Effect of Delay in Adjuvant Oxaliplatin-Based Chemotherapy for Stage III Colon Cancer

The belief that adjuvant chemotherapy (AC) for colon cancer must be commenced within 8 weeks is somewhat arbitrary. In our population-based study including 635 patients with stage III colon cancer, we analyzed the effect of delay in oxaliplatin-based AC beyond 8 weeks on recurrence-free survival (RFS) and cancer-specific survival (CSS). Administration of oxaliplatin-based AC beyond 8 weeks was not associated with inferior outcomes. Background: Less than 8 weeks has been recommended as the optimal time to initiate AC based on 2 meta-analyses that suggested worse survival with delayed AC. However, neither study included patients treated with an oxaliplatin-based chemotherapy. We aimed to investigate the effect of delay in initiating oxaliplatin-based chemotherapy on RFS and CSS for stage III colon cancer. Patients and Methods: Records of patients who initiated oxaliplatin-based AC for stage III colon cancer between 2006 and 2011 at the British Columbia Cancer Agency were retrospectively reviewed. Cox proportional models were used to analyze the effect of time to AC (TTAC) on RFS and CSS. TTAC was categorized into <= 8 weeks (G1) and > 8 weeks (G2). Results: Six hundred thirty-five patients were included (G1, n = 291; G2, n = 344). Median time from surgery to initiation of AC was 8.3 weeks. At a median follow-up of 57.9 months, 176 patients (27.7%) had disease recurrence and 118 (18.6%) had died. Five-year RFS was 70.9% (95% confidence interval [CI], 65.2-76.5) for G1 and 72.1% (95% CI, 67.2-77) for G2. Five-year CSS was 82% for G1 (95% CI, 87.09-76.91) and 82.8% for G2 (95% CI, 78.30-87.30). On multivariate analysis, delayed TTAC did not have prognostic significance on either RFS (hazard ratio [HR], 1.08; P = .609) or CSS (HR, 1.02; P = .893). Conclusion: In our population-based study, TTAC after stage III colon cancer resection did not have an effect on RFS or CSS. Contrary to most of the existing data, which are primarily based on 5-fluorouracil-based AC, delay of oxaliplatin-based AC beyond 8 weeks did not appear to be associated with inferior outcomes.