Patterns of recurrence in patients with curative resected rectal cancer according to different chemoradiotherapy strategies: Does preoperative chemoradiotherapy lower the risk of peritoneal recurrence?

The present study aimed to compare the pattern of distant recurrence between patients with non-metastatic rectal cancer treated with pre-operative (OP) and those treated with post-operative (post-OP) chemoradiotherapy (CRT). A total of 631 patients with newly diagnosed non-metastatic rectal cancer who had received pre-OP or post-OP CRT with curative intent surgery between August 2008 and April 2015 were identified. Inverse probability of treatment weighting (IPTW) was performed to account for baseline differences between the two arms. Overall, 449 and 182 patients were treated with pre-OP and post-OP CRT, respectively. Sex, tumor location, clinical tumor stage, CRT regimen and adjuvant chemotherapy regimen were significantly different between the two arms. The median follow-up duration was 55.4 months (range, 53.7-57.1). The 5-year distant recurrence-free survival (RFS) rates and 5-year overall survival (OS) rates were not significantly different between the pre-OP and post-OP CRT arms (RFS, 67.5 vs. 71.6%, P=0.595 and OS, 81.9 vs. 77.0%, P=0.449), and no difference was observed in the distant recurrence patterns. Following IPTW, there was still no difference in distant RFS (pre-OP vs. post-OP CRT; hazard ratio (HR)=0.62; P=0.911), but pre-OP CRT was significantly associated with lower peritoneal recurrence (pre-OP vs. post-OP CRT; HR, 0.13; P=0.032). In addition, there was no significant difference in OS between the two arms (pre-OP vs. post-OP CRT; HR, 0.85; P=0.665). In conclusion, although distant RFS was not significantly different between the two arms, pre-OP CRT was significantly associated with a lower risk of peritoneal recurrence than post-OP CRT in patients non-metastatic rectal cancer. [ABSTRACT FROM AUTHOR]