Comparative Effectiveness of 5-Fluorouracil with and without Oxaliplatin in the Treatment of Colorectal Cancer in Clinical Practice

Background: First-line chemotherapeutic treatment of colorectal cancer (CRC) typically comprises oral (capecitabine) or intravenous 5-fluorouracil (5-FU) plus leucovorin (LV), in combination with oxaliplatin (XELOX or FOLFOX, respectively), although debate exists regarding the best course of treatment by modality in clinical practice. Evidence from practice comparisons is important in considering the net benefit of alternative chemotherapy regimens, given expected differences in survival associated with compliance and age of patients treated in real life versus controlled trial settings. Patients and Methods: Practice variation in 5-FU treatment (i.e. 5-FU/leucovorin, FOLFOX, capecitabine and XELOX) of patients with CRC from an Australian area health service (n=636) was analyzed between modalities by patient age, tumour stage and site using non-parametric tests. Survival analyses (n=434) were conducted over a three-year follow-up period using Cox regression, adjusting for observed confounders. Results: FOLFOX was the most commonly administered regimen. 5-FU modality was significantly associated with patient age (p<0.001), tumour stage (p<0.001) and site (p<0.001). Cox regression analyses found no significant difference in survival with the addition of oxaliplatin to 5-FU regimens. Conclusion: Our findings suggested no survival benefit with the addition of oxaliplatin to 5-FU modalities in treating CRC in practice. This raises questions as to the net benefit of oxaliplatin, given its known toxicity profile and expense.