Oxaliplatin-based first-line chemotherapy is associated with improved overall survival compared to first-line treatment with irinotecan-based chemotherapy in patients with metastatic colorectal cancer - Results from a prospective cohort study

Purpose: Several randomized trials investigating the preferable first-line combination chemotherapy regimen for metastatic colorectal cancer have shown inconsistent findings. Because a substantial number of patients are still being treated with "chemo-only" first-line therapies without targeted agents, we compared overall survival (OS) of patients treated in routine practice with oxaliplatin-fluoropyrimidine and irinotecan-fluoropyrimidine. Patients and methods: Using the database of the Tumor Registry Colorectal Cancer, we identified 605 patients with metastatic colorectal cancer who received first-line fluoropyrimidine combination chemotherapy with either oxaliplatin (n= 430) or irinotecan (n= 175). The Tumor Registry Colorectal Cancer is a cohort study that prospectively documents treatment of colorectal cancer by office-based medical oncologists in Germany and has recruited over 5,000 patients. OS was estimated using the Kaplan-Meier method, and a multivariate Cox proportional hazard model was used to adjust for potentially confounding variables. Results: Median OS was 26.8 (95% confidence interval [CI] 22.4-31.9) months with an oxaliplatin-fluoropyrimidine combination and 18.3 (95% CI 15.1-23.2) months with irinotecan-fluoropyrimidine first-line "chemo-only" therapy. Median progression-free survival was 9.0 (8.1-10.2) and 7.9 (7.2-10.2) months, respectively. The difference in OS was confirmed if analysis was restricted to patients with synchronous metastases (no prior treatment). Among other variables, proportion of patients receiving any second-line therapy did not differ between groups. Oxaliplatin-based first-line therapy was associated with improved OS in multivariate analysis adjusted for potentially confounding variables (hazard ratio 0.678, 95% CI 0.510-0.901, P= 0.007). Conclusion: In clinical routine practice, first-line treatment with oxaliplatin-fluoropyrimidine combination chemotherapy compared to irinotecan-fluoropyrimidine combination is associated with improved survival in patients with metastatic colorectal cancer, independent of all examined potentially confounding factors.