Patients with tumor deposits benefit equally from adjuvant therapy compared to other stage III colon cancer groups: two retrospective population-based studies

BACKGROUND: Tumor deposits (TD) are independent poor prognostic indicators of an increased risk of distant metastasis. In TNM classification, they are included in the N1c subcategory in the absence of lymph node metastasis (LNM). However, there is still limited knowledge regarding the relative effects of systemic treatment in colon cancer (CC) patients with TD. MATERIAL-METHOD: We conducted a retrospective population-based analysis of over 50,000 stage III CC patients from the Dutch and SEER cohorts. Patients were subdivided into groups based on the presence of TD, LNM, or both, and whether or not they received systemic treatment. Relative treatment effects were assessed by calculating the hazard ratios (HR) for 5-year overall survival (OS) in each group. RESULTS: In the Dutch cohort of 13,704 patients, systemic treatment resulted in a constant better 5-year OS with HR 3.5 (%95 CI 3.2–3.7) for the LNM group, 4.6 (95% CI 3.2–6.8) for the TD group, and 3.5 (95% CI 3.2–4.0) for the LNM + TD group (all p < .001). A similar effect of treatment was seen in the SEER cohort of 43,148 patients, where HR for the LNM, TD, and LNM + TD groups were 3.0 (95% CI 2.9–3.1), 3.2 (95% CI 2.8–3.7), and 3.0 (95% CI 2.8–3.1), respectively (all p < .001). CONCLUSIONS: Relative effect of treatment was consistent across all three groups in both cohorts which suggest patients with TD benefit from treatment similarly to other groups. Our results highlight the importance of classifying patients with TD as stage III, even in the absence of LNM.