Adjuvant chemotherapy in colon cancer: what is the evidence?

Over the last 12 years, numerous randomized trials have addressed the role of adjuvant chemotherapy in resected colon cancer. Together, these studies give conclusive evidence of the benefit of adjuvant 5-fluorouracil combined with folinic acid in stage III (node positive) disease and this is now considered the standard of care. The chemotherapy appears to be equally effective whether it is given daily for 5 days per month or on a weekly schedule. The overall effect is a relative reduction in tumour -recurrence of 25% or an absolute improvement in survival of 10%. However, doubt remains as to the role of adjuvant chemotherapy in stage II colon cancer. To date, most of the randomized trials have demonstrated a relative reduction in tumour recurrence but have not shown any significant impact on survival. It seems likely that this inability to demonstrate a survival benefit from adjuvant chemotherapy in stage II disease relates to the fact that the trials have been underpowered to do so. Nevertheless, the absolute survival advantage is only about 2% and clinicians need to weigh this against the costs and toxicities of the treatment when managing these patients.