Adjuvant Chemotherapy Duration and Disease-Free Survival in Low-Risk Stage III Colon Cancer with N1a-b and N1c Disease: Insights from a Single-Center Retrospective Analysis.

Background: Tumor deposits (TDs) are known to have a poor prognosis independent of lymph node (LN) involvement and are considered equivalent to LN metastases in the latest staging system. In stage III colon cancer (CC), high-risk patients (pT4 or pN2) receive 6 months of adjuvant chemotherapy, while low-risk patients (pT1-3 and N1) are recommended either 3 or 6 months of CAPOX or 6 months of FOLFOX therapy. However, the optimal chemotherapy duration for low-risk patients classified as pN1c remains unknown. The aim of this study is to investigate the impact of adjuvant chemotherapy duration (3 months vs. 6 months) on survival in patients with low-risk stage III CC either in pN1a-b and pN1c patient groups.

Methods: We retrospectively analyzed patients with stage III CC who underwent surgery at a tertiary center between January 2014 and May 2024. Demographic and pathological data of patients were retrospectively collected. The primary outcome was disease-free survival (DFS).

Results: A total of 142 patients were included. Among the patients, 116 were pT1-3N1a-b and 26 were pT1-3N1c. Local (23.1% vs. 1.7%, P < 0.001) and overall (38.5% vs 14.6%, P = 0.011) recurrences were significantly higher in the pN1c group. Univariate and multivariate analyses revealed no significant impact of adjuvant chemotherapy duration on DFS in the pN1a-b group (P = 0.359), whereas in the pN1c group, 3-month chemotherapy resulted in significantly shorter DFS (P = 0.044) in univariate analysis.

Conclusion: Our study indicates that shorter duration of adjuvant chemotherapy is associated with worse survival and 6-month chemotherapy is recommended for patients with pT1-3 and N1c disease.