Abstract only 3572 Background: Anal cancer is an uncommon malignancy with numerous factors that influence treatment outcomes. Historically, HIV+ patients were restricted from entering clinical trials, limiting data on their outcomes to small retrospective reports. This study seeks to understand the factors related to anal cancer outcomes, specifically the differences between HIV+ and HIV- patients. Methods: Inclusion criteria was non-metastatic anal squamous cell carcinoma treated with a definitive course of chemotherapy and radiation between 2005 and 2018 at a single institution. Clinical data related to baseline characteristics, treatment parameters, and post-treatment follow-up were extracted for calculation of freedom from local recurrence (FFLR) and overall survival (OS). Univariate analysis (UVA) and multivariate analysis (MVA) were done using cox proportional hazard model, and FFLR and OS were calculated using the Kaplan-Meier method. Results: During the study period, 111 patient initiated definitive treatment for anal cancer. Median age was 56.7 years (IQR: 51.4-63.5), and 47% (N = 52) were HIV+. At median follow-up of 28 months, 12 and 24-month FFLR was 84.1% and 78.2% respectively, with 24-month OS of 87.3%. MVA demonstrated significant association between FFLR and T-stage HR 4.02 (95% CI: 2.14-7.55) p < 0.001, elapsed treatment time (median of 50 days) 1.08 (95% CI: 1.04-1.12) p < 0.001, and diagnosis to treatment start (median time of 15 weeks) 1.05 (95% CI: 1.01-1.08) p = 0.005. Additional analysis with log-rank test for FFLR demonstrated significant difference between patients taking < 50 days to complete treatment (p = 0.03), and < 15 weeks from diagnosis to treatment completion (p = 0.006). In HIV+ patients, post-treatment CD4 < 150 was significantly associated with worse OS on log-rank test (p = 0.016), with pretreatment CD4 values being non-significant. Conclusions: This study represents the largest single institution report of HIV positive patients treated for anal cancer. No difference in local recurrence or overall survival between HIV+ and HIV- patients was elucidated; however, HIV+ patients with lower post-treatment CD4 counts had worse OS. The most significant predictors of local recurrence were advanced T-stage, increased time from diagnosis to treatment initiation, and prolonged treatment time.