Determining the survival benefit of postoperative radiotherapy in patients with pT1-3N1M0 rectal cancer undergoing total mesorectal excision: a retrospective analysis.

BACKGROUND: The National Comprehensive Cancer Network guidelines recommend routine postoperative adjuvant radiotherapy and chemotherapy for patients with stage III rectal cancer who do not receive neoadjuvant therapy before surgery. The present study aimed to evaluate the value of postoperative radiotherapy in patients with low-risk disease (pT1-3N1M0) who did not receive neoadjuvant therapy prior to total mesorectal excision.

METHODS: We used the Surveillance, Epidemiology, and End Results database (2004-2016) to retrospectively recruit patients with pT1-3N1M0 rectal cancer whose initial treatment was radical surgery with postoperative adjuvant chemotherapy. A propensity score model was used to balance the baseline covariates.

RESULTS: Of the 2012 patients included in the present study, 1384 received adjuvant chemoradiotherapy (radio group), whereas the remaining 718 received chemotherapy alone (no-radio group). There was no significant difference in cancer-specific survival rate between the two groups (log-rank test χ2  = 2.372, P = 0.124) in the overall sample. Additionally, in the propensity score-matched cohort, adjuvant radiotherapy did not improve cancer-specific survival. Subgroup analysis showed that having three positive lymph nodes and a tumor > 50 mm, combined with postoperative adjuvant chemotherapy, could lead to an improved tumor-specific survival rate, while other cases did not benefit from postoperative radiotherapy.

CONCLUSIONS: For patients with pT1-3N1M0 rectal cancer who did not receive neoadjuvant therapy before surgery, postoperative radiotherapy in addition to adjuvant chemotherapy did not significantly improve survival rates. The number of positive nodes (n = 3) and tumor size (> 50 mm) were found to be potential screening indicators for postoperative adjuvant radiotherapy.