The impact of radiotherapy, in addition to chemotherapy, on overall survival in the initial management of patients with newly diagnosed metastatic head and neck squamous cell carcinoma

6035 Background: The role of radiation therapy (RT) in the upfront management of patients with metastatic head and neck squamous cell carcinoma (HNSCC) is not clearly defined. In this study, we used the National Cancer Database (NCDB) to assess the association between RT use and overall survival (OS) for patients with metastatic HNSCC who received chemotherapy. Methods: We analyzed the NCDB to identify patients with newly diagnosed metastatic HNSCC from 2004-2013 who were treated with upfront chemotherapy. Associations between the use of RT and OS were evaluated using the Kaplan Meier method, univariate and multivariate cox regression, propensity score matching, and sequential landmark analysis. Survival outcomes were also compared for patients receiving a biologically effective dose (BED) ≥72 Gy10 and < 72 Gy10. Results: We identified 3,516 patients diagnosed with metastatic HNSCC who were treated with chemotherapy, of which 2,288 (65%) were also treated with RT. The median follow up was 11.9 months. The addition of RT to chemotherapy was associated with prolonged survival (median 13.6 v 11.3 months, logrank p < 0.001). On multivariate analysis, the use of RT remained associated with prolonged survival (HR = 0.71, 95% CI 0.61-0.82, p < 0.001). After propensity score matching, the addition of RT was associated with improved median survival (13.5 v 11.2 months) and 5-year (17% v 7%) OS compared to chemotherapy alone (log rank, p < 0·001). Landmark analyses limited to patients who survived at least 3, 6, and 12 months after diagnosis continued to demonstrate improved OS with the addition of RT. Among patients treated with RT, the use of RT schedules with a BED exceeding 72 Gy10 was associated with prolonged survival (median 18.0 versus 11.7 months, logrank p < 0.001). Conclusions: For patients with metastatic HNSCC, the addition of RT to chemotherapy was associated with improved OS in this population based study. These results provide rationale for prospective randomized trials to validate these findings and to determine the optimal radiation therapy dose/fractionation and treatment schedule for these patients.