Staging Paradox and Discrepancy in Adjuvant Chemotherapy in Patients with T4N0, T1-2N1, and T3N1 Colon Cancer

BACKGROUND A survival paradox between T4N0 (stage IIB/C) and T3N1 (stage IIIB) colon cancer has been rarely reported. The indication and regimen of adjuvant chemotherapy are separately described in the guidelines. This study aimed to elucidate the prognostic factors and investigate proper adjuvant treatment in colon cancer patients at these stages. METHODS Patients who underwent R0 resection for pathological T4N0 (n = 49), T1-2N1 (n = 31), or T3N1 (n = 82) colon cancer between 2008 and 2016 at a single institute were retrospectively reviewed. The clinicopathological characteristics, status of adjuvant chemotherapy, and oncologic outcomes of patients with T4N0 tumors were compared with those of patients with T1-2N1 and T3N1 tumors. RESULTS The biological characteristics of T4N0 tumors were more aggressive compared with the characteristics of T1-2N1 tumors and were similar to those of T3N1 tumors. The usage rate of oxaliplatin as an adjuvant chemotherapy was significantly lower in T4N0 patients than in T1-2N1 and T3N1 patients. The rate of local recurrence was the highest in patients with T4N0 tumors, and the survival outcomes for patients with T4N0 tumors were significantly worse compared with those of T1-2N1 patients and were similar to those of T3N1 patients. A multivariate analysis revealed that lack of adequate use of oxaliplatin for adjuvant chemotherapy was the only prognostic factor. CONCLUSIONS T4N0 colon cancer had similar oncological characteristics and survival outcomes to T3N1 colon cancer. Systematic adjuvant chemotherapy, including oxaliplatin, should be incorporated into the therapy for T4N0 patients as well as T3N1 patients.