Delay in Adjuvant Chemotherapy and Survival Advantage in Stage III Colon Cancer.

Background: Adjuvant chemotherapy after resection is the standard of care for stage III colon cancer, yet many patients omit chemotherapy. We aimed to describe the impact of delayed chemotherapy on overall survival across multiple time points.

Study Design: The 2006 to 2014 National Cancer Data Base (NCDB) was queried for patients with single primary stage III adenocarcinoma of the colon. Patients were grouped by receipt and timing of chemotherapy from resection date: chemotherapy omitted, <6 weeks, 6 to 8 weeks, 8 to 12 weeks, 12 to 24 weeks, and >24 weeks. Subgroup analyses were performed for those with comorbidities and those who had postoperative complications. Overall survival was compared using Cox proportional hazard modeling, adjusting for patient, tumor, and facility characteristics.

Results: In total, 72,057 patients were included; 20,807 omitted chemotherapy, 22,705 received it at <6 weeks, 15,412 between 6 and 8 weeks, 9,049 between 8 and 12 weeks, 3,595 between 12 and 24 weeks, and 489 at >24 weeks after resection. Compared with patients who omitted chemotherapy, patients who received chemotherapy at <6 weeks (hazard ratio [HR] 0.44), 6 to 8 weeks (HR 0.45), 8 to 12 weeks (HR 0.52), 12 to 24 weeks (HR 0.61), and >24 weeks (HR 0.68) had superior overall survival (p < 0.001). This survival benefit was preserved across subgroups (p < 0.001).

Conclusions: After resection of stage III colon cancer, patients should receive adjuvant chemotherapy within 6 to 8 weeks for maximal benefit. However, chemotherapy should be offered to patients who are outside the optimal window, who have significant comorbidities, or who have had a complication more than 24 weeks from resection to improve the overall survival compared with omitting chemotherapy.