LAUSR

e15071 Background: To determine if anal cancer patients with HPV positive disease have different overall survival (OS) compared to those with HPV negative disease, and to elucidate differences in the association between radiation dose and OS. Methods: We utilized the National Cancer Database (NCDB) registry to identify a cohort of non-metastatic anal cancer patients treated with curative intent between 2008 – 2015. Propensity score matching was used to account for potential selection bias between patients with HPV positive and negative disease. Multivariable Cox regression was used to determine the association between HPV status and OS. Kaplan-Meier methods were used to compare actuarial survival estimates. Results: We identified 5,927 patients with tumor HPV status for this analysis, 3,523 (59.4%) had HPV positive disease and 2,404 (40.6%) had HPV negative disease. Propensity-matched analysis demonstrated that patients with HPV positive locally advanced (T3-4 or node positive) anal cancer had better OS (HR=0.81 (95%CI: 0.68-0.96), p=0.018). For patients with early stage disease (T1-2 and node negative) there was no difference in OS (HR=1.11 (95%CI:0.86-1.43), p=0.43). In the unmatched cohort, there was an increase in 3-year OS for patients with HPV positive tumors or early stage disease up to 45-49.9 Gy (p<0.001), whereas for patients with HPV negative and locally advanced disease there was an increase in survival from 46% at 30-44.9 Gy, to 64% at 45-49.9 Gy (p=0.093) and further to 71% at 50-54.9 Gy (p=0.005). Conclusions: We found HPV to be a significant prognostic marker in anal tumors, especially for locally advanced disease. We further found that higher radiation dose up to 50-55 Gy was associated with better OS, mainly for locally advanced disease in HPV negative patients. Multivariable Cox proportional hazards regression for OS. [Table: see text]