Adjuvant chemotherapy after preoperative (chemo) radiotherapy and surgery for patients with rectal cancer: a systematic review and meta-analysis of individual patient data

Background The role of adjuvant chemotherapy for patients with rectal cancer after preoperative (chemo) radiotherapy and surgery is uncertain. We did a meta-analysis of individual patient data to compare adjuvant chemotherapy with observation for patients with rectal cancer. Methods We searched PubMed, Medline, Embase, Web of Science, the Cochrane Library, CENTRAL, and conference abstracts to identify European randomised, controlled, phase 3 trials comparing observation with adjuvant chemotherapy after preoperative (chemo) radiotherapy and surgery for patients with non-metastatic rectal cancer. The primary endpoint of interest was overall survival. Findings We analysed data from four eligible trials, including data from 1196 patients with (y)pTNM stage II or III disease, who had an R0 resection, had a low anterior resection or an abdominoperineal resection, and had a tumour located within 15 cm of the anal verge. We found no significant differences in overall survival between patients who received adjuvant chemotherapy and those who underwent observation (hazard ratio [HR] 0.97, 95% CI 0.81-1.17; p=0.775); there were no signifi cant differences in overall survival in subgroup analyses. Overall, adjuvant chemotherapy did not significantly improve disease-free survival (HR 0.91, 95% CI 0.77-1.07; p=0.230) or distant recurrences (0.94, 0.78-1.14; p=0.523) compared with observation. However, in subgroup analyses, patients with a tumour 10-15 cm from the anal verge had improved disease-free survival (0.59, 0.40-0.85; p=0.005, p(interaction) = 0.107) and fewer distant recurrences (0.61, 0.40-0.94; p=0.025, p(interaction) = 0.126) when treated with adjuvant chemotherapy compared with patients undergoing observation. Interpretation Overall, adjuvant fluorouracil-based chemotherapy did not improve overall survival, disease-free survival, or distant recurrences. However, adjuvant chemotherapy might benefit patients with a tumour 10-15 cm from the anal verge in terms of disease-free survival and distant recurrence. Further studies of preoperative and postoperative treatment for this subgroup of patients are warranted.