Definitive Radiotherapy for Base of Tongue Squamous Cell Carcinoma

Purpose/Objective(s):To evaluate the long-term efficacy of primary radiation therapy in the management of base-of-tongue squamous cell carcinoma.Materials/Methods:We retrospectively reviewed the medical records of 468 patients treated curatively with definitive radiation therapy between 1964 and 2011 for base-of-tongue squamous cell carcinoma. Inclusion criteria included curative intent with definitive radiation, a completed course of radiation, a minimum of 2 years of potential follow up, and no distant metastasis at presentation. Median follow up for the cohort was 5.5 years (range, 0.2 to 29.3 years) for all patients and 8.7 years (range, 1.6 to 29.3) for living patients. Median total dose to the primary site was 74.4 Gy (range, 56.6 to 81.6). Various treatment strategies were used including once-daily standard fractionation in 87 patients (18 %), concomitant boost technique in 99 patients (21%), twice-daily fractionation in 268 patients (57%), and simultaneous boost technique in 14 patients (3%). Intensity-modulated radiotherapy was used in 128 patients (27%). Overall, 87% (409) of patients presented with positive cervical node involvement and 227 (48.5%) patients underwent planned neck dissections in addition to radiotherapy. Adjuvant chemotherapy was administered to 171 (37%) patients. Data regarding p16 pathway activation was only available for 5% of patients (25) in the current series. Toxicity was graded according to the Common Terminology Criteria for Adverse Events, v4.0.Results:The local control rate at 5 years for the entire cohort was 85%; when separated by T stage the local control rates at 5 years were as follows: T1, 97%; T2, 94%; T3, 86%; and T4, 65% (p<0.0001). Local regional control rates based on overall stage at 5 years were as follows: I-II, 96%; III, 83%; IVa, 88%; and IVb, 62% (p<0.0001). Overall survival rates at 5 years were as follows: I-II, 66%; III, 69%; IVa, 71%; and IVb, 36% (p<0.0001). Cause-specific survival rates at 5 years were as follows: I-II, 89%; III, 78%; IVa, 83%; IVb, and 48% (p<0.0001). The 5-year local-regional control rate for patients treated with IMRT vs. no IMRT were 88% and 77%, respectively (p=0.0120). Severe late radiation-related complications occurred in 68 (14.5%) patients.Conclusions:Our data reveal that the local-regional control rates and survival rates after definitive radiotherapy are acceptable. As our median follow up time increases, it is evident that late effects of radiation continue to burden patients even decades after treatment. As we begin to see an increasing number of patients with favorable tumor markers, we advocate for research into possible de-intensification of treatment for suitable patients to minimize serious late radiation effects.

SSE24-03

Definitive Radiotherapy for Base of Tongue Squamous Cell Carcinoma