Effect of neoadjuvant chemotherapy on overall survival in stage II and stage III colon cancer: A propensity-score matched analysis of the National Cancer Database

e15632 Background: Neoadjuvant chemotherapy (NAC) is currently indicated for patients with advanced colon cancer. However, there are little data regarding the impact of NAC on short-term outcomes and overall survival (OS). This study aimed to determine the role of NAC in patients with advanced colon cancer. Methods: A retrospective analysis of all patients with stage II-III colonic adenocarcinoma in the US National Cancer Database (NCDB) between 2006 and 2019. Propensity score matching was used to adjust for possible confounders. The cohort was divided into two equally matched groups: patients who received NAC and controls. The primary outcome was 5-year OS. Results: 902 (1.6% of the original cohort) patients with clinical stage II-III colonic adenocarcinoma were treated with NAC. Before matching, patients treated with NAC were significantly younger (61 vs 76 years; p < 0.001) and more often male (54.5% vs. 46.5%; p < 0.001) and had more private insurance (46.9% vs 22.6%; p < 0.001) and a lower Charlson comorbidity index score (p < 0.001). In addition, patients treated with NAC had more left-sided tumors (41.7% vs 30.1%; p < 0.001) and underwent more resections of a contiguous organ with colonic resection (27.1% vs 7.6%; p < 0.001). After matching, 620 patients were included in each group. The mean OS of patients in the NAC group was comparable to the control group (105.2 months, 95%CI: 98.1-112.2 vs 105 months, 95%CI: 98.2-111.7; p = 0.627). Stratifying OS based on clinical stage demonstrated that mean OS was significantly longer in patients with stage III (100.8 months, 95%CI 92.6-109.1 vs 88.4 months, 95%CI 79.7-97.1; p = 0.01), while the opposite effect was noted in stage II patients (106.1 months, 95%CI 96-116.3 vs 119.8 months, 95%CI 110.5-129.2; p = 0.04). Cox regression survival analysis showed that NAC was significantly associated with a lower risk of mortality (HR 0.72, 95%CI 0.64-0.8; p < 0.001). Conclusions: Preoperative neoadjuvant chemotherapy is associated with improved OS in patients with Stage III colon cancer, but not in patients with stage II disease.