Abstract
Neoadjuvant concurrent chemoradiation (CCRT) is standard treatment for clinical stage II/III rectal cancers. However, whether patients with pathological complete response (pT0N0, pCR) should receive adjuvant chemotherapy and whether delayed surgery will influence the pCR rate remains controversial. A nationwide population study was conducted using the Taiwan Cancer Registry Database from January 2007 to December 2013. Kaplan-Meier survival analysis was performed. Cox proportional hazards models were used to estimate multivariate adjusted hazard ratios (HR) and 95% confidence intervals (95% CI). Of the 1,914 patients who received neoadjuvant CCRT, 259 (13.6%) achieved pCR and had better survival (adjusted HR: 0.37, 95% CI: 0.24-0.58; p < 0.001). The cumulative rate of pCR rose up to 83.4% in the 9th week and slowly reached a plateau after the 11th week. Among the patients with pCR, those who received adjuvant chemotherapy had no survival benefits compared to those without adjuvant chemotherapy (adjusted HR: 0.72, 95 CI: 0.27-1.93; p = 0.52). By subgroup analysis, those younger than 70-year old and received adjuvant chemotherapy had better survival benefit than those without adjuvant chemotherapy (adjusted HR: 0.19, 95% CI: 0.04-0.97; p = 0.046). Delayed surgery by 9-12 weeks after the end of neoadjuvant CCRT can maximize the pCR rate, which is correlated with better survival. Adjuvant chemotherapy may be considered in patients with pCR and aged <70-year old, but further prospectively randomized controlled trials are warranted to validate these findings.