Survival benefit of adjuvant chemotherapy in stage II large (≥5 cm) colonic adenocarcinomas: A propensity-score matched analysis

Background

Current guidelines recommend selective adjuvant chemotherapy for stage II colon cancer with high-risk features. This study aimed to assess survival benefit of adjuvant chemotherapy in patients with stage II colon adenocarcinomas ≥5 cm without high-risk features.

Methods

The National Cancer Database was retrospectively reviewed (2010–2019) for all patients with pathologic stage II colonic adenocarcinomas ≥5 cm who underwent colectomy. Patients were divided into adjuvant and control groups that were propensity-score matched for baseline and treatment confounders. The primary outcome was 5-year overall survival (OS).

Results

Of 23,937 included patients, adjuvant chemotherapy was given to 2581 (10.8 %). Patient given adjuvant chemotherapy were younger, more often male, Black, had a Charlson score of 0 and private insurance, presented with left-sided cancers and microsatellite stable (MSS) tumors, and more frequently underwent segmental resections and open surgery. 796 patients in the adjuvant group were matched to 1592 patients in the control group. Adjuvant chemotherapy was associated with lower mortality (HR: 0.79; p = 0.022), however, it was not independently associated with improved OS when adjusted for other confounders (HR: 0.84; p = 0.157). The adjuvant group had significantly longer restricted mean OS than the control group (104.9 vs. 100.8 months; p = 0.007). The survival benefit was only noted in patients >50 years, female, White, with non-mucinous adenocarcinomas, MSS tumors, normal CEA levels, and had undergone open and emergency surgery.

Conclusions

The study did not demonstrate a clear survival benefit from adjuvant chemotherapy in patients with stage II adenocarcinoma ≥5 cm. A possible potential survival benefit was observed only in a subgroup of patients.