(OA29) Low Rate of Contralateral Neck Failure in T1-2N2B TONSIL PATIENTS Treated With Ipsilateral Neck Radiation

Abstract

Treatment of advanced oropharyngeal carcinomas generally entails bilateral radiation therapy. However, multiple single institutional retrospective studies have demonstrated low rates of contralateral neck failure in patients treated with radiation to the primary tumor and ipsilateral neck for well-lateralized tonsil cancer with N0-N2a (up to 1 lymph node, LN) disease. Avoidance of the contralateral neck results in both decreased acute and long-term side effects from treatment, however this reduction in radiation field must be balanced against the possibility of increased local recurrence There is little data specifically examining the possibility of omission of contralateral neck radiation in tonsil patients with N2b disease (>1 small LN). The purpose of our study is to review the institutional experiences at The University of Cincinnati and the University of Texas, MD Anderson Cancer Center in treating patients specifically with T1-T2N2b squamous cell carcinoma of the tonsil with ipsilateral neck irradiation to evaluate the rates of contralateral neck failure and assess treatment-related toxicities. We retrospectively reviewed the records of patients with squamous cell carcinoma of the tonsil who received definitive radiation between 1999 and 2017 at The MD Anderson Cancer Center and The University of Cincinnati. A total of 86 patients with T1-T2N2b were included and all other T and N stages were excluded. Of the 86 patients, 57 patients were p16+, 2 were p16 negative, and 27 had unknown p16 status. The rate of contralateral neck failure was determined. Radiation-related acute and late toxicities were documented. Of the 86 patients treated with ipsilateral radiation, 2 patients failed in the contralateral neck, for an absolute contralateral neck failure rate of 2.5%. One patient failed in the contralateral neck 3.6 months after treatment and the other patient failed in the contralateral neck at 21.1 months. There were no other contralateral failures after 21.1 months. The median follow-up was 78.7 months (range 3.4 – 205 months). Both of the contralateral neck failures were successfully salvaged. One patient underwent a salvage neck dissection followed by adjuvant ipsilateral neck radiotherapy and the other was salvaged with contralateral neck radiation. There were two patients with disease recurrence within the treatment field; one patient had persistent disease at the end of treatment and the second patient was found to have an in-field recurrence at 9 months. 33% received concurrent chemotherapy and 15% received induction chemotherapy. 7% required a feeding tube at the end of treatment. The contralateral neck failure rate in T1-T2N2b tonsil patients treated with ipsilateral neck RT is low. Feeding tube requirement is also low compared to historical controls from randomized trials (ranging from 15-50%). Moreover, both of the patients in our study who recurred within the contralateral neck were successfully salvaged. As multiple ongoing studies attempt to de-escalate treatment in the HPV+ oropharyngeal cancer population to reduce morbidities of treatment, our data supports decreasing the treatment volume in an effort to minimize toxicity. Ipsilateral neck irradiation should be considered in patients with well-lateralized T1-T2N2b tonsillar cancer, particularly those that are HPV+.