Long-Term Locoregional Control With Unilateral Radiation for AJCC-7 T1-2N2b Tonsillar Cancer.

<bold>Purpose/objective(s): </bold>Given the historical toxicity of radiotherapy for head & neck cancer, there has been an emphasis on de-escalation for patients with favorable disease features. The use of unilateral radiation to cervical nodes is a prominent de-escalation strategy in well-lateralized tonsil cancers. However, the safety of this approach for patients with AJCC-7 N2b disease was less well-established in the landmark studies guiding its use. The study hypothesis was that unilateral radiation for AJCC-7 T1-2N2b tonsillar cancer results in a low rate of contralateral nodal failure.<bold>Materials/methods: </bold>This study was a retrospective chart review of 66 patients treated from 2005 to 2016 at two academic institutions. Eligible patients had AJCC-7 T1-2N2b squamous cell carcinoma of the tonsil and were treated with unilateral radiation therapy. The primary endpoint was the rate of contralateral nodal failure at the time of last follow-up. Ipsilateral recurrence rates and overall survival were additional endpoints of interest. When available, data were collected regarding the presence of clinical extracapsular extension (ECE). Human papillomavirus/p16 status was also assessed.<bold>Results: </bold>The median age at diagnosis was 55.5 years and 53 patients (80.3%) were male. 38 patients (57.6%) had T1 disease and 28 patients (42.4%) had T2 disease based upon AJCC-7 staging. Of the 52 patients who had information on tumor HPV status, all were positive. In regards to systemic therapy, 18 patients (27.3%) had induction therapy, 26 (39.4%) had concurrent therapy, and 4 (6.1%) had both. The median time to last post-radiation follow-up was 80.9 months; 87.9% of patients remained alive at last follow-up and median OS was not reached. Contralateral nodal failure occurred in 2/66 (3.0%) patients at 3.6 and 20.9 months, respectively. Both patients underwent salvage treatment. The first survived an additional 65 months and the second remains alive at last follow-up 37 months after recurrence. Sixteen patients (24.2%) were felt to have extracapsular extension by clinical exam, radiology, or pathology; one of the two contralateral recurrences occurred in this group. Two patients (3%) experienced recurrence at the treated primary site and/or neck. Overall locoregional control at both 2 and 5 years was 93.9% and the median duration of control was not reached.<bold>Conclusion: </bold>The use of unilateral radiation for AJCC-7 T1-2N2b tonsillar cancer resulted in low rates of contralateral nodal failure. This outcome demonstrates the safety of considering unilateral treatment in patients with a high ipsilateral nodal burden. Further assessments are needed to determine the impact of radiation volume reduction on patient quality of life. [ABSTRACT FROM AUTHOR]