Prognostic Impact of Primary Tumor Extent and Postoperative Radiation Facility Location in Major Salivary Gland Malignancies

Introduction The treatment of primary salivary malignancies often requires a multimodality approach. The purpose of this analysis was to evaluate the interaction between primary tumor extent and the treatment location of postoperative radiotherapy (PORT) in patients with primary salivary malignancies with respect to survival outcomes. Methods Patients with primary salivary malignancies who underwent upfront surgery followed by radiation were queried in the National Cancer Database (NCDB). Patients were stratified by pathologic T stage and whether PORT was performed at the same or different facility as the definitive surgery. Survival outcomes were compared using the Kaplan-Meier method and Cox proportional hazards regression. Results A total of 5,553 patients were selected, of which 1,159 had pathologic T4 (pT4) tumors. Patients who received PORT at the same facility compared with a different facility demonstrated superior overall survival (OS) on log-rank analysis (p=0.003). On subgroup analysis, patients with pT4 tumors had superior OS (p=0.015), whereas patients with smaller T1-3 tumors did not. PORT receipt at the same surgical facility was not a significant predictor of OS on multivariable analysis when all patients were included (p=0.057). However, among patients with pT4 tumors, OS was improved in patients who got PORT at the same facility as their surgery (p=0.015), with 10-year survival rates of 38.3 (95% confidence interval (CI): 33%-44%) versus 31% (95%CI: 24%-38%). Conclusion OS was improved in patients with primary salivary malignancies who received PORT at the same facility as their surgery, but the difference appears to be primarily driven by patients with pT4 primary tumors.