Background: Fluoropyrimidine and oxaliplatin doublets are the standard of care for adjuvant treatment of resected stage III colon cancer. Their efficacy is presumed to be similar based on pooled analysis of trial data, but they have never been directly compared in randomised trials.
Aims: To compare real-world data on survival outcomes, dose intensity and tolerability of fluoropyrimidine and oxaliplatin doublet regimens used in post-operative treatment of stage III colon cancer.
Methods: We retrospectively reviewed electronic charts of all patients (n=257) treated with 5-fluorouracil, leucovorin and oxaliplatin (FOLFOX) or capecitabine and oxaliplatin (CAPOX) in the adjuvant setting for stage III colon cancer across four institutions between 2006-2016. The relative dose intensity (RDI) of fluoropyrimidine and oxaliplatin of each regimen was defined by the ratio of the delivered dose to the standard dose over the planned 6 months of treatment.
Results: Patients who received FOLFOX (n=195) or CAPOX (n=62) had evenly matched patient and tumour characteristics. More patients were able to tolerate >90% of the intended fluoropyrimidine and oxaliplatin in FOLFOX group (46.7% and 25.1% respectively) than in CAPOX group (21.0% and 14.5% respectively). The mean RDI for fluoropyrimidine (85% vs 78%, p=0.006) and oxaliplatin (72% vs 66%, p=0.063) was higher with FOLFOX compared to CAPOX. There was significantly improved disease-free survival with CAPOX over FOLFOX (HR 0.47, 95%CI 0.22-0.99, p=0.048), with this difference being most pronounced in the high-risk (T4 or N2) group. No difference in overall survival was observed between the two groups (HR 0.53, 95%CI 0.20-1.43, p=0.210). Patients receiving CAPOX had more grade ≥2 diarrhoea (p=0.016) and hand-foot syndrome (p<0.001) but not peripheral neuropathy, myelosuppression or fatigue.
Conclusions: In a real-world setting, despite less chemotherapy being administered in those receiving CAPOX, they had better DFS when compared to FOLFOX in the adjuvant setting.