A Prospective, Single-arm, Multicenter Trial of Diverting Stoma Followed by Neoadjuvant Chemotherapy Using mFOLFOX6 for Obstructive Colon Cancer YCOG 1305 (PROBE Study)

Objective: We conducted the first prospective clinical trial of neoadjuvant chemotherapy for patients with obstructive colon cancer. Background: Obstructive colorectal cancer is locally advanced colorectal cancer with a poor prognosis. The effect of neoadjuvant chemotherapy for obstructive colon cancer is unclear. Methods: We conducted a single arm, multicenter trial involving patients from the Yokohama Clinical Oncology Group with obstructive colon cancer. All eligible patients underwent diverting stoma formation before neoadjuvant chemotherapy. Patient received 6 cycles of mFOLFOX6 followed by primary tumor surgery and then 6 cycles of adjuvant chemotherapy. The primary endpoint was the objective response rate of all intended neoadjuvant therapy. The study was registered with the Japanese Clinical Trials Registry as UMIN000013198. Results: Between April 2014, and July 2016, 50 patients were registered, and 46 received neoadjuvant chemotherapy. The objective response rate as the primary endpoint was 67.4%. The most common grade >3 adverse event associated with neoadjuvant chemotherapy was neutropenia (28.3%). Fortyfive patients underwent surgical resection of the primary lesion (R0 resection in all cases). Grade >2 surgery-related complications occurred in 7 patients (15.6%). The downstaging rate was 48.9%, and the moderate or greater regression rate was 52.2%; no cases showed pathological complete response. Adjuvant chemotherapy with mFOLFOX6 was performed in 34 patients (75.6%). The 3-year relapse-free and overall survival rates were 76.5% and 95.4%, respectively. Conclusion: Neoadjuvant chemotherapy using mFOLFOX6 was feasible and might be a treatment option for patients with obstructive colon cancer. Further large-scale studies are warranted to confirm the present findings.