Long Term Follow-Up from a Phase I/II Trial Utilizing a Dose-Escalated Stereotactic Radiosurgery (SRS) Boost for Unfavorable Locally Advanced Oropharyngeal Cancer

Abstract

Purpose/Objective(s): Patients with cervical lymphadenopathies of unknown primary carcinoma (CUP) usually undergo neck dissection and irradiation. There is an ongoing controversy regarding the extent of nodal and mucosal volumes to be irradiated. We assessed outcomes after bilateral or unilateral nodal irradiation. Materials/Methods: This retrospective multicentric study included CUPpatients undergoing radiotherapy between 2000 and 2015. Results: Of 350 patients, 74.5% had unilateral disease. Sixty-one (20.5%) patients had unilateral disease and unilateral irradiation, 155 (52.2%) unilateral disease and bilateral irradiation and 81 (27.3%) bilateral disease and bilateral irradiation. Thirty-four (9.7%) and 217 (62.0%) patients had neoadjuvant and/or concomitant chemotherapy, respectively. Median follow-up was 37 months. Three-year local, regional, locoregional failure rates and CUP-specific survival were 5.6%, 11.7%, 15.0%, and 84.7%, respectively. In patients with unilateral disease, the 3-year cumulative incidence of regional / local relapse was 7.7%/4.3% after bilateral irradiation versus 16.9%/11.1% after unilateral irradiation (pZ0.17/0.32). The cumulative incidence of cause-specific deaths was 9.2% after bilateral irradiation and 15.5% after unilateral irradiation (pZ0.92). In multivariate analysis, mucosal irradiation was associated with better local control; while neck dissection, N2b and interruption of radiotherapy for more than 4 days were associated with poorer regional control. Toxicity was higher after bilateral irradiation (p <0.05). PET-CT, largest node diameter, N2b, interruption of radiotherapy and neoadjuvant chemotherapy were associated with poorer cause specific survival. Conclusion: Bilateral nodal irradiation yielded non-significant better nodal and mucosal control rates but was associated with higher rates of severe toxicity.