Timing of postoperative radiation therapy and survival in resected salivary gland cancers: Long-term results from a single institution.

e18052 Background: Timely administration of postoperative radiation therapy (PORT) impacts oncologic outcomes in resected squamous cell carcinomas of the head and neck. Salivary gland cancers (SGCs) are uncommon, and timing of PORT has not been extensively explored. We aimed to determine if the interval between surgery and PORT impacts outcomes in SGCs. Methods: We retrospectively identified patients with SGCs who underwent curative intent surgical resection followed by adjuvant PORT at our tertiary referral center. Demographic, tumor, and treatment data were collected. Patients with non-oncologic resections and/or delay of > 6 months to radiation start were excluded. Locoregional control (LRC), relapse free survival (RFS), and overall survival (OS) were estimated using the Kaplan Meier method. A multivariate analysis explored the association between demographics, tumor characteristics, and PORT timing with oncologic outcomes using a stepwise Cox proportional hazards model. Results: Between 1/1/1997 and 12/31/2017 180 eligible patients were identified. Patient characteristics are described in Table. The median time to PORT start was 61 (range 8-121) days, 169 (93.9%) of patients received neutron beam PORT. With a median follow up of 8.2 years in surviving patients, the 5-year OS and LRC estimates were 73% and 67%, respectively. In a multivariate analysis, only nodal involvement, histologic grade, and age at diagnosis were associated with OS, while nodal involvement, tumor size, and age at time of diagnosis were associated with LCR and RFS. Time to PORT start or completion was not statistically associated with survival outcomes on multivariate analysis. Conclusions: SGC patients who underwent surgery in our tertiary institution received PORT within a median of 61 days after surgery. With long term follow up, PORT timing in this retrospective series was not associated with worse oncologic outcomes, and support timely administration of PORT with 3 months of surgical resection. Further work is necessary to assess generalizability of these results.[Table: see text]