Adjuvant chemotherapy does not improve cancer-specific survival for pathologic stage II/III rectal adenocarcinoma after neoadjuvant chemoradiotherapy and surgery: evidence based on long-term survival analysis from SEER data

Purpose Adjuvant chemotherapy is controversial in rectal cancer, especially after neoadjuvant chemoradiotherapy (NCRT). This retrospective study aims at evaluating adjuvant chemotherapy’s long-term survival benefits in stage II and stage III rectal adenocarcinoma (RC). Methods This study obtained data from the Surveillance, Epidemiology, and End Results (SEER) database registered between 2010 and 2015. The survival analyses used the Kaplan–Meier method and were compared by log-rank test. The factors that affect survival outcomes were analyzed by univariate and multivariate Cox regression. The propensity score matching (1:4) was used to ensure the balance of variables between different groups. Results The median follow-up time for overall patients was 64 months. The 5-year overall survival (OS) and cancer-specific survival (CSS) rates were 51.3% and 67.4% in the adjuvant chemotherapy (−) group and 73.9% and 79.6% in the adjuvant chemotherapy ( +) group ( p