A Japanese multicenter phase II study of adjuvant chemotherapy with mFOLFOX6/CAPOX for stage III colon cancer treatment after D2/D3 lymphadenectomy.

Purpose: A phase II trial was conducted to investigate the benefit of oxaliplatin-based adjuvant chemotherapy in Japanese stage III colon cancer patients.

Methods: Eligible patients were scheduled to receive 12 cycles of mFOLFOX6 or 8 cycles of CAPOX in adjuvant settings. The primary endpoint was the 3-year disease-free survival (DFS). Cox proportional hazards regression was performed to identify risk factors for a worse DFS.

Results: A total of 130 patients, including 73 patients receiving mFOLFOX6 and 57 patients receiving CAPOX, were enrolled from 16 institutions between April 2010 and April 2014. The 3-year DFS was 82.2%, exceeding the expected primary endpoint of 81.7%. The 3-year DFS tended to be higher in patients receiving mFOLOFOX6 than in those receiving CAPOX (mFOLFOX6, 86.3%; CAPOX, 76.9%; P = 0.06). The 3-year DFS rates did not differ markedly based on the risk stratification (T1/T2/T3 N1 vs. T4 or N2) indicated by the IDEA COLLABORATION study (P = 0.22). In the multivariate analysis, stage IIIC (P = 0.046) and early discontinuation (P < 0.01) were identified as independent significant risk factors for a worse DFS.

Conclusion: Our findings represent the first positive results in a Japanese phase II trial of adjuvant chemotherapy with mFOLFOX6/CAPOX. Early discontinuation within 2 months was an independent risk factor for a shorter DFS.