Laparoscopic versus open surgery for locally advanced rectal cancer following neoadjuvant chemoradiotherapy with S-1: Short- and long-term outcomes of multicenter prospective phase II trials

793 Background: We have reported the effectiveness of neoadjuvant radiotherapy (RT) combined with S-1 in terms of compliance and pathologic response for locally advanced rectal cancer. In the present study, we aimed to evaluate the safety and efficacy of laparoscopic surgery for locally advanced rectal cancer following neoadjuvant RT combined with S-1 in comparison with open surgery. Methods: Two multicenter prospective phase II trials were conducted (UMIN003396, UMIN003398). A total of 63 patients with locally advanced rectal cancer classified as T3-4, N0-3, and M0 were enrolled, and neoadjuvant RT combined with S-1 and total mesorectal excision with D3 lymphadenectomy was performed. Of these, 57 patients were analyzed and divided into a laparoscopic group (LAP, n = 43) and open group (OP, n = 14). We evaluated the short- and long-term outcomes of laparoscopic surgery compared with open surgery by univariate and multivariate analyses. Results: In the patient background, there were no significant differences between the two groups except that cases with T3 and N0 were significantly higher in the LAP compared with the OP. In the operative findings, operation time was longer (mean 447 min vs. 352 min, p = 0.007) and blood loss was lesser (median 220 ml vs. 485 ml, p = 0.033) in the LAP than those in the OP. Although there were no significant differences observed in the incidence of perioperative and late complications between the two groups, reoperation within 30 days was significantly less in the LAP compared with the OP (1 case vs. 5 cases, p = 0.0004). In the multivariate analysis, a distance of the tumor from anal verge within 3 cm was the independent risk factor for reoperation within 30 days. Furthermore, estimated 5-year disease-free survival (LAP 72 % vs. OP 73 %, p = 0.945) and 5-year overall survival (LAP 76 % vs. 75 %, p = 0.836) didn’t significantly differ between the two groups in the Kaplan–Meier curve. Conclusions: The findings of this study demonstrated that laparoscopic surgery for locally advanced rectal cancer following neoadjuvant RT combined with S-1 could be an optional procedure in terms of short- and long-term outcomes. Clinical trial information: UMIN000003396, UMIN000003398.