Immunotherapy in Stage III-IV Colon Cancer: A Propensity Score-Matched Analysis of the National Cancer Database

Immunotherapy for the systemic treatment of cancer offers new treatment possibilities for advanced malignancies. Despite promising initial results, evidence on efficacy of immunotherapy for colon cancer is lacking. Thus, we aimed to assess short-term and long-term outcomes of immunotherapy in patients with advanced colon cancer. A US National Cancer Database was searched for patients with stage III-IV colonic adenocarcinoma between 2010 and 2019. Propensity score matching was used to classify the cohort into 2 groups: patients who received immunotherapy and controls. Main outcome measures were primary outcome was overall survival (OS). A total of 23,778 patients with stage III-IV colonic adenocarcinoma were treated with immunotherapy during the study period compared to 114,753 controls. Immunotherapy treated patients were younger (median age 61 vs. 67 y; P <0.001), more often male (57.3% vs. 50.7%, P <0.001), had more private insurance (44.1% vs. 33.7%; P <0.001), had more left-sided tumors (49.5% vs. 39.1%; P <0.001) and liver metastasis (80.2% vs. 61.7%; P <0.001) than controls. Immunotherapy patients received more standard chemotherapy (49.8% vs. 41.6%; P <0.001). After propensity-score matching, mean OS was significantly shorter in the immunotherapy group compared with controls (34.7 vs. 36.2 mo; P =0.008). Cox regression analysis demonstrated that immunotherapy was associated with increased risk for mortality (HR: 1.1; 95% CI: 1.02-1.18; P =0.005). Patients who received immunotherapy had lower 90-day mortality rates compared with controls (2.3% vs. 3.6%; P =0.004), but the groups had equivalent 30-day mortality rates (0.7% vs. 0.8%; P =0.76). Immunotherapy showed no improvement in OS in patients with stage III-IV colon cancer.