Real-world tolerance and outcomes of oxaliplatin-based adjuvant chemotherapy for stage III colon cancer : does dose intensity matter?

Introduction: Fluoropyrimidine and oxaliplatin-based adjuvant chemotherapy delivered as 5-fluorouracil, leucovorin and oxaliplatin (FOLFOX), or capecitabine and oxaliplatin (CAPOX) is the standard of care for resected stage III colon cancer. Without randomized trial data, we compared real-world dose intensity, survival outcomes, and tolerability of these regimens. Methods: Records of patients treated with FOLFOX or CAPOX in the adjuvant setting for stage III colon cancer across four institutions in Sydney during 2006–2016 were reviewed. The relative dose intensity (RDI) of fluoropyrimidine and oxaliplatin of each regimen, disease-free survival (DFS), overall survival (OS), and incidence of grade ≥2 toxicities were compared. Results: Characteristics of patients receiving FOLFOX (n = 195) and CAPOX (n = 62) were evenly matched. FOLFOX patients had a higher mean RDI for both fluoropyrimidine (85% vs. 78%, p < 0.01) and oxaliplatin (72% vs. 66%, p = 0.06). In spite of a lower RDI, CAPOX patients trended toward a better 5-year DFS (84% vs. 78%, HR = 0.53, p = 0.068) and similar OS (89% vs. 89%, HR = 0.53, p = 0.21) compared to the FOLFOX group. This difference was most pronounced in the high-risk (T4 or N2) group where 5-year DFS was 78% versus 67% (HR = 0.41, p = 0.042). Patients receiving CAPOX experienced more grade ≥2 diarrhea (p = 0.017) and hand-foot syndrome (p < 0.001) but not peripheral neuropathy or myelosuppression. Conclusion: In a real-world setting, patients who received CAPOX had similar OS rates when compared to those receiving FOLFOX in the adjuvant setting in spite of lower RDI. In the high-risk population, CAPOX appears to demonstrate a superior 5-year DFS over FOLFOX.