastoma or any other childhood cancer should be referred to a pediatric cancer center for proper care and evaluation. Laboratory studies should include the following:

• Complete blood cell (CBC) count and differential - Anemia or other cytopenias suggest bone marrow involvement

• Urine collection for catecholamines (VMA/HVA) and UA

  • A single sample or collected urine test for VMA/HVA is highly accurate in CLIA approved laboratories. Centers usually send samples to a specialty laboratory and/or perform a timed collection of urine.

  • A urinary catecholamine level is considered to be elevated if it is 3 standard deviations higher than the age-related reference range levels.

• Serum creatinine

• Liver function tests

  • Alanine aminotransferase (ALT)

  • Aspartate aminotransferase (AST)

  • Total bilirubin

  • Alkaline phosphatase

  • Total protein

  • Albumin

  • Prothrombin time (PT)/activated prothrombin time (aPTT)

• Electrolytes

• Calcium

• Magnesium

• Phosphorus

• Uric acid

• Serum lactate dehydrogenase (LDH)

• Ferritin

• Thyroid-stimulating hormone (TSH), T4

• Immunoglobulin (Ig)G levels

The following studies may be indicated in patients with neuroblastomas:

• Obtain chest and abdominal radiographs to evaluate for the presence of a posterior mediastinal mass or calcifications.

• A CT scan of the primary site is essential to determine tumor extent. The main body of the tumor is usually indistinguishable from nodal masses. See the images below.

  CT scan of abdomen in a patient with a retroperitoneal mass arising from the upper pole of the left kidney and elevated urine catecholamines.

  A one-week-old neonate had abdominal ultrasonography for evaluation of projectile vomiting. A right adrenal mass (100% cystic) was an incidental finding. Evaluation of the mass by CT was consistent with an adrenal bleed (3.6 x 3.1 x 2.4 cc). The infant was followed at 2 weeks (2-dimensional size diminished to 1.5 x. 2.4 cm2 on ultrasonography) and then at 6 weeks to document that the adrenal bleed continued to involute. Urine catecholamines were normal.

• In cases of paraspinal masses, MRI aids in determining the presence of intraspinal tumor and cord compression. Horner syndrome should be evaluated with an MRI of the neck and head. See the image below.

  MRI of a left adrenal mass. The mass was revealed by fetal ultrasonography at 30 weeks' gestation. During infancy, the mass was found on the inferior pole of the left adrenal and was completely resected. Before surgery, the metastatic workup was negative. Surgical pathology service confirmed a diagnosis of neuroblastoma. After 3 years of follow-up care, no recurrence was observed.

• I123/131 -methyliodobenzylguanadine (MIBG) accumulates in catecholaminergic cells and provides a specific way of identifying primary and metastatic disease if present. Increasing numbers of institutions have access to MIBG scanning.

• A technetium-99 bone scan can also be used to evaluate bone metastases. This may be especially helpful in patients with negative MIBG study findings. Most current therapeutic protocols require both a bone scan and MIBG scan.

• Skeletal surveys may also be useful, especially in patients with multiple metastatic lesions.

• Positron emission tomography (PET) scan are under evaluation but are not currently recommended as part of the radiographic workup.

Obtain the following as baseline studies before therapy with anthracyclines:

• ECG

• Echocardiogram or resting radionuclide ejection fraction scan

Baseline hearing tests are recommended before cisplatin therapy. Baseline creatinine clearance should be measured (see the Creatinine Clearance (measured) calculator), especially if serum creatinine is abnormal.

Bilateral bone marrow aspirates and biopsies should be performed to exclude metastatic disease.

Biopsy or resection of the primary tumor (stage I or II disease) is performed to collect tissue samples for biologic studies used to assign the patient into the appropriate risk category. Most centers in the United States perform limited open biopsies when the primary tumor is unresectable upfront. Adequate tissue is needed to perform molecular studies that aid in risk assignment. Extensive resections should be avoided upfront if they may place patient at excessive risk from morbidity or mortality from surgery. Neuroblastoma is a chemo-sensitive tumor; thus, second-look surgery to resect a residual primary may be a safer procedure with biopsy only performed upfront.

Tissue samples from a primary or metastatic tumor may be undifferentiated and confused with other small, round, blue cell tumors of childhood; however, immunohistochemical stains can aid with tissue diagnosis.

Molecular techniques, such as fluorescent in situ hybridization (FISH), can detect MYCN amplification, an important prognostic marker. Polymerase chain reaction (PCR) can identify specific translocations, such as t(11;22), in Ewing sarcoma and t(2;13) in alveolar rhabdomyosarcoma, thus ruling out neuroblastoma.

Neuroblastoma in bone marrow can be difficult to distinguish from other small, round, blue cell tumors of childhood.

Biopsy findings are usually required to diagnose neuroblastoma. Depending on the extent of disease at presentation, consider complete surgical resection, especially in patients with low-stage disease. Even without a biopsy, the presence of elevated urinary catecholamines and a bone marrow aspirate or biopsy with unequivocal neuroblastoma cells is diagnostic.

Histologically, neural crest tumors can be classified as neuroblastoma, ganglioneuroblastoma, and ganglioneuroma, depending on the degree of maturation and differentiation of the tumor. Undifferentiated neuroblastomas histologically present as small, round, blue cell tumors with dense nests of cells in a fibrovascular matrix and Homer-Wright pseudorosettes. These pseudorosettes, observed in 15-50% of tumor samples can be described as neuroblasts surrounding eosinophilic neuritic processes. The typical tumor shows small uniform cells with scant cytoplasm and hyperchromatic nuclei. A neuritic process, also called neuropil, is a pathognomonic feature of neuroblastoma.

Histologic subtypes of neuroblastoma are shown in the image below.

Neuron-specific enolase (NSE), chromogranin, synaptophysin, and S-100 immunohistochemical stain findings are usually positive. Electron microscopy can be useful because ultrastructural features (eg, neurofilaments, neurotubules, synaptic vessels, dense core granules) are diagnostic for neuroblastoma. In contrast, the completely benign ganglioneuroma is typically composed of mature ganglion cells, Schwann cells, and neuritic processes, whereas ganglioneuroblastomas include the whole spectrum of differentiation between pure ganglioneuromas and neuroblastomas.

The pathologist must thoroughly evaluate the tumor because regions with different gross appearance may exhibit a different histology.

The patient should undergo a staging workup along with surgical resection or biopsy, as appropriate. Using various molecular features in conjunction with pathology and staging is essential to appropriately stratify patients and determine the best therapy.

The International Neuroblastoma Staging System (INSS) is currently used in all cooperative group studies in the United States. Recently, the International Neuroblastoma Risk Group Staging System (INRGSS) and International Neuroblastoma Risk Group Consensus Pretreatment Classification were released.[17] The current INSS system is based on degree of surgical resection and thus is not appropriate for use with the INRG Pretreatment Classification. This is especially important because not all groups use upfront surgical resection as part of their staging system. The INRG was formulated to be used in international settings and to facilitate comparison of treatment outcomes across studies to allow common definitions among all groups. Thus, development of the INRGSS was facilitated using pretreatment tumor imaging rather than extent of surgical resection.

The INRGSS is as follows:

• L1 - Localized tumor not involving vital structures, as defined by the list of image-defined risk factors and confined to one body component

• L2 - Locoregional tumor with presence of one or more image-defined risk factors

• M - Distant metastatic disease

• MS - Metastatic disease in children younger than 18 months with metastases confined to skin, liver, and/or bone marrow

The INSS is as follows:

• Stage 1

  • Localized tumor with complete gross excision, microscopic residual disease, or both

  • Ipsilateral lymph nodes negative for tumor (Nodes attached to the primary tumor may be positive for tumor).

• Stage 2A

  • Localized tumor with incomplete gross resection

  • Representative ipsilateral nonadherent lymph nodes microscopically negative for tumor

• Stage 2B

  • Localized tumor, complete gross excision, or both with ipsilateral nonadherent lymph nodes positive for tumor

  • Enlarged contralateral lymph nodes, which are negative for tumor microscopically

• Stage 3

  • Unresectable unilateral tumor infiltrating across the midline, regional lymph node involvement, or both

  • Alternatively, localized unilateral tumor with contralateral regional lymph node involvement

• Stage 4 - Any primary tumor with dissemination to distant lymph nodes, bone, bone marrow, liver, skin, and/or other organs (except as defined for stage 4S)

• Stage 4S

  • Localized primary tumor (as defined for stages 1, 2A, or 2B) with dissemination limited to skin, liver, and/or bone marrow (< 10% involvement)

  • Limited to infants

Care of children with neuroblastoma is provided by a multidisciplinary team involving pediatric oncology, radiation oncologists, surgeons, and anesthesiologists, as well as nurse practitioners, nurses, pharmacists, psychologists, and physical and occupational therapists dedicated to the special needs of these children.

The table below outlines criteria for risk assignment based on the International Neuroblastoma Staging System (INSS), age, and biologic risk factors. This, in turn, determines the intensity of the therapy. These treatment strategies have been developed from more than 2 decades of experience with clinical trials in Children's Cancer Group (CCG) and Pediatric Oncology Group (POG), now known as the Children's Oncology Group (COG). Correlative biologic studies were pivotal in identifying biologic risk factors important for outcome. Currently, efforts are ongoing to develop an International Neuroblastoma Risk Group (INRG).

In addition, recently published results on correlative biologic studies and clinical outcome have lead to changes in an age cut-off of more than 365 days (365-547 d) for some patients with tumors in stages 3 and 4.[18, 19] These criteria are based on the analysis of several thousands of patients treated in cooperative group protocols in Australia, Canada, Europe, Japan, and the United States.[20]

Table 1. Current COG Neuroblastoma Risk Stratification (Open Table in a new window)

 

Low-risk group treatment strategy

Patients with localized respectable neuroblastoma (stage 1) have excellent event-free survival (EFS) rates with surgical excision of tumor only. Adjuvant chemotherapy is generally not needed for this group of patients. Even the presence of residual microscopic disease does not significantly affect the EFS. If patients develop recurrent disease, chemotherapy can be used, and the overall survival rate remains higher than 95%.

Similar therapy is offered to patients with stage 2A/2B disease who are presently assigned to a low-risk category if they have MYCN -non amplified tumors, regardless of age histology or ploidy. Patients with stage 2A/2B disease with amplified MYCN are considered high risk regardless of age and histology.

A study by the Pediatric Oncology Group of experience with conservative treatment of low-risk patients confirmed the excellent outcomes for these patients with surgery alone. However, overall survival seemed lower among patients with stage 2b, MYC-N nonamplified, unfavorable histology or diploid tumors; thus, in the future, this specific group of patients may require reconsideration of their risk categorization.[21]

Most patients with 4S disease (ie, non-MYCN –amplified tumors, favorable histology, hyperdiploid tumors in infants younger than 1 y) are also considered to be in the low-risk group and most experience spontaneous regression. Thus, observation or surgery alone is often all that is needed to manage these tumors. Chemotherapy may be used to control life-threatening situations such as respiratory distress or mechanical obstruction.

Intermediate-risk group treatment strategy

Surgery and multiagent chemotherapy comprise the backbone of therapy for intermediate risk group patients. Current efforts are ongoing to help understand which of this diverse group of patients can have therapy reduced without threatening the excellent EFS for these patients.

Intermediate-risk patients include children younger than 18 months with stage 3 and 4 disease and favorable biology (non-MYCN –amplified tumors, regardless of histology and DNA index). These patients are offered therapy with 4 of the most active drugs against neuroblastoma (ie, cyclophosphamide, doxorubicin, carboplatin, etoposide) for either 4 cycles, 6 cycles, or 8 cycles, depending on histology and DNA index and response to treatment. In these patients, surgery can be performed either at time of diagnosis or following multiagent chemotherapy. If residual disease is present after chemotherapy and surgery, radiation therapy could be considered. However, the use of radiation is controversial, although a POG study suggested that it improves outcome when administered to areas of residual disease postchemotherapy.

Baker et al conducted a prospective, phase 3, nonrandomized trial of 479 patients (270 patients with stage 3 disease, 178 patients with stage 4 disease, and 31 patients with stage 4S disease) to determine whether a 3-year estimated overall survival of more than 90% could be maintained with reduced duration of chemotherapy and reduced drug doses.[22] The resulting 3-year estimate of overall for the entire group was 96%±1%. The study concluded that among patients with intermediate-risk neuroblastoma, substantially reduced duration of chemotherapy and reduced doses of chemotherapeutic agents still resulted in excellent outcomes.

High-risk group treatment strategy

This group of patients seem to require treatment with multiagent chemotherapy, surgery, and radiotherapy, followed by consolidation with high-dose chemotherapy and peripheral blood stem cell rescue.

Current therapeutic protocols involve 4 phases of therapy, including induction, local control, consolidation and treatment of minimal residual disease. The 3-year EFS for patients in the high-risk group who are treated without such high-intensity therapy is less than 20%, compared with an EFS of 38% in patients treated with a single bone marrow transplant and cis-retinoic acid after transplant.

Induction therapy currently involves multiagent chemotherapy with non–cross-resistant profiles, including alkylating agents, platinum, and anthracyclines and topoisomerase II inhibitors. Current studies are ongoing to look at addition of topoisomerase I inhibitors as part of an upfront therapy during induction. Topotecan does display activity against relapsed neuroblastoma.

Local control involves surgical resection of primary tumor site as well as radiation to primary tumor site. Primary tumors are often more amenable to surgical resection after receiving upfront induction chemotherapy. Neuroblastoma is a very radiosensitive tumor, and chemotherapy plays an important role in control of disease in the high-risk setting.

Myeloablative consolidation therapy has shown to improve EFS for patients with high-risk neuroblastoma. Current data from trials in the United States and Europe support improved outcomes for patients receiving myeloablative consolidation therapy with etoposide, carboplatin, and melphalan. Recently, a single-arm study of tandem stem cell transplantation reported an EFS of 58%. A randomized study of tandem stem cell transplant against a single transplant is currently ongoing in the Children’s Oncology Group.[16] Because of significant improvements in time to recovery and a lower risk of tumor cell contamination, most centers now recommend the use of peripheral blood stem cell support over bone marrow for consolidation therapy.

Control of minimal residual disease with biologic agents has also been shown to improve survival. The most experience is with 13-cis -retinoic acid in a maintenance phase of therapy. This agent has been shown to cause differentiation in neuroblastoma cell lines. CCG-3891 showed a significant survival advantage with 3-year EFS of 38% for those patients receiving maintenance therapy with 13-cis -RA compared with 18% for those who did not receive this therapy. Recent data have showed improved survival in patients receiving 13-cis -RA in combination with immunomodulatory therapy with interleukin (IL)-2, granulocyte macrophage colony-stimulating factor (GM-CSF), and the chimeric anti-GD2 (gangliosidase) antibody when compared with 13-cis -RA alone.

On March 10, 2015, the US Food and Drug Administration (FDA) approved dinutuximab, which is a monoclonal antibody against GD2, for use in the treatment of high-risk neuroblastoma. It was approved as part of a multimodality regimen, including surgery, chemotherapy, and radiation therapy, for patients who have achieved at least a partial response to prior first-line multiagent. It is indicated in combination with granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-2 (IL-2) and 13-cis-retinoic acid (RA) for pediatric patients with high-risk neuroblastoma.

Danyelza (naxitamab), a humanized anti-GD2 monoclonal antibody, in combination with GM-CSF, was granted accelerated approval by the FDA for relapsed or refractory high-risk neuroblastoma in the bone or bone marrow demonstrating a partial response, minor response, or stable disease to prior therapy in patients 1 year or older. Approval was based on two single-arm open-label studies, Study 201 and Study 12-230. In Study 201, the overall response rate (ORR) was 45% (95% CI: 24%, 68%), and the duration of response (DOR) ≥6 months was 30%. In Study 12-230, the ORR was 34% (95% CI: 20%, 51%), with 23% of patients having a DOR of ≥6 months. For both trials, responses were observed in either the bone, bone marrow, or both.[23]

Future directions and experimental therapies

Other experimental therapies are currently under investigation for recurrent high-risk neuroblastoma, including aurora kinase inhibitors, antiangiogenic agents, histone deacetylase inhibitors, and therapeutic metaiodobenzylguanidine (MIBG).[24, 25]

A pilot trial that investigated a fixed dose of a unique anti-GD2 mAb, hu14.18K322A, combined with chemotherapy, cytokines, and haploidentical natural killer cells for 13 children with recurrent/refractory neuroblastoma reported a response rate of 61.5% (4 complete responses, 1 very good partial response, 3 partial responses and five had stable disease). One patient developed an unacceptable toxicity (grade 4 thrombocytopenia >35 days) and four patients discontinued treatment for adverse events.[26]

Surgical resection plays an important role in the treatment of patients with neuroblastoma. For patients with localized disease, surgical resection is curative. For patients with regional or metastatic disease, surgery to establish a diagnosis and obtain adequate samples for biologic studies is essential. Typically, second-look surgery postchemotherapy is used to attempt a complete resection. The emphasis in the second-look procedure is as complete a debulking as possible without sacrificing major organ function. Patients with residual disease postchemotherapy and surgery may benefit from the use of radiotherapy.

Neuroblastoma can be confused with other neoplastic or nonneoplastic diseases of childhood. The diagnosis can be challenging in the 10% of patients who present with normal urinary catecholamines.

Radiation oncologists may participate in the care of patients with neuroblastoma. Typically, they are consulted to evaluate patients whenever radiation therapy is a consideration. Usually, radiotherapy is localized to areas of residual microscopic disease, persistent disease, or both after chemotherapy and surgery.

In high-risk patients, the need for stem cell harvest and transplantation should be anticipated. These services should be included early in the planning phase of treatment.

Diet

Nutrition plays an important role in therapy. Children need adequate caloric intake to attain normal growth and development, and to recover from the adverse effects of therapy. Nutritionists typically help to provide adequate supportive care during therapy. Supplemental nutrition is often required during therapy. This should occur via the enteral route (nasogastric or gastric tube). The parenteral route should be used only after failure to supplement adequately using enteral feedings.

Activity

No specific restrictions are placed on activity. Patients who are thrombocytopenic should avoid strenuous activity and contact sports. Patients should avoid ill contacts, especially if neutropenic.

All chemotherapy orders are written by pediatric oncologists and countersigned, usually by another physician. With recurrent disease, various salvage protocols may be used; with refractory disease, a limited number of phase I/II studies are available through the Children's Oncology Group (COG) and New Approaches to Neuroblastoma Therapy (NANT) consortia.

Resources presented in this section should serve as a guide to indication, usual dosages, and adverse effects of specific agents. Antineoplastic drugs have a narrow therapeutic index and effective doses usually cause severe toxicities, some of which can be life threatening.

Individual chemotherapy drugs are discussed below. These agents are almost invariably given in combination. Commonly used combinations include the following:

• Vincristine, cyclophosphamide, and doxorubicin

• Carboplatin and etoposide

• Cisplatin and etoposide

• Ifosfamide and etoposide

• Cyclophosphamide and topotecan

Consolidation regimens used in neuroblastoma include the following:

• Carboplatin and etoposide with melphalan or cyclophosphamide

• Thiotepa and cyclophosphamide

• Melphalan and total body irradiation

In Europe, several studies have used busulfan with melphalan or cyclophosphamide. One commonly used salvage or relapse therapy regimen is the combination of topotecan and cyclophosphamide. The use or retinoids have been incorporated in maintenance regimens in the posttransplant setting. Irinotecan is also under investigation.

Class Summary

Cancer chemotherapy is based on an understanding of tumor cell growth and how drugs affect this growth. After cells divide, they enter a period of growth (ie, phase G1), followed by DNA synthesis (ie, phase S). The next phase is a premitotic phase (ie, G2), which is followed by a mitotic cell division (ie, phase M).

Cell division rate varies for different tumors. Most common cancers increase very slowly in size compared with normal tissues, and the rate may decrease further in large tumors. This difference allows normal cells to recover more quickly from chemotherapy than malignant cells; it is the rationale behind current cyclic dosage schedules.

Antineoplastic agents interfere with cell reproduction. Some agents are cell cycle specific, whereas others (eg, alkylating agents, anthracyclines, cisplatin) are not phase specific. Cellular apoptosis (ie, programmed cell death) is also a potential mechanism of many antineoplastic agents.

Carboplatin (Paraplatin)

Alkylating agent. Interferes with metabolism of DNA by covalent binding.

Cisplatin (Platinol)

Mechanism of action is similar to other alkylating agents. Binds and cross-links DNA strands.

Cyclophosphamide (Cytoxan)

Immunosuppressant antineoplastic agent. Metabolism of cyclophosphamide by hepatic microsomal enzymes produces active alkylating metabolites, which probably damage DNA.

Doxorubicin (Adriamycin)

Causes DNA strand breakage mediated by effects on topoisomerase II. Intercalates into DNA and inhibits DNA polymerase.

Etoposide (VP-16, VePesid)

Interacts with topoisomerase II and produces single strand breaks in DNA. Arrests cells in late S or G2 phase.

Ifosfamide (Ifex)

Alkylating agent. Metabolic activation by microsomal liver enzymes produces biologically active intermediates that attack nucleophilic sites, particularly on DNA.

Melphalan (Alkeran)

Inhibits mitosis by cross-linking DNA strands.

Isotretinoin (13-cis-retinoic acid, Accutane)

Vitamin A derivative. Interacts with retinoic acid responsive elements on DNA, which results in gene activation and differentiation of target cells.

Thiotepa (Thioplex)

Ethyleneimine derivative alkylating agent. Action involves transfer of the alkyl group to amino, carboxyl, hydroxyl, imidazole, phosphate, and sulfhydryl groups within the cell, altering structure and function of DNA, RNA, and proteins.

Vincristine (Oncovin)

Mitotic inhibitor. This vinca alkaloid binds tubulin leading to its depolymerization, resulting in mitotic inhibition and metaphase arrest.

Topotecan (Hycamtin)

Inhibits topoisomerase I, inhibiting DNA replication.

Class Summary

These agents act as a hematopoietic growth factor that stimulates the development of granulocytes. They are used to treat or prevent neutropenia when receiving myelosuppressive cancer chemotherapy and to reduce the period of neutropenia associated with bone marrow transplantation. They are also used to mobilize autologous peripheral blood progenitor cells for bone marrow transplantation and in the management of chronic neutropenia.

A multicenter, randomized trial by Ladenstein et al observed pediatric patients (n=239) with neuroblastoma in 16 countries.[27] Patients who were given primary prophylactic G-CSF had significantly fewer febrile neutropenic episodes, days with fever, hospital days, and antibiotic days compared with those who received symptom-triggered G-CSF. Other toxicities were significantly reduced as well including infections, fever, severe leukopenia, neutropenia, mucositis, nausea/vomiting, constipation, and weight loss.

Filgrastim (G-CSF, Neupogen)

Promotes growth and differentiation of myeloid progenitor cells. May improve survival and function of granulocytes. In the posttransplant setting, administer until marrow recovery with absolute neutrophil count >10,000.

Class Summary

Mesna is a prophylactic detoxifying agent used to inhibit hemorrhagic cystitis caused by ifosfamide and cyclophosphamide. In the kidney, mesna disulfide is reduced to free mesna. Free mesna has thiol groups that react with acrolein, which is the ifosfamide and cyclophosphamide metabolite considered to be responsible for urotoxicity.

Mesna (Mesnex)

Interacts in the bladder with acrolein, a toxic metabolite of cyclophosphamide or ifosfamide to prevent hemorrhagic cystitis.

Class Summary

Monoclonal antibodies that bind to the glycolipid disialoganglioside (GD2), expressed on neuroblastoma cells and on normal cells of neuroectodermal origin, have been shown to produce superior outcomes as part of a multimodality regimen.

Dinutuximab (Unituxin)

Dinutuximab is a chimetic monoclonal antibody that binds to the glycolipid disialoganglioside (GD2). GD2 is a glycolipid expressed on neuroblastoma cells and on normal cells of neuroectodermal origin, including central nervous system and peripheral nerves. Dinutuximab binds to cell surface GD2 and induces lysis of GD2-expressing cells through antibody-dependent cell-mediated cycotoxicity and complement-dependent cytotoxicity.

Naxitamab (Danyelza, Naxitamab-gqgk)

Humanized anti-GD2 monoclonal antibody stimulates the antibody-dependent cell-mediated cytotoxicity against GD-2 expressing tumor cells. It is indicated, in combination with GM-CSF, for adult and pediatric patients aged 1 year and older with relapsed or refractory high-risk neuroblastoma in the bone or bone marrow demonstrating a partial response, minor response, or stable disease to prior therapy.

The following are aspects of further outpatient care in patients with neuroblastoma:

• Patients are periodically monitored in the clinic after each course of therapy to monitor for complications and to assess response to therapy with diagnostic imaging. Myelosuppression and pancytopenia are common complications, and a CBC count with platelet count is obtained as often as twice per week. Some drugs (eg, cisplatin, carboplatin, ifosfamide) affect renal function; thus, close monitoring of electrolytes is required, with oral electrolyte supplementation when necessary. Blood product support is provided when the hemoglobin drops to less than 8 g/dL, the platelet count drops to less than 10,000, or any signs of bleeding are present.

• After completion of therapy, successfully treated patients require follow-up care and close surveillance for any signs or symptoms of recurrent disease. Follow-up care includes monitoring of urinary catecholamines, physical examination, and diagnostic imaging. Because most recurrences occur during the first 2 years following treatment, most protocols recommend close follow-up care during this interval.

• Patients who remain free of recurrent disease for 5 years are considered cured, although rare late relapses have been reported. Long-term follow-up care to assess impact of therapy on growth, development, and organ toxicity is essential.

The following are aspects of further inpatient care in patients with neuroblastoma:

• Children with neuroblastoma are admitted to the hospital to expedite the diagnostic workup when unstable or significantly symptomatic.

• In an asymptomatic child, workup can be performed in the outpatient setting.

• A central line is commonly placed when biopsy or resection is scheduled in intermediate- or high-risk patients.

• A pediatric oncologist and surgeons with expertise in managing childhood malignancies perform the initial evaluation.

• Other subspecialists, such as neurosurgeons or radiation oncologists, may participate in patient care, especially in cases of cord compression.

• Once the diagnosis is established and the staging workup is completed, the patient and family are instructed on the diagnosis and therapeutic options.

• Once the treatment plan is developed, chemotherapy is administered, usually in the inpatient setting.

• Following completion of the treatment cycle, patients are discharged home with detailed instructions for home care and with outpatient follow-up.

The following medications may be used:

• Infection prophylaxis: Chemotherapy agents cause myelosuppression and immunosuppression. All patients should receive prophylaxis against Pneumocystis jiroveci with trimethoprim/sulfamethoxazole (trimethoprim 2.5 mg/kg/dose twice daily), administered on 3 consecutive days per week. Prophylaxis is started before chemotherapy and continued for at least 3 months after completing therapy.

• Colony-stimulating factors: Granulocyte colony stimulating factor (G-CSF) support has become common in pediatric oncology as intensity of chemotherapy has increased. Treat with 5-10 mcg/kg/d subcutaneously to start 24-36 hours after the last dose of chemotherapy. G-CSF is continued until the absolute neutrophil count is 2,000-10,000. See the Absolute Neutrophil Count calculator.

  A mouse model study by Agarwal et al suggested that G-CSF promotes the growth of neuroblastoma cancer stem cells that may be responsible for cancer relapse.[28, 29]

Management by a primary care provider is as follows:

• With oncology team supervision, routine care can be carried out by the primary care provider for patient convenience.

• Monitoring of blood counts or chemistries and administration of blood products are common.

• Some primary care providers with experience in the treatment of febrile neutropenia may be able to manage this complication of chemotherapy. Patients may quickly destabilize upon initiation of antibiotic therapy; thus, access to critical care services is required.

• Maintain close contact with subspecialists and transfer the patient to the pediatric oncology center for any complications that may require specialized care.

The cause of neuroblastoma is unknown. No specific environmental exposure or risk factors have been identified.

Currently, no specific recommendations on how to prevent this disease are known.

Screening for neuroblastoma in an attempt to diagnose high-risk patients earlier in the course of their disease has uncovered many patients with low-risk disease but has not had an impact on outcome in high-risk disease.