Revised Nodal Staging Integrating Tumor Deposit Counts With Positive Lymph Nodes in Patients With Stage III Colon Cancer

OBJECTIVE: We evaluated the prognostic value of tumor deposit (TD) counts and incorporated them with the number of positive lymph nodes to develop a revised nodal staging. SUMMARY BACKGROUND DATA: The current American Joint Committee on Cancer (AJCC) staging on colon cancer includes the TDs only for nodenegative patients, as N1c, and their counts are not considered. METHODS: We included consecutive patients with stage III colorectal cancer who underwent curative resections between January 2010 and December 2019. The patients were grouped as TD 0, TD 1, TD 2, or TD ≥3 based on their TD counts. Disease-free survival and overall survival were compared. RESULTS: Of 2446 eligible stage III patients, 658 (26.9%) had TDs. Among them, 500 (76.0%) patients concurrently had positive lymph nodes (LNs). TD counts were significantly related to worse disease-free survival (DFS) and overall survival regardless of pT stages or the number of positive LNs. The patients were restaged based on the integrated number of TD counts and positive LNs. The N3 stage, which had ≥10 integrated TDs and positive LNs, was newly classified. Among the patients who completed 6 months of adjuvant chemotherapy, those upstaged to N2 from an initial stage of N1 experienced significantly worse DFS than those confirmed as N1 in the revised N staging. The newly N3-staged patients showed significantly worse DFS than the patients initially staged as N2. CONCLUSIONS: Revised N staging using the integrated number of TD counts and positive LNs could predict DFS more accurately than current staging. It would also draw greater attention to the patients with high-risk stage III colon cancer staged as N3.