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.