Abstract
BACKGROUND: Colorectal cancer remains the second leading cause of cancer death in North America. Fluorouracil and oxaliplatin based adjuvant chemotherapy for resected colon cancer (CC) reduces cancer recurrence, but also causes significant toxicity requiring dose reductions. The effect of dose intensity on survival outcomes is not fully understood and strengthening the evidence supports informed decision making between patients and oncologists. METHODS: Patients treated with adjuvant chemotherapy, between 2006 and 2011, for resected colon cancer at four Canadian academic cancer centers were retrospectively analyzed. All patients must have received oxaliplatin with either capecitabine (CAPOX) or 5-FU (FOLFOX). Dose intensity (DI) was calculated as total delivered dose of an individual chemotherapy agent divided by the cumulative intended dose of that agent. The influence of DI on overall survival was examined. RESULTS: Five hundred thirty-one patients with high-risk stage II or stage III resected CC were eligible and included in the analysis. FOLFOX was the most common regimen (69.6%) with 29.7% of patients receiving CAPOX and 0.7% receiving both therapies. Median follow-up was 36.7 months. The median DI for 5-FU and capecitabine was 100% and 100% with 13.6% and 9.8% of patients receiving ≤ 80% DI, respectively. The median DI of oxaliplatin was 70% with 56.8% of patients receiving ≤ 80% DI. A DI of > 80% for each chemotherapy component was associated with a significant improvement in overall survival compared to those with a DI of ≤ 80% (5-FU HR = 0.23, 95% CI = 0.08-0.65, p = 0.006; capecitabine HR = 0.56, 95% CI = 0.33-0.94, p = 0.026; oxaliplatin HR = 0.52, 95% CI = 0.33-0.82, p = 0.005). Patients with T2 and/or N2 disease with an oxaliplatin DI > 80% had a trend towards improved survival (HR = 0.62, 95% CI = 0.38-1.02, p = 0.06). CONCLUSIONS: In resected CC an adjuvant chemotherapy DI of > 80%, of each chemotherapy agent, is associated with improved overall survival.