Effect of interval between neoadjuvant chemoradiotherapy and surgery on oncological outcomes in poor responders with locally advanced rectal cancer: a retrospective cohort study.

BACKGROUND: The optimal interval from completion of neoadjuvant chemoradiotherapy (CRT) to surgery in locally advanced rectal cancer remains controversial. It seems that delayed surgery is associated with an increase in pathological complete response rates. However, the prognostic effect of delayed surgery in poor responders is unclear. MATERIALS AND METHODS: Patients with locally advanced mid or distal rectal cancer undergoing neoadjuvant CRT followed by total mesorectal excision at a university teaching cancer center between June 2010 and December 2018 were retrospectively reviewed in this study. According to the tumor regression grade, poor responders (tumor regression grade 2-3) to neoadjuvant CRT were selected for analyses. Patients were divided into the longer interval group (greater than 8 weeks) and the shorter interval group (8 weeks or less) based on the wait time from completion of neoadjuvant CRT therapy to surgery. Results: among 916 eligible patients, 522 patients had a poor tumor response. There were 217 patients in the shorter interval group and 305 patients in the longer interval group. At the baseline, patients in the longer interval group were more likely to have a T3 stage and positive vascular invasion. Compared with patients in the shorter interval group, patients in the longer interval group had significantly worse overall survival and disease-free survival (DFS) (log-rank test, overall survival: P =0.004, DFS: P <0.001). The 3-year DFS rates were 75.6 and 63.1% in the shorter interval group and the longer interval group, respectively. In the multivariate analysis, delayed surgery was associated with an increased risk of mortality (hazard ratio: 2.003, 95% CI: 1.233-3.253, P =0.005) and recurrence (hazard ratio: 1.555, 95% CI: 1.121-2.156, P =0.008). CONCLUSION: Patients who had a poor tumor response should be identified by restaging MRI and receive radical surgery in time, without a prolonged interval.