Impact of time to surgery in locally advanced rectal cancer patients.

719 Background: Patients with locally advanced rectal cancer (LARC) undergo surgery at 6-8 weeks after neoadjuvant chemoradiation based on standard protocol. However, the optimal time to undergo surgery remains debatable. The goal of this study was to identify associations between time to surgery and additional variables with overall survival (OS) and recurrence rates in LARC patients. Methods: A retrospective chart review was conducted for 80 LARC patients with T3 or node positive disease, who have undergone neoadjuvant chemoradiation and surgery at St. Michael’s Hospital from January 1st 2005-December 31st 2015. Patients were divided into 4 groups based on time to surgery: 4-6 weeks (group 1), 6-8 weeks (group 2), 8-10 weeks (group 3), and > 10 weeks (group 4). Cox proportional hazards model was used to find associations with recurrence and OS. Results: Of the 80 patients, 67.5% (n = 54) were male and 32.5% (n = 26) were female. Median age at diagnosis was 59 years (range, 28-80 years). Median follow-up was 4.84 years. Recurrence occurred in 29% (n = 23) of patients. Incidence of death was 11% (n = 9). Pathologic complete response (pCR) was achieved in 15% (n = 12) of patients. Statin use during chemoradiation was prevalent in 25% (n = 20) of patients. Compared to group 1, patients in group 2 had a 14% reduction in the risk of recurrence (hazard ratio (HR): 0.86, 95% CI: 0.252.91); group 3 had a 69% reduction (HR: 0.31, 95% CI: 0.081.22) and group 4 had a 55% reduction (HR: 0.45, 95% CI: 0.073.08). There was no statistically significant difference in OS between the 4 groups. Furthermore, patients who took statins during chemoradiation had improved OS (HR: 5.42, 95% CI: 39.27.48, p < 0.019) with no difference in pCR rate. Conclusions: This study shows that surgery at 8-10 weeks after chemoradiation offers the best disease-free survival outcome. It also highlights a mortality benefit conferred by statin use during chemoradiation. This could be attributed to the radiosensitizing effects of statins, which allow tumor stem cells to undergo enhanced autophagy. Further prospective studies are warranted to investigate this therapeutic benefit.