Trends in the treatment of stage IIB/C and IIIA colorectal cancer: A National Cancer Database (NCDB) analysis.

e15658 Background: The standard treatment for early-stage colon cancer (CC) involves upfront surgical resection of the primary tumor and regional lymph nodes, followed by adjuvant chemotherapy (CT) in selected patients. The benefit of adjuvant CT in stage II CC is controversial, with decisions guided by clinicopathologic risk factors. For stage III CC, fluoropyrimidine (FP)-based CT with or without oxaliplatin is recommended, with regimen duration (3 vs. 6 months) tailored to clinicopathologic features. Although stage IIIA generally has a better prognosis than IIC, trials supporting oxaliplatin-based CT included both stages. This study aimed to compare outcomes of stage IIIA patients treated with surgery alone or with adjuvant CT and assess the impact of nodal dissection extent and age. Differences between stages IIB/C and IIIA were also explored. Methods: Using the National Cancer Database (NCDB), we identified adults aged ≥18 with stage IIB, IIC, and IIIA colon adenocarcinoma diagnosed between 2010-2020 who underwent surgery. Baseline characteristics were compared using Fisher’s exact and Mann-Whitney U tests. Kaplan-Meier analysis estimated 3- and 5-year survival, with log-rank tests for comparisons. Cox proportional hazards models assessed overall survival and prognostic factors. Results: The study included 5870 stage IIB, 3046 stage IIC, and 5195 stage IIIA CC patients, with median diagnosis ages of 71, 69, and 66, respectively. Adjuvant CT was given to 37%, 46.6%, and 74% of stage IIB, IIC, and IIIA patients, respectively. Among pts with stage IIB, 802 (37%) patients received FP only and 1291 (60%) patients received FP and oxaliplatin. Among patients with stage IIC, 415 (29%) patients received FP monotherapy and 964 (68%) pts received FP and oxaliplatin. Among patients with stage IIIA, 780 (20%) patients received FP single agent and 2918 (76%) pts received FP combination with oxaliplatin. Stage IIIA showed superior 3-year overall survival (3yOS) compared to IIB and IIC (85.6%, 71%, and 72.4%, p < 0.001). Oxaliplatin addition improved 3yOS in stage IIIA (92.9% vs. 84.3%, p < 0.001) but not in stages IIB (p = 0.8) or IIC (p = 0.6). In stage IIIA, T1N2A patients did not benefit from adjuvant CT (3yOS: 87.4% vs. 75%, p = 0.3) on univariate analysis and multivariate analysis (HR: 1.21, 95% CI 0.5 – 2.9, p = 0.4), while T1-2N1 patients showed improved 3yOS (96.7% vs. 73.5%, p < 0.001). Lymphadenectomy extent impacted survival; CT improved outcomes across < 12, 12-20, and > 20 lymph nodes examined (p < 0.001). Adjuvant CT benefits were consistent across age groups ( < 70: 3yOS of 93.2% vs. 77.6%, p < 0.001; ≥70: 3yOS of 85% vs. 63.3%, p < 0.001). Conclusions: Adjuvant CT benefits stages IIB, IIC, and IIIA, but oxaliplatin adds survival benefits only in stage IIIA. Notably, T1N2A patients did not benefit from adjuvant CT, highlighting the need to to rediscuss pathological staging in CC given different impact of T and N stages in prognosis.