Real-world Patterns of Adjuvant Chemotherapy Following Neoadjuvant Chemoradiation for Patients With Resected Rectal Adenocarcinoma.

Objective The objective of this study was to analyze patterns of adjuvant chemotherapy among patients with resected rectal adenocarcinomas following neoadjuvant chemoradiation and surgical resection. Methods Alberta Cancer Registry and other provincial electronic medical registries (2004 to 2018) identified patients with nonmetastatic rectal cancer who received neoadjuvant chemoradiation followed by surgical resection and either oxaliplatin-based or fluoropyrimidine-only adjuvant chemotherapy. Multivariable logistic regression analysis was then undertaken to identify factors associated with the use of either regimen. Kaplan-Meier survival estimates were used to compare overall survival between both groups and multivariable Cox regression analysis was then used to identify factors associated with worse overall survival. Results A total of 532 patients who fulfilled eligibility criteria were included in the current study: 347 patients received adjuvant fluoropyrimidine-only chemotherapy and 185 patients received adjuvant oxaliplatin-based chemotherapy. The following variables were associated with use of fluoropyrimidine-only adjuvant chemotherapy: older age (odds ratio [OR]: 1.04; 95% confidence interval [CI]: 1.02-1.06), higher Charlson comorbidity index (OR: 1.47; 95% CI: 1.00-2.15), and no involved lymph nodes in the surgical pathology (OR: 5.55; 95% CI: 3.66-8.41). Using Kaplan-Meier survival estimates, no difference in overall survival between patients treated with adjuvant oxaliplatin-based chemotherapy and those treated with adjuvant fluoropyrimidine-only chemotherapy was identified (P=0.152). Within multivariable Cox regression analysis, type of chemotherapy was not associated with a difference in overall survival (hazard ratio for fluoropyrimidine-only chemotherapy vs. oxaliplatin-based chemotherapy: 1.02; 95% CI: 0.61-1.71). Conclusion Oxaliplatin-based adjuvant chemotherapy is not associated with improved survival outcomes compared with fluoropyrimidine-only chemotherapy in this real-world study.