Malignant Tumors of the Base of Tongue 

Updated: Apr 05, 2021
Author: Rishi Sethia, MD; Chief Editor: Arlen D Meyers, MD, MBA 

Overview

Practice Essentials

The oropharynx is a common location of upper aerodigestive tract malignancies, and each subsite of the oropharynx, including the base of tongue, has different diagnostic, therapeutic, and prognostic characteristics. The majority of base of tongue malignancies are squamous cell carcinomas (SCCs), but other malignant processes can arise, including lymphoepithelial carcinomas, hematolymphoid tumors, salivary gland tumors, and mucosal melanomas.[1]  (See the images below.)

A sagittal computed tomography (CT) scan of the ne A sagittal computed tomography (CT) scan of the neck with contrast demonstrates a pedunculated soft tissue lesion at the left base of the tongue without invasion of the floor of the mouth or adjacent structures. The mass measures approximately 2.7 x 1.8 x 2.8 cm.
An axial CT scan of the neck with contrast again d An axial CT scan of the neck with contrast again demonstrates a soft tissue left base of tongue lesion with slight extension into the glossotonsillar sulcus. There is also an enlarged, pathologic-appearing, left level II cervical lymph node.

Historically, tobacco and/or alcohol use were the primary risk factors for oropharyngeal tumors. However, there has been a significant change in the epidemiology of base of tongue tumors, with a substantial increase in human papillomavirus (HPV)–associated oropharyngeal SCC. Fortunately, patients with these HPV-associated tumors have a much better response to treatment and improved prognosis compared with individuals with traditional, non-HPV oropharyngeal SCCs.[2, 3]  It is estimated that overall, oropharyngeal SCCs will make up about 47% of all head and neck cancers in the United States by 2030.[4]  

Careful multidisciplinary assessment of base of tongue tumors is paramount for appropriate treatment, which is based on staging, pathology, tumor location, functional outcomes, and patient preference. Survival and prognosis depend on early detection and initial staging of the disease. Because of the nonspecific nature of associated symptoms, however, patients with base of tongue tumors may present with advanced disease. Moreover, the disease process and associated treatment modalities can often affect adjacent upper aerodigestive structures, which impacts speech, swallowing, and quality of life (QOL).

Despite the complex anatomy associated with base of tongue tumors, as well as concerns regarding posttreatment functional deficits, significant changes in management options for such neoplasms have vastly improved outcomes in recent years.

Workup in malignant tumors of the base of tongue

Imaging

Cross-sectional imaging is an important tool for the diagnosis and clinical staging of malignant tumors of the tongue base. High-resolution computed tomography (CT) scanning of the neck with intravenous (IV) contrast is the most commonly utilized modality and has the advantages of increased availability and speed, with excellent spatial resolution, demonstration of bone infiltration, and lymph node visualization.

Magnetic resonance imaging (MRI) of the neck is more costly but can be utilized as an alternative to neck CT scanning.

Positron emission tomography (PET) scanning with CT imaging is used in the evaluation of unknown primary tumors, synchronous primary tumors, and distant metastases.[5]

Biopsy

Biopsy via endoscopic examination of the primary site with the patient under anesthesia remains the definitive procedure to establish the diagnosis and accurately assess the primary tumor.

Management of malignant tumors of the base of tongue

The decision to use surgical excision and other treatment modalities for malignant base of tongue tumors is primarily based on pathology, initial staging, tumor location, medical comorbidities, smoking history, and patient preference. Other important considerations include a patient's overall health and the individual's ability to tolerate prolonged intraoperative anesthesia versus chemotherapy and radiation therapy. Depending on the extent of surgery required and the potential need for reconstruction, patients may require a temporary nasogastric feeding tube and/or tracheostomy tube in order to maintain adequate nutrition and protect the airway. Additionally, tumors may be considered unresectable because of their size/location or the extent of the disease or due to invasion into critical structures.

Early stage base of tongue SCC can be treated with surgical therapy and/or radiation. Advanced-staged tumors may be treated surgically with adjuvant radiation/chemoradiation versus definitive chemoradiation. Advances in surgical techniques, including endoscopic and transoral laser/robotic approaches, as well as free tissue transfers for reconstructive surgery, have decreased the morbidity historically associated with base of tongue surgery. Most recent guidelines from the National Comprehensive Cancer Network (NCCN) require p16 testing for the presence of HPV, consequently changing the treatment recommendations for and staging of these tumors.

Background

The oropharynx is a common location of upper aerodigestive tract malignancies, and each subsite of the oropharynx, including the base of tongue, has different diagnostic, therapeutic, and prognostic characteristics. The majority of base of tongue malignancies are squamous cell carcinomas (SCCs), but other malignant processes can arise, including lymphoepithelial carcinomas, hematolymphoid tumors, salivary gland tumors, and mucosal melanomas.[1]  (See the images below.)

A sagittal computed tomography (CT) scan of the ne A sagittal computed tomography (CT) scan of the neck with contrast demonstrates a pedunculated soft tissue lesion at the left base of the tongue without invasion of the floor of the mouth or adjacent structures. The mass measures approximately 2.7 x 1.8 x 2.8 cm.
An axial CT scan of the neck with contrast again d An axial CT scan of the neck with contrast again demonstrates a soft tissue left base of tongue lesion with slight extension into the glossotonsillar sulcus. There is also an enlarged, pathologic-appearing, left level II cervical lymph node.

Historically, tobacco and/or alcohol use were the primary risk factors for oropharyngeal tumors. However, there has been a significant change in the epidemiology of base of tongue tumors, with a substantial increase in human papillomavirus (HPV)–associated oropharyngeal SCC. Fortunately, patients with these HPV-associated tumors have a much better response to treatment and improved prognosis compared with individuals with traditional, non-HPV oropharyngeal SCCs.[2, 3]  It is estimated that overall, oropharyngeal SCCs will make up about 47% of all head and neck cancers in the United States by 2030.[4]  

Careful multidisciplinary assessment of base of tongue tumors is paramount for appropriate treatment, which is based on staging, pathology, tumor location, functional outcomes, and patient preference. Survival and prognosis depend on early detection and initial staging of the disease. Because of the nonspecific nature of associated symptoms, however, patients with base of tongue tumors may present with advanced disease. Moreover, the disease process and associated treatment modalities can often affect adjacent upper aerodigestive structures, which impacts speech, swallowing, and quality of life (QOL).

Despite the complex anatomy associated with base of tongue tumors, as well as concerns regarding posttreatment functional deficits, significant changes in management options for such neoplasms have vastly improved outcomes in recent years.

Management of malignant tumors of the base of tongue

The decision to use surgical excision and other treatment modalities for malignant base of tongue tumors is primarily based on pathology, initial staging, tumor location, medical comorbidities, smoking history, and patient preference. Other important considerations include a patient's overall health and the individual's ability to tolerate prolonged intraoperative anesthesia versus chemotherapy and radiation therapy. Depending on the extent of surgery required and the potential need for reconstruction, patients may require a temporary nasogastric feeding tube and/or tracheostomy tube in order to maintain adequate nutrition and protect the airway. Additionally, tumors may be considered unresectable because of their size/location or the extent of the disease or due to invasion into critical structures.

Early stage base of tongue SCC can be treated with surgical therapy and/or radiation. Advanced-staged tumors may be treated surgically with adjuvant radiation/chemoradiation versus definitive chemoradiation. Advances in surgical techniques, including endoscopic and transoral laser/robotic approaches, as well as free tissue transfers for reconstructive surgery, have decreased the morbidity historically associated with base of tongue surgery. Most recent guidelines from the National Comprehensive Cancer Network (NCCN) require p16 testing for the presence of HPV, consequently changing the treatment recommendations for and staging of these tumors.

Etiology

Chronic alcohol use and prolonged tobacco consumption, including smokeless tobacco use, are traditional and synergistic risk factors for head and neck malignancies such as base of tongue SCC.[6, 7]  HPV infection is another significant risk factor and is closely associated with the rise in oropharyngeal SCC cases, especially among healthy, middle-aged Caucasian males. A meta-analysis by Mehanna et al showed a drastic and significant increase in the overall prevalence of HPV-positive oropharyngeal SCC over time, as follows[8] :

  • Before 2000 - 40.5%
  • 2000-2004 - 64.3%
  • 2005-2009 - 72.2%

Persistent oral HPV infection is the most likely precursor for the development of HPV-associated oropharyngeal SCC, but the pathophysiology of the disease and how it arises from the initial infection are still unclear.[9, 10, 3]  Some studies have suggested that sexual history, including engagement with multiple sexual partners and in oral sex, is associated with HPV infection and the risk of HPV-associated SCC.[11, 12]  Among the oncogenic HPV subtypes that have been identified in oropharyngeal SCCs, the high-risk subtype 16 has been found to be present in 90% of them.[1, 13]

Pathophysiology

The tongue is a vital organ that plays a critical role in speech, taste, mastication, and swallowing. During the oral phase of swallowing, food and liquid are propelled toward the oropharynx from the oral cavity by the tongue. During the subsequent pharyngeal phase, the tongue seals the oropharynx and the vocal cords close while the epiglottis moves to cover the laryngeal vestibule. The larynx elevates in the process and moves anteriorly. These key motions are important in protecting the airway from aspiration.

Alterations in tongue and pharynx mobility can result in altered speech, while surgical resection and/or adjuvant radiation treatment of the base of tongue may lead to dysphagia and odynophagia. Due to posttreatment changes in swallowing, it is recommended that most patients with a base of tongue tumor who have undergone surgery and/or radiation therapy be seen and evaluated by speech and language pathologists in the pretreatment and posttreatment settings.

Presentation

Dysphagia, odynophagia, foreign body sensation, referred otalgia, oral bleeding, and a neck mass are the most common clinical manifestations for base of tongue tumors. Patients may present in a delayed fashion and with advanced disease due to the vague nature of the symptoms and their relatively late appearance (which can be attributed to the limited number of free nerve endings in the base of tongue). Patients with advanced disease can also present with obstructive symptoms, including dyspnea, and an inability to tolerate secretions when the tumor has spread to surrounding structures.

A detailed and thorough base of tongue examination may be difficult to perform owing to inadequate visualization, unavailability of appropriate equipment, poor patient compliance (ie, strong gag reflex), and the submucosal presence of disease. Indirect or flexible fiberoptic laryngoscopy in the office is a useful adjunct to the physical examination.

Patients may have bilateral palpable adenopathy because of the proximity of the disease to midline and a high propensity for regional lymph node metastases.

Relevant Anatomy

The base of tongue is bound anterior-superiorly by the circumvallate papillae, posterior-inferiorly by the vallecula, and laterally by the glossopalatine sulci. However, since there is a lack of distinct anatomic boundaries, primary tumors of the base of tongue can easily spread from this oropharyngeal subsite to other areas, including the oral cavity, nasopharynx, and larynx. The base of tongue is part of Waldeyer's ring within the oropharynx and contains a rich, intricate lymphatic network.[1]  Despite this, oropharyngeal tumors characteristically drain to clinical neck levels II, III, and IV, with possible spread to other regions with extensive disease.[14, 15, 16]  Base of tongue tumors have a higher incidence of metastatic spread to bilateral cervical lymph nodes primarily because of the tumors' proximity to midline but also due to known contralateral lymphatic drainage.[17]  A thorough understanding of lymphatic drainage patterns based on the primary tumor's size and location is critical when determining surgical and/or adjuvant treatment options. Malignancies of the base of tongue require that both sides of the neck be addressed.

The blood supply of the tongue is based off the lingual artery and has complex capillary and venous systems. Sensory and taste innervation for the base of tongue is primarily provided by the glossopharyngeal nerve, although such innervation is provided to the most posterior-inferior aspect by the internal branch of the superior laryngeal nerve.[1]  Tongue musculature includes both intrinsic and extrinsic muscles, which contribute to the varied and subtle movements involved in speech, mastication, and swallowing. The muscles are served by efferent motor fibers from the hypoglossal nerve; the exception is the palatoglossus muscle, which is innervated by the vagus nerve.

Because the mucosa of the base of tongue contains squamous epithelium, minor salivary glands, and lymphoid tissue, malignant neoplasms may arise from any of these tissues.

 

Presentation

History

As in all head and neck cancers, it is essential to gather a thorough history, with an emphasis on common risk factors such as tobacco and alcohol use. Patients with base of tongue tumors may present with dysphagia, odynophagia, foreign body sensation, referred otalgia, oral bleeding, or a neck mass. In advanced disease, patients can present with obstructive symptoms such as dyspnea and inability to tolerate secretions. General health status, including cardiac and pulmonary history, previous surgery or radiation treatment, and use of anticoagulation therapy, are also important to evaluate given the potential implications on treatment and outcomes.

Physical Examination

A comprehensive head and neck examination is recommended for all patients, including detailed cranial nerve examination and palpation of the neck to assess for regional metastatic lymphadenopathy. Inspection and palpation of the tongue base may be limited by inadequate access to equipment, poor patient compliance, or submucosal extent of disease. Office indirect or flexible fiberoptic laryngoscopy is a useful adjunct to the physical examination.

 

Workup

Laboratory Studies

HPV testing with p16 immunohistochemistry is now required for all newly diagnosed base of tongue SCCs, with p16 overexpression being strongly associated with high-risk HPV. Additional HPV testing via in situ hybridization or polymerase chain reaction (PCR) assay can be utilized to clarify HPV status, if warranted.[18, 19]

Imaging Studies

CT scanning and MRI

Cross-sectional imaging is an important tool for the diagnosis and clinical staging of malignant tumors of the tongue base. High-resolution computed tomography (CT) scanning of the neck with intravenous (IV) contrast is the most commonly utilized modality and has the advantages of increased availability and speed, with excellent spatial resolution, demonstration of bone infiltration, and lymph node visualization. CT scanning of the chest is often obtained in addition to neck CT imaging as standard protocol for staging purposes, to assess for pulmonary metastases.

Magnetic resonance imaging (MRI) of the neck is more costly but can be utilized as an alternative to neck CT scanning. In certain instances, it is the preferred modality for deeply invasive malignancies, offering superior soft tissue evaluation and multiplanar capabilities.[20]  

PET/CT scanning

Positron emission tomography (PET) scanning with CT imaging is used in the evaluation of unknown primary tumors, synchronous primary tumors, and distant metastases.[5]  For surveillance following treatment of oropharyngeal cancer, PET/CT scanning is the most sensitive and specific imaging modality and plays an important prognostic role, especially when obtained between 3-6 months and 12 months posttreatment.[21]  (See the image below.)

An axial positron emission tomography (PET) scan s An axial positron emission tomography (PET) scan shows asymmetrical hypermetabolic uptake within the left base of the tongue/tonsillar region consistent with a primary tumor. Intense hypermetabolic left cervical lymphadenopathy is also seen and is concerning for metastatic disease.

Ultrasonography

Ultrasonography (US) offers distinct advantages as an inexpensive, radiation-free, real-time modality that can be used for evaluation of cervical lymphadenopathy and is potentially useful for guidance of fine-needle aspiration (FNA). However, the previously mentioned imaging modalities are favored for a comprehensive assessment.

Diagnostic Procedures

Biopsy via endoscopic examination of the primary site with the patient under anesthesia remains the definitive procedure to establish the diagnosis and accurately assess the primary tumor. Panendoscopy including direct laryngoscopy and esophagoscopy is often performed to assess for the extent of the lesion and to rule out secondary primaries, in order to help determine therapeutic management options. If lymphadenopathy is discovered on examination or imaging, FNA can provide a minimally invasive and expedited diagnosis as well.

Histologic Findings

The most common malignant neoplasm of the base of the tongue is SCC. The World Health Organization (WHO) classifies oropharyngeal SCC as HPV-positive or HPV-negative. HPV-associated oropharyngeal SCC frequently lacks keratinization and mature squamous differentiation, unlike the traditional, keratinizing SCC associated with tobacco and alcohol use.[22]

Other, less common malignancies include salivary gland tumors such as mucoepidermoid carcinoma, adenoid cystic carcinoma, and polymorphous adenocarcinoma, and hematolymphoid tumors, which include various forms of lymphoma.[23]  Rarely, lymphoepithelial carcinoma, soft tissue tumors, small cell neuroendocrine carcinoma, adenocarcinoma, or metastatic lesions can be found in the base of tongue.[1, 22]

Extranodal non-Hodgkin lymphoma of the head and neck is a relatively uncommon disease. If the nasopharynx (16% of the lymphomas), tonsils (12%), and base of tongue (8%) are grouped together, this combined site (Waldeyer's ring) becomes the most common location of the disorder (36%).[24]  Most Waldeyer's ring lymphomas express the B-cell phenotype. The clinical features and immunohistologic findings suggest that Waldeyer's ring lymphomas, other than those of the nasopharynx, share some of the characteristics of mucosa-associated lymphoid tissue lymphomas.

In difficult cases, detection of monoclonal immunoglobulin, an absence of keratin staining, and a lack of epithelial features based on electron microscopy findings are useful adjuncts for diagnosis. Three fourths of the patients have stage I or II disease, and approximately two thirds of them have intermediate-grade lymphoma. Patients with lymphomas of high histopathologic grade and recurrent and disseminated disease have the poorest prognosis.[24]

Staging

The American Joint Committee on Cancer (AJCC) utilizes the tumor, node, metastasis (TNM) system to stage oropharyngeal carcinoma based on the size of the primary site tumor, involvement of adjacent structures, involvement of regional lymph nodes (LNs), and presence of distant metastasis. Moreover, HPV (p16) status was incorporated into the eighth edition of the AJCC Cancer Staging Manual. The staging system for oropharyngeal carcinoma, as contained in the manual's eighth edition, is outlined below.[25]

All measurements listed below are in greatest dimension.

Primary tumor (T)

See the list below:

  • T1 - ≤2 cm
  • T2 - >2 cm but ≤4 cm
  • T3 - >4 cm or extension to lingual surface of epiglottis

Non–HPV-associated (p16-negative)

  • T4a - Moderately advanced local disease; invades adjacent structures (larynx, tongue muscles, medial pterygoid muscle, hard palate, mandible) or beyond
  • T4b - Very advanced local disease; invades lateral pterygoid muscle, pterygoid plates, lateral nasopharynx, skull base, or carotid artery encasement

HPV-associated (p16-positive)

  • T4 - Moderately advanced local disease; invades adjacent structures (larynx, tongue muscles, medial pterygoid, hard palate, mandible) or beyond

Regional lymph nodes (N)

See the list below:

  • Nx - Regional lymph nodes cannot be assessed
  • N0 - No regional lymph node (LN) metastasis

Non–HPV-associated (p16-negative)

  • N1 - Metastasis in single ipsilateral LN ≤3 cm and extracapsular extension (ECE)–negative
  • N2a - Metastasis in single ipsilateral LN >3 cm but ≤6 cm and ECE-negative
  • N2b - Metastasis in multiple ipsilateral LNs, none >6 cm, and ECE-negative
  • N2c - Metastasis in bilateral or contralateral LNs, none >6 cm, and ECE-negative
  • N3a - Metastasis in LN >6 cm and ECE-negative
  • N3b - Metastasis in any LNs and clinically overt ECE-positive

HPV-associated (p16-positive)

Clinical staging

  • N1 - 1+ ipsilateral LNs, ≤6 cm
  • N2 - Contralateral or bilateral LNs, ≤6 cm
  • N3 - Any LN(s) >6cm

Pathologic staging

  • N1 - Metastasis in ≤4 LNs
  • N2 - Metastasis in >4 LNs

Distant metastasis (M)

See the list below:

  • Mx - Distant metastasis cannot be assessed
  • M0 - No distant metastasis
  • M1 - Distant metastasis
 

Treatment

Medical Therapy

Treatment for patients with malignant neoplasms of the base of tongue depends on various factors. These include the pathology, histology, and immunohistochemical staining results (p16 status in SCC); the clinical stage of the neoplasm; the patient's age and associated medical conditions; patient compliance; potential adverse effects or complications; and expected outcomes. In order to allow the patient to make a reasonable and informed decision regarding treatment options, these factors must be discussed in detail before therapy.

As is true with other sites of the head and neck, early stage base of tongue SCC can be addressed via surgical treatment and/or radiation therapy (RT). Advanced-stage tumors may be treated surgically with adjuvant RT/adjuvant concurrent chemoradiation therapy (CRT) or with definitive CRT. The typical regimen for the early and advanced-stage lesions involves 6 weeks of RT and includes a platinum-based chemotherapy agent. More recently, there have been questions regarding the efficacy of using an epidermal growth factor receptor (EGFR) inhibitor, such as the monoclonal antibody agent cetuximab, in this setting.[26, 27]

In appropriately selected patients, CRT provides an effective treatment option and obviates the need for surgical intervention. However, RT and CRT can induce toxicity and significantly alter quality of life (QOL), as patients may experience xerostomia, mucositis, speech issues, dysphagia, aspiration, or respiratory distress requiring gastrostomy or tracheostomy placement.[28]  Concurrent CRT with brachytherapy has also been reported for base of tongue SCC, although limited evidence exists to support this treatment option outside of selected patients.[29]  Several trials examining treatment de-escalation and alteration of CRT regimens for HPV-associated oropharyngeal SCC are ongoing in an effort to minimize morbidities.[30]

Immunotherapy treatments with immune checkpoint inhibitors such as pembrolizumab and nivolumab are being investigated in numerous trials but are currently mostly reserved for palliative use in refractory oropharyngeal SCC. As the knowledge surrounding these treatments continues to evolve, immunotherapy could play a promising role in the management of oropharyngeal SCC.[31, 32]

Surgical Therapy

Surgical excision is based on initial staging, pathology, tumor location, and patient preference. The patient's overall health and ability to tolerate prolonged intraoperative anesthesia must also be taken into account. Depending on the tumor location, anticipated type of surgical resection and reconstruction, and potential need for adjuvant therapy, patients may require a temporary feeding tube and/or tracheostomy tube in order to maintain adequate nutrition and protect the airway, respectively. However, tumors may be considered unresectable because of their size/location, the extent of disease, or tumor invasion into critical structures. All of these factors must be considered when selecting an appropriate, definitive surgical therapy, medical therapy, or palliative management.

Non-SCCs in the form of malignant, solid tumor neoplasms of the base of tongue typically require a surgical approach. With hematologic malignancies like lymphoma, surgery only serves as a diagnostic modality; once a diagnosis is made, nonsurgical treatments (chemotherapy and/or radiation) are employed. SCC, on the other hand, requires a more thorough and thoughtful approach with regard to the appropriate treatment modality for each individual patient. Surgery, when elected, can be performed as the primary modality, with adjuvant therapy, or in the salvage setting with recurrent or persistent disease.

Depending on the size and location of the tumor, various surgical approaches can be applied. Traditionally, a translabial, transmandibular approach was used to remove malignant base of tongue tumors. Such surgery, however, involves significant morbidity, including lip and chin scars, malocclusion, compromised deglutition, chronic aspiration, altered speech articulation, and higher risk for delayed osteoradionecrosis of the mandible. Therefore, alternative techniques have been described, including transoral robotic surgery (TORS) and transoral laser microsurgery (TLM). These minimally invasive approaches have yielded favorable oncologic outcomes while decreasing the morbidity associated with traditional resection approaches.[33, 34, 35, 36, 37]  Numerous studies have supported improved QOL outcomes for TORS and TLM, especially in selected patients who undergo surgery alone.[38, 39, 40]

In patients with inadequate transoral access due to tumor location or difficult anatomy, lateral or transhyoid pharyngotomy may be required, in an open approach that avoids mandibulotomy.

Finally, in extensive lesions not amenable to the aforementioned approaches and in patients having recurrent or persistent disease after radiation or chemoradiation therapy, mandibular split is performed to provide wide access for surgical ablation, as well as reconstruction with vascularized tissue. In patients with large oropharyngeal defects, free flap reconstruction using microvascular anastomosis is the reconstruction method of choice. Typically, radial forearm or anterolateral thigh fasciocutaneous flaps are employed in this setting.

Given the proximity to midline of malignant tumors of the tongue base and the bilateral lymphatic drainage patterns, one must always treat both sides of the neck. With surgery, this typically involves performing bilateral neck dissections for locoregional disease control and accurate pathologic staging analysis. The risk of occult lymph node metastasis from the base of tongue is higher than from other oropharyngeal subsites, ranging from 21-45%.[41]  Thus, elective bilateral neck dissection is often performed with definitive surgical extirpation.

Follow-up

Although time intervals may vary by institution, patients with oropharyngeal cancer should undergo posttreatment surveillance for the first 5 years. Patients can be monitored beyond this time period depending on patient and clinician preferences; such continued monitoring can be especially important in high-risk patients such as those who continue to use tobacco. For example, patients can be monitored every 3 months for the first year, every 3-4 months for the second year, every 6 months for the third year, every 8 months for the fourth year, and yearly or as needed for the fifth year and beyond. PET/CT scanning is the most sensitive and specific imaging modality for posttreatment surveillance; imaging obtained between 3 and 6 months and 12 months after treatment has important prognostic implications. The likelihood of future recurrence is extremely low following two consecutive negative PET/CT-scan studies between 3 and 6 months posttreatment.[21]

Outcome and Prognosis

Although malignant tumors of the base of tongue have traditionally held a poor prognosis, there has been a sharp increase in HPV-positive oropharyngeal SCC in recent years,[4] and these patients have notably shown improved survival compared with patients with the HPV-negative form of the disease. One study reported 95% versus 62% 2-year overall survival rates in HPV-positive versus -negative patients, respectively,[42, 2]  with HPV-positive patients appearing to have improved treatment response rates compared with HPV-negative patients (84% vs 57%, respectively, after CRT).[42]  As the number of HPV-associated oropharyngeal SCC cases continues to rise, outcomes will continue to shift as research leads to more advanced understanding of and management strategies for these uniquely treatable malignant tumors.

In addition to epidemiologic contributions to improved outcomes, advances in technology and minimally invasive treatment options have reduced postoperative morbidity and improved prognosis. Numerous studies have demonstrated excellent oncologic outcomes with TLM and TORS, with functional and QOL benefits demonstrated. Grant et al revealed 2-year survival of 92% and 91% for T1 and T2 base of tongue SCCs treated with TLM, with high local control rates.[37]  De Almeida et al reviewed outcomes of 364 oropharyngeal SCC patients who underwent TORS and reported 2-year locoregional control, disease-specific survival, and overall survival rates of 92%, 94.5%, and 91%, respectively.[43]

Brachytherapy serves as a potential adjunct to treatment of base of tongue tumors, with one study revealing a 3-year overall survival rate of 80.9%, a locoregional control rate of 79.9%, and a disease-specific survival rate of 69.5%, when the therapy is combined with CRT.[29]

Adverse pathologic features such as positive margins, ECE, perineural invasion, lymphovascular invasion, and positive lymph nodes yield a worse prognosis and promote the use of adjuvant therapy to improve oncologic outcomes.[44, 45]

Future and Controversies

Multidisciplinary involvement is critical for appropriate evaluation and management of malignant tumors of the base of tongue. Clinicians are continually investigating how to minimize posttreatment functional deficits and QOL impairment while maintaining favorable oncologic outcomes. The expanded role of minimally invasive surgical modalities such as TORS/TLM, investigation into treatment de-escalation for HPV-associated tumors, and the emerging knowledge surrounding immunotherapy present exciting opportunities for the future.

Prevention

Although data is still emerging, HPV vaccination provides a unique opportunity to limit the recent surge in HPV-associated oropharyngeal SCC. Guidelines are expanding, and health officials are calling for early and widespread vaccination as a promising, feasible intervention to prevent HPV-associated oropharyngeal SCC.[46]