Impact of adjuvant chemotherapy on survival after pathological complete response in rectal cancer: a meta-analysis of 31,558 patients

Locally advanced rectal cancer (LARC) typically involves neoadjuvant chemoradiotherapy (nCRT) followed by surgery (total mesorectal excision, TME). While achieving a complete pathological response (pCR) is a strong indicator of a positive prognosis, the specific benefits of adjuvant chemotherapy after pCR remain unclear. To address this knowledge gap, we conducted a systematic review and meta-analysis to assess the potential advantages of adjuvant therapy in patients who achieve pCR.

In this study, we searched Medline, Embase, and Web of Science databases for relevant research. We focused on binary outcomes, analyzing them using odds ratios (ORs) with 95% confidence intervals (CIs). To account for potential variability between studies, all endpoints were analyzed with DerSimonian and Laird random-effects models. We assessed heterogeneity using the I² statistic and employed the R statistical software (version 4.2.3) for all analyses.

Thirty-four studies, comprising 31,558 patients, were included. The outcomes demonstrated a significant difference favoring the AC group in terms of overall survival (OS) (HR 0.75; 95% CI 0.60–0.94; p = 0.015; I² = 0%), and OS in 5 years (OR 1.65; 95% CI 1.21–2.24; p = 0.001; I² = 39%). There was no significant difference between the groups for disease-free survival (DFS) (HR 0.94; 95% CI 0.76–1.17; p = 0.61; I² = 17%), DFS in 5 years (OR 1.19; 95% CI 0.82–1.74; p = 0.36; I² = 43%), recurrence-free survival (RFS) (HR 1.10; 95% CI 0.87–1.40; p = 0.39; I² = 0%), and relapse-free survival (OR 1.08; 95% CI 0.78–1.51; p = 0.62; I² = 0%).

This systematic review and meta-analysis found a significant difference in favor of the ACT group in terms of survival after pCR. Therefore, the administration of this treatment as adjuvant therapy should be encouraged in clinical practice.