Thyroid Cancer Guidelines

In recent years, the management of thyroid cancers has become far more nuanced. With specifically tailored treatments becoming commonplace, it is important to consider each patient individually. Additionally, it is important to note that while a number of different groups have put forth guidelines for the management of thyroid surveillance and cancer therapy, ^{[1, 2, 3, 4, 5, 6, 7]} there some controversy among guidelines regarding certain scenarios, which has  raised concerns about the effects on patient outcomes. ^[8] For the sake of clarity, this article will largely refer to guidelines from the following organizations, and the following classification systems:

• National Comprehensive Cancer Network (NCCN) ^[2]
• American Association of Clinical Endocrinology/Associazione Medici Endocrinologi (AACE/AME) Thyroid Nodule Task Force ^[4]
• American Thyroid Association (ATA) ^{[9, 10, 11, 12]}
• European Society for Medical Oncology (ESMO) ^[3]
• Bethesda System for Cytopathology ^[13]
• American College of Radiology (ACR) Thyroid Imaging, Reporting and Data System (TI-RADS) ^[14]

Evaluation of any thyroid complaint begins with a thorough history and a physical examination that includes inspection for adjacent cervical lymphadenopathy. Important historical factors are as follows:

• Age
• Sex
• Family history (ie, thyroid cancers, multiple endocrine neoplasia type 2a/b [MEN2a/b}, Cowden syndrome, Werner syndrome, familial adenomatous polyposis [FAP])
• Environmental exposures
• Radiation exposure

When a nodule is discovered, either incidentally on imaging or on physical exam, patients should undergo the following:

• Thyroid-stimulating hormone (TSH) screening
• Thyroid ultrasonography, including evaluation of cervical lymph nodes
• Radionuclide thyroid scanning may be considered in patients with low TSH or, in patients with multiple nodules, to determine the functional status of the nodules; hyperfunctional nodules are less commonly associated with malignancy ^[1]

The AACE/AME guideline has an algorithm that comprises data from clinical assessment, imaging, cytology, and molecular markers and incorporates both TI-RADS ^[14] and the Bethesda classification ^[13] to help guide clinical decisions regarding nodule evaluation and work-up. ^[15] Ultrasound (US) features are used to categorize risk of malignancy and classify nodules as low risk (US1), intermediate risk (US2), or high risk (US3). ^[15]

US1 criteria include the absence of any intermediate-risk or high-risk features and the presence of one or more of the following features:

• Spongiform composition (uniformly microcystic)
• Margins smooth, ill defined, or unable to be determined
• Oval or round shape
• Nodule cystic and anechoic
• Nodule solid or mixed and marked hyperechoic
• Nodule solid or mixed and hyperechoic
• Nodule solid or mixed and  isoechoic  and < 20 mm and lacking any US2/3 features

US2 criteria include the absence of any high-risk features and the presence of one or more of the following features:

• Echogenic foci that include intramodular macro-calcifications, peripheral rim calcifications, those difficult to characterize
• Irregular margin with protrusion into adjacent thyroid tissue
• Nodule solid or mixed and solid component is hypoechoic
• Nodule is solid or mixed and  isoechoic and  either > 20 mm or displaying ≥ 1 intermediate-risk feature and lacking any US3 features

US3 criteria include the presence of one or more of the following:

• Margin spiculated or with sharp angles
• Profoundly hypoechoic
• Microcalcifications
• Shape taller than wide

The AACE/AME guidelines use clinical criteria to guide consideration of fine needle aspiration (FNA). Features that argue against performing FNA are termed Clinical 1; those that favor FNA are termed Clinical 2. ^[15]

Presence of one or more of the following argues against performing FNA:

• Low thyrotropin level in a patient not taking thyroid hormone
• Autonomous nodule on imaging
• rior benign FNA of the same nodule
• Other medical conditions that take precedence
• History of prior lobectomy with vocal cord paralysis
• Significant comorbidity making thyroid surgery high risk
• Limited life expectancy (< 1 year)

Presence of one or more of the following favors performing FNA:

• History of head and neck radiation
• Compressive symptoms: dysphonia, dysphagia, or dyspnea without another cause
• Nodule position posterior or adjacent to thyroid capsule or trachea
• History of documented nodule growth
• History of progressive growth (ie, ≥50% increase in volume in ≤1 year, especially of the solid component, or 20% increase in 1 dimension)
• History of sudden enlargement
• Planned thyroid or parathyroid surgery
• Cosmetic concerns
• Patient preference or anxiety
• Protocol requiring documentation of cancer

The AACE/AME guidelines provide recommendations for follow-up of nodules, based on size and US risk classification. For nodules smaller than 5 mm, recommendations are as follows:

• US1/2 - No follow-up
• US3 - Follow-up at 18-24 months

For nodules 5-10 mm, recommendations are as follows:

• US1 - No follow-up
• US2/Clinical 1 - recommendations are as follows:
• US2/Clinical 2 or US3 - Consider FNA or 12-24 month follow-up

For nodules > 10-20 mm, recommendations are as follows:

• US1/Clinical 1 - Follow-up at 18-24 months
• US1/Clinical 2 - Follow-up at 12 months
• US2/Clinical 1 - Consider FNA
• US2/Clinical 2 - FNA
• US3 - FNA

For nodules > 20-40 mm, recommendations are as follows:

• US1 - Consider FNA
• US2/3 - FNA

For nodules > 40 mm, FNA is recommended.

FNA results are best evaluated based on the Bethesda classification. ^[13] Classifications, follow-up, and malignancy risk are as follows:

• I. Nondiagnostic/poor specimen: Repeat FNA with ultrasound guidance; 5-10% risk of malignancy
• II. Benign: Clinical and US follow-up; 0-3% risk of malignancy
• III. Atypia of undetermined significance (AUS) or follicular lesion of undetermined significance (FLUS): Repeat FNA, molecular testing or lobectomy; 6-18% risk of malignancy (10-30% with non-invasive follicular thyroid neoplasm with papillary-like nuclear features [NIFTP])
• IV. Follicular neoplasm or suspicious for follicular neoplasm: Molecular testing plus lobectomy; 10-40% risk of malignancy (25-40% with NIFTP)
• V. Suspicious for malignancy: Total thyroidectomy or lobectomy; 45-60% risk of malignancy (50-75% with NIFTP)
• VI. Malignant: Total thyroidectomy or lobectomy; 94-99% risk of malignancy

Of note, NIFTP was formerly referred to as encapsulated follicular variant papillary thyroid carcinoma (eFVPTC) without capsular or vascular invasion. ^[16]

NCCN guidelines provide treatment recommendations based on the Bethesda classification, as follows ^[2] :

• Bethesda III (AUS/FLUS): If high clinical/radiographic suspicion, thyroidectomy or lobectomy; if low suspicion, consider repeat FNA, molecular diagnostics, nodular surveillance, or diagnostic lobectomy (if Bethesda III on two or more occasions)
• Bethesda IV (confirmed or suspicious for follicular or Hürthle cell): If high clinical and/or radiographic suspicion of malignancy, thyroidectomy or lobectomy; if low suspicion, consider diagnostic lobectomy, molecular diagnostics, or surveillance if low risk per TI RADs ^[14] /patient preference
• Bethesda V or VI (carcinoma or suspicious for carcinoma): Follow treatment paradigm for respective subtype (papillary, medullary, anaplastic)

When molecular testing is performed on lesions, as per the NCCN guidelines (ie, high-suspicion Bethesda III or low-suspicion BethesdA IV), those lesions that lack informative molecular diagnostics or are suggestive of malignancy should be considered for lobectomy or thyroidectomy. If testing shows Bethesda V or VI, subtype-specific treatment is recommended. If molecular diagnostics are suggestive of malignancy, considerations include lobectomy or total thyroidectomy for definitive diagnosis and treatment, or nodule surveillance. ^[2]

Differentiated thyroid cancers arise from thyroid follicular epithelial cells and constitute 90% of all thyroid cancers. The subtypes and approximate frequencies of differentiated thyroid cancers are as follows:

• Papillary – 85%
• Follicular – 10%
• Hürthle or oxyphil – 5%

ATA guidelines state that fine needle aspiration biopsy (FNAB) provides the most economical and accurate methodology for diagnosing differentiated thyroid cancers. Due to potential false negatives or sampling error, it is recommended that FNAB procedures be performed under ultrasound (US) guidance, especially for nodules located posteriorly and for those that are difficult to palpate. Additionally, certain features found on US examination are predictive for malignancy and may guide FNAB decision-making.

Papillary thyroid cancer is characterized by the following US features:

• Solid or predominantly solid
• Hypoechoic
• Microcalcifications (highly specific)
• Infiltrative irregular margins (common)
• Increased nodular vascularity

Follicular thyroid cancer is characterized by the following US features:

• Isoechoic to hyperechoic
• Thick irregular halo

Benign US features are as follows:

• Purely cystic nodule
• Spongiform appearance (aggregation of multiple micro-cystic components > 50% volume)

Malignancy risk

Cytological analysis of FNAB specimens is used to estimate malignancy risk. The most appropriate cytological classification of malignancy risk is the Bethesda system for thyroid cytopathology, which comprises the following categories ^[13] :

• Nondiagnostic/unsatisfactory sample: 5-10%
• Benign: 0-3%
• Atypia of undetermined significance or follicular lesion of undetermined significance: 6-18% (10-30% with NIFTP)
• Follicular neoplasm or suspicious for follicular neoplasm: 10-40% (25-40% with NIFTP)
• Suspicious for malignancy: 45-60% (50-75% with NIFTP)
• Malignant: 94-99%

For cytology “diagnostic of” or “suspicious for” papillary thyroid cancer, surgery is recommended. If FNAB cytology is indeterminate, the use of molecular markers such as BRAF, RAS, RET/PTC, Pax8-PPARɣ, or galectin-3 may be considered to guide management. ^[1]

An iodine-123 (¹²³I) thyroid scan may be considered if the cytology report documents a follicular neoplasm, especially if serum TSH is in the low-normal range. No radionuclide scan is needed for a reading of “suspicious for papillary carcinoma” or “Hürthle cell neoplasm”, as either lobectomy or total thyroidectomy is recommended, depending on the nodule size and risk factors. ^[1]

The NCCN recommends that FNAB should be the primary test for differentiated thyroid cancer. If FNAB reveals papillary carcinoma, follicular neoplasm, follicular lesion of undetermined significance, or Hürthle cell neoplasm, further diagnostic procedures should be selected accordingly, as shown below. ^[2]

Papillary carcinoma ≥ 1 cm:

• Thyroid and neck ultrasound (including central and lateral compartments) if not previously done
• Computed tomography (CT)/magnetic resonance imaging (MRI) for fixed, bulky, or substernal lesions (iodinated contrast optimal for cervical imaging)
• Consider evaluation of vocal cord mobility
• FNA of suspicious lateral neck nodes

Papillary carcinoma < 1 cm:

• Thyroid and neck ultrasound (including central and lateral compartments) if not previously done
• If concerning lymph nodes are present, manage as lesions ≥ 1 cm; if there are no concerning lymph nodes, surveillance or lobectomy if high risk

Follicular neoplasm (Bethesda IV) and Hürthle cell (Bethesda IV):

• Thyroid and neck ultrasound (including central and lateral compartments) if not previously done
• CT/MRI for fixed, bulky, or substernal lesions (iodinated contrast optimal for cervical imaging)
• Consider evaluation of vocal cord mobility

Medullary thyroid carcinoma:

• Basal serum calcitonin
• Pheochromocytoma screening
• Serum calcium
• Screen for RET proto-oncogene mutations
• Thyroid and neck ultrasound (including central and lateral compartments) if not previously done
• Consider evaluation of vocal cord mobility
• Additional cross-sectional imaging may be considered and could include contrast-enchanced CT of neck/chest; MRI/3-phase CT of liver; and Ga‑68 DOTATATE positron emission tomography (PET)/CT, bone scan, and/or skeletal MRI

If a RET proto-oncogene is identified, conduct genetic testing to determine whether the patient has multiple endocrine neoplasia type 2B (MEN2B) or MEN2A/familial medullary thyroid carcinoma (FMTC). ^[2]

For both MEN2B and MEN2A, further workup is as follows:

• Basal serum calcitonin
• Carcinoembryonic antigen (CEA)
• Pheochromocytoma screening
• Thyroid and neck ultrasound (including central and lateral compartments) if not previously done
• Consider evaluation of vocal cord mobility
• Consider neck CT with contrast

In addition, patients with MEN2A should have serum calcium and parathyroid hormone (PTH) measured.

The familial medullary thyroid carcinoma (MTC) syndromes consist of multiple endocrine neoplasia (MEN) types 2A and 2B and familial MTC. They are inherited in an autosomal dominant fashion. Children inheriting any of these syndromes have a 100% risk of developing MTC. In MEN 2B, MTC usually develops around 10 years of age and has a high propensity for rapid growth and metastasis. In MEN 2A, MTC can appear in the first decade of life, and it almost always develops by the second decade. MTC in FMTC usually develops during adulthood.

Guidelines from the American Thyroid Association (ATA) ^[9] and NCCN ^[2] recommend prophylactic thyroidectomy for individuals that have a documented RET mutation and are at risk for aggressive MTC. Risk varies with the underlying RET mutation.

The original ATA guidelines, from 2009, ^[17] stratified risk level of RET carriers into four categories, A through D, based upon the increasing aggressiveness of the particular mutation. Due to some confusion and lack of uniformity with other staging guidelines, the revised ATA guidelines, published in 2015, ^[9] transition category D to “highest risk” (HST), transition category C to “high risk” (H), and combine categories B and A into “moderate risk”. The risk stratification, screening schedules, and prophylactic thyroidectomy schedules are described in the table below.

Table. American Thyroid Association Medullary Thyroid Cancer Risk Levels and Treatment Recommendations (Open Table in a new window)

CEA=carcinoembryonic antigen;  Ctn=calcitonin; MEN=multiple endocrine neoplasia; US=ultrasound

The treatment of choice for differentiated thyroid cancers is surgery, whenever possible, followed by radioiodine (¹³¹I) in selected patients and thyrotropin suppression in most patients, according to the NCCN guidelines. ^[2] When suppression therapy is used, NCCN and ATA guidelines recommend basing the degree of suppression on the risk of recurrence, as follows ^{[1, 9]} :

• Low risk: Maintain TSH at or slightly below the lower limit of normal (0.1 to 0.5 mU/L)
• Intermediate risk: Initial TSH suppression to below 0.1 mU/L
• High risk: Initial TSH suppression to below 0.1 mU/L

The NCCN recommends that in patients who remain disease free for several years, TSH levels can probably be maintained within the reference range (0.5–2 mU/L). ^[2]

Papillary thyroid carcinoma (PTC)

NCCN guidelines recommend total thyroidectomy plus therapeutic neck dissection of any involved compartments for patients with PTC if any of the following are present ^[2] :

• Known distant metastases
• Extrathyroidal extension
• Tumor > 4 cm
• Lateral cervical or central neck lymph node metastases
• Poorly differentiated tumor
• Prior radiation exposure and bilateral nodularity

If none of those risk factors are present, total thyroidectomy versus lobectomy plus isthmusectomy can be considered.

NCCN recommendations for postoperative management include the following ^[2]

• If post-lobectomy pathology demonstrates any of the above high-risk characteristics, lymphatic invasion, or macroscopic multifocal disease (> 1 cm), the patient should undergo completion thyroidectomy.
• Consider levothyroxine treatment to maintain normal or low TSH and measuring thyroglobulin (TG) and anti-TG antibodies 6-12 weeks postoperatively. In patients with gross residual disease, TSH suppression therapy should be delayed until completion of radioactive iodine (RAI) work-up and treatment if indicated.
• For gross residual disease, patients can have TSH, TG, and anti-TG antibodies measured at 6-12 weeks or undergo ¹²³I or ¹³¹I total body imaging with TSH stimulation. The latter is preferred for viscerally invasive or rapidly progressing disease.

If RAI imaging shows no uptake, the NCCN recommends monitoring disease versus external beam or intensity-modulated radiation therapy (EBRT/IMRT). EBRT/IMRT can be considered upfront for patients with viscerally invasive disease or rapid progression. If RAI uptake is present, RAI treatment is preferred, followed by post-treatment ¹³¹I whole body imaging.

In patients with recurrent disease and widely metastatic disease, the tumor should be evaluated for actionable mutations such as ALK, NTRK, RET gene fusions, DNA mismatch repair (dMMR), micro-satellite instability (MSI), and tumor mutational burden (TMB). If found, they can be addressed with targeted therapies. ^[2]

Follicular thyroid cancer and Hürthle cell carcinoma

NCCN guidelines recommend total thyroidectomy for follicular thyroid cancer and Hürthle cell carcinoma that is invasive or metastatic, or if that is the patient's preference. Neck dissection is recommended for involved compartments. Otherwise, lobectomy/isthmusectomy can be performed; however, if pathology reports widely invasive cancer or encapsulated angioinvasive disease involving ≥4 vessels, completion thyroidectomy is indicated. ^[2]

Consideration should be given to levothyroxine treatment to maintain normal or low TSH and to measuring TG and anti-TG antibodies 6-12 weeks postoperatively. In patients with gross residual disease, TSH suppression therapy should be delayed until completion of RAI work-up and treatment if indicated.

For gross residual disease, patients can undergo measurement of TSH, TG, and anti-TG antibodies at 6-12 weeks or undergo ¹²³I or ¹³¹I total body imaging with TSH stimulation. The latter is preferred for viscerally invasive or rapidly progressing disease.

If RAI imaging shows no uptake, the NCCN recommends monitoring disease versus EBRT/IMRT. Radiation therapy can be considered upfront for patients with viscerally invasive or rapid progression. If RAI uptake is present, RAI treatment is preferred, followed by post-treatment ¹³¹I whole body imaging.

In patients with recurrent disease and widely metastatic disease, the tumor should be evaluated for actionable mutations such as ALK, NTRK, RET gene fusions, DNA mismatch repair (dMMR), micro-satellite instability (MSI), and tumor mutational burden (TMB). If found, they can be addressed with targeted therapies. ^[2]

For medullary thyroid carcinoma (MTC) without a RET mutation, NCCN treatment recommendations vary by tumor size. ^[2] For MTC < 1 cm, the NCCN recommends total thyroidectomy, with consideration of level IV neck dissection. For MTC ≥ 1 cm, recommended treatment is as follows:

• Total thyroidectomy with bilateral central neck dissection (level IV)
• Therapeutic ipsilateral or bilateral modified neck dissection (level II-V) for clinically/radiographically identifiable disease
• Consider prophylactic ipsilateral modified neck dissection for gross disease in adjacent central neck
• For surgically inaccessible residual disease, consider EBRT/IMRT

Patients should have postoperative levothyroxine to normalize TSH

For treatment of MTC related to MEN2B, NCCN recommendations are as follows:

• Total thyroidectomy during first year of life or at diagnosis
• Therapeutic neck dissection as indicated plus consideration of prophylactic bilateral central neck dissection
• If a tumor > 0.5 cm present, consider level II-V dissection
• Postoperative levothyroxine

For treatment of MTC related to MEN2A, NCCN recommendations are as follows:

• If patient does not have primary hyperparathyroidism, total thyroidectomy by age 5 or when identified (if older); if elevated calcitonin, elevated CEA, or abnormal nodes on US, therapeutic ipsilateral or bilateral central neck dissection
• Consider prophylactic ipsilateral modified neck dissection for gross disease in adjacent central neck; if tumor > 1 cm present, consider level II-V dissection
• Postoperative levothyroxine
• In patients with primary hyperparathyroidism, treatment is as above; in addition, during parathyroid exploration if a single adenoma is present, excise, and if involvement is multi-glandular, auto-transplant or leave equivalent size of one normal parathyroid gland;  consider cryopreservation of parathyroid tissue

Prior to thyroid surgery, pheochromocytoma removal by laparoscopic adrenalectomy is recommended, along with preoperative treatment with alpha-adrenergic blockade (phenoxybenzamine) or alpha-methyltyrosine to avoid a hypertensive crisis during surgery.

As with many other aggressive cancers, the treatment approach for anaplastic thyroid cancer (ATC) has benefited from a better understanding of specific tumor characteristics and the development of targeted chemotherapeutics. Given the aggressive nature and relatively poor outcomes with this cancer, guidelines recommend a prompt evaluation of tumor and a multidisciplinary discussion with surgeons, oncologists, palliative care specialists, and the patient. In particular, the potential for rapid airway and vascular compromise make early evaluation critical.

For staging, patient should undergo fluorodeoxyglucose (FDG) PET/CT or dedicated body CT or MRI. Patients with stage IVA or IVB disease who wish to pursue surgery can undergo complete resection (R0 or R1) with early adjuvant therapy to follow. Importantly, surgical planning must take into account the need to limit wounds that might lead to complications that would prevent early chemotherapy and radiation therapy. ^[18] Following surgery for stage IVA/IVB disease, patients should undergo definitive-intention radiation therapy with chemotherapy (taxane monotherapy or a taxane in combination with a platinum agent or anthracycline). ^[12]

Patients with stage IVB ATC, even if resectable, and stage IVC ATC who desire aggressive care should undergo genetic testing for actionable mutations, including BRAF V600E, ALK, NTRK, RET fusions, which may guide selection of targeted therapy with tyrosine kinase inhibitors. In some cases of stage IVB ATC, such targeted therapy can allow surgery for previously unresectable disease. ^[12] Stage IVC ATC that tests negative for those mutations can also be evaluated for high programmed death ligand 1 (PD-L1) expression, as these patients may be candidates for checkpoint inhibitor therapy.

Patients with stage IVC ATC can also opt for early palliative chemotherapy and/or radiation, as they will not be candidates for surgical resection. Close communication with patients and their family is important in these cases, as many individual factors may enter into the choice between palliative therapies or more aggressive care. ^[12]

 

NCCN recommendations for treatment of recurrent or metastatic thyroid disease include external beam radiation therapy (EBRT), with consideration of systemic therapy for tumors that have all the following characteristics ^[2] :

• Not resectable
• Not responsive to radioiodine ( ¹³¹I) therapy
• Not amenable to EBRT
• Showing significant disease progression

Oral kinase inhibitors (eg, vandetanib) are associated with longer progression-free survival but are not curative; side effects that may have a significant effect on quality of life should be considered. Kinase inhibitor therapy may not be appropriate for symptomatic patients with indolent disease. ^[2]

For recurrent disease and widely metastatic disease, the tumor should be evaluated for actionable mutations such as ALK, NTRK, RET gene fusions, DNA mismatch repair (dMMR), micro-satellite instability (MSI), and tumor mutational burden (TMB). This may guide use of targeted therapy. ^[2]

American Thyroid Association (ATA) guidelines on management of thyroid disease during pregnancy and the postpartum include the following recommendations on thyroid nodules and cancer in these patients ^[19] :

• ·For women with suppressed serum thyroid-stimulating hormone (TSH) levels that persist beyond 16 weeks gestation, fine-needle aspiration (FNA) of a clinically relevant thyroid nodule may be deferred until after pregnancy. At that time, if serum TSH remains suppressed, a radionuclide scan to evaluate nodule function can be performed if the woman is not breastfeeding
• There is insufficient evidence to recommend for or against routine measurement of serum calcitonin in pregnant women with thyroid nodules.
• Thyroid nodule FNA is generally recommended for newly detected nodules in pregnant women with a nonsuppressed TSH. Determination of which nodules require FNA should be based on the nodule's sonographic pattern. The decision whether to perform FNA during gestation or early postpartum may be influenced by the clinical assessment of cancer risk or by patient preference.
• Radionuclide scintigraphy or radioiodine uptake determination should not be performed during pregnancy.
• Pregnant women with cytologically benign thyroid nodules do not require special surveillance strategies during pregnancy and should be managed according to the ATA guidelines for adults iwth thyroid nodules and differentiated thyroid cancer.
• Pregnant women with cytologically indeterminate nodules, in the absence of cytologically malignant lymph nodes or other signs of metastatic disease, do not routinely require surgery while pregnant.
• Surgery may be considered during pregnancy if there is clinical suspicion of an aggressive behavior in cytologically indeterminate nodules.
• Molecular testing is not recommended for evaluation of cytologically indeterminate nodules during pregnancy. 
• Papillary thyroid cancer detected in early pregnancy should be monitored sonographically. If it grows substantially before 24–26 weeks gestation, or if cytologically malignant cervical lymph nodes are present, surgery should be considered during pregnancy. However, if the disease remains stable by midgestation, or if it is diagnosed in the second half of pregnancy, surgery may be deferred until after delivery.
• The impact of pregnancy on newly diagnosed medullary carcinoma or anaplastic cancer is unknown. However, a delay in treatment is likely to adversely affect outcome, so surgery should be strongly considered, after assessment of all clinical factors.

Recommendations for subsequent pregnancy in women with thyroid cancer include the following:

• Pregnancy should be deferred for 6 months after a woman has received therapeutic radioactive iodine ( ¹³¹I) treatment.
• In women with thyroid cancer who become pregnant, the TSH goal should remain the same as determined preconception. TSH should be monitored approximately every 4 weeks until 16–20 weeks of gestation, and at least once between 26 and 32 weeks of gestation.
• Women with previously treated differentiated thyroid cancer who have undetectable serum thyroglobulin (Tg) levels (in the absence of Tg autoantibodies) and are classified as having no biochemical or structural evidence of disease prior to pregnancy do not require ultrasound and Tg monitoring during pregnancy.
• Women diagnosed with papillary thyroid microcarcinoma who are under active surveillance should have ultrasound monitoring of their thyroid performed each trimester during pregnancy.