Impact of adjuvant chemotherapy on long-term overall survival in patients with high-risk stage II colon cancer: a nationwide cohort study

Abstract

Background This study aimed to investigate the impact of adjuvant chemotherapy on long-term survival in unselected patients with high-risk stage II colon cancer including an analysis of each high-risk feature. Materials and Methods Data from the Danish Colorectal Cancer Group, the National Patient Registry and the Danish Pathology Registry from 2014 to 2018 were merged. Patients surviving > 90 days were included. High-risk features were defined as emergency presentation, including self-expanding metal stents (SEMS)/loop-ostomy as a bridge to resection, grade B or C anastomotic leakage, pT4 tumors, lymph node yield < 12 or signet cell carcinoma. Eligibility criteria for chemotherapy were age < 75 years, proficient MMR gene expression, and performance status ≤ 2. The primary outcome was 5-year overall survival. Secondary outcomes included the proportion of eligible patients allocated for adjuvant chemotherapy and the time to first administration. Results In total 939 of 3937 patients with stage II colon cancer had high-risk features, of whom 408 were eligible for chemotherapy. 201 (49.3%) patients received adjuvant chemotherapy, with a median time to first administration of 35 days after surgery. The crude 5-year overall survival was 84.9% in patients receiving adjuvant chemotherapy compared with 66.3% in patients not receiving chemotherapy, p < 0.001. This association corresponded to an absolute risk difference of 14%. Conclusion 5-year overall survival was significantly higher in patients with high-risk stage II colon cancer treated with adjuvant chemotherapy compared with no chemotherapy. Adjuvant treatment was given to less than half of the patients who were eligible for it.