758 Background: A standard therapy for locally advanced rectal cancer (LARC) includes fluoropyrimidine (FP)-based neoadjuvant chemoradiation (nCRT). Previous studies have inconsistently demonstrated that baseline neutrophil- and platelet-to-lymphocyte ratios (NLR and PLR) are predictive of response to nCRT or prognostic of outcomes in LARC. Methods: We performed a review of patients with LARC undergoing nCRT followed by surgery with curative intent from 2005-2013 in 3 academic cancer centers from 2 Canadian provinces. Data regarding demographics, staging, baseline hematologic variables (<4 weeks prior/up to 2 weeks after initiating nCRT) and treatment details were collected. Outcome measures of interest were pathological complete response (pCR), disease-free survival (DFS) and overall survival (OS). Logistic regression and Cox proportional hazard models were used to assess for an association between baseline hematologic variables and outcomes. Results: Of 1081 identified patients, 845 were included in the DFS/OS analysis. Median age was 61 (range 23-87), 70% male, 85% performance status (PS) 0-1. 31% and 67% had clinical stage II and III disease, respectively. 25% had elevated NLR (≥ 4), and 64% had elevated PLR (≥ 150). 98% of patients received FP-based nCRT, with 96% receiving ≥ 44 Gy (median 50 Gy [range 20-74]). 80% completed neoadjuvant chemotherapy and 94% completed neoadjuvant radiotherapy, with a pCR rate of 23%. After a median follow up time of 64 months, 6% developed local recurrence, 20% developed distant recurrence and 19% have died. 5-year OS and DFS were 78% (95% CI 74-81%) and 76% (95% CI 73-79%), respectively. In multivariate analyses, elevated baseline NLR and PLR were not prognostic for OS or DFS. Elevated NLR was a negative predictor of pCR (OR 0.61, p=0.037, 95% CI 0.38-0.97); there was no association with elevated PLR. Conclusions: Elevated NLR was a negative predictor of pCR, but not prognostic for DFS and OS. PLR was neither predictive nor prognostic.