Cancer of the base of the tongue poses a more difficult therapeutic problem than do tonsillar carcinomas. The 5-year survival rates are lower, metastases are more common, early diagnosis is less common, and treatment morbidity is greater. Because of the functional difficulties from wide local excision, even of small tongue-base cancers, most tumors are treated with definitive radiation. Three quarters of patients are first seen with stage III or IV disease, primarily because of the early development of regional metastases, even with T1 or T2 tumors. Understaging of the primary tumor is frequent because these cancers tend to be diffusely infiltrative beyond their clinical appearance. This may account for similarities in local tumor control rates for both early and advanced lesions. The poor outcome is largely attributable to late diagnosis.
The staging of tongue-base carcinomas is principally dependent on primary tumor size and the extent of regional metastases. Lymph node involvement is present in approximately 60% of patients with small (T1, T2) primaries and, as with all head and neck neoplasms, is the major determinant of prognosis. Overall 5-year survival rates range from 11% to 45%. The 5-year survival rates decrease from over 60% for N0 patients to less than 30% for N1 patients.
The results of radiation therapy alone as definitive treatment for small primary tumors (T1, T2) are better for exophytic than for deeply invasive tumors. Radiation alone is generally reserved for those patients without clinical node metastases, but can be combined with planned neck dissection for patients with clinically positive nodes that persist after the completion of radiation. Local recurrence is more frequent after radiation alone in most series, and salvage of local failure is poor. In selected patients, interstitial radiation therapy has been used to treat residual palpable disease after external beam radiation in anticipation of better local control. The use of brachytherapy is associated with high rates of soft tissue necrosis and osteoradionecrosis, however. The results of supplemental interstitial therapy appear to be highly dependent on the dose and technique, with the best results reported with extensive percutaneous lateral cervical loop implants to include treatment of the lateral oropharyngeal wall and pharyngoepiglottic fold. The acute morbidity with implantation techniques is severe and results in massive tongue edema that necessitates at least temporary tracheostomy in all patients. The use of twice-daily, hyperfractionated radiotherapy or concomitant chemotherapy and radiotherapy appears to result in improved tumor control without many of the complications associated with implants for the larger tumors.
Surgical management of small primary tongue-base tumors (T1) achieves results similar to those from radiation alone. In most cases, however, primary tumors are moderately advanced and require transcervical resection via mandibulotomy or lateral pharyngotomy approaches, combined with elective or therapeutic neck dissection. Because of high rates of nodal metastases, most of the patients will still require postoperative radiotherapy. Local tumor control rates are superior to those with radiation alone, but regional control is poor if clinically positive nodes are present. Elective neck dissection can serve an important role as a staging procedure, thereby providing a rationale for adjuvant radiation therapy. To date, no prospective randomized trial data are available that compare surgery alone with combined surgery with either pre- or postoperative radiation. Survival rates do not differ substantially by stage of disease for patients with tongue-base cancers, except for those with stage IV disease (