A prospective, single-arm, multicenter trial of neoadjuvant chemotherapy with mFOLFOX6 plus panitumumab without radiotherapy for locally advanced rectal cancer

Purpose The present study evaluated the safety and efficacy of neoadjuvant chemotherapy with modified 5-fluorouracil, leucovorin, and oxaliplatin (mFOLFOX6) plus panitumumab in clinical stage III rectal cancer with KRAS wild-type. Methods We conducted a prospective multicenter phase II trial. KRAS wild-type clinical stage III rectal cancer patients were enrolled. Patients received 6 cycles of mFOLFOX6 with 6 mg/kg panitumumab as neoadjuvant chemotherapy. The primary outcome was the response rate (RR) defined by RECIST. Lateral lymph node dissection (LLDN) was performed when patients had a locally advanced tumor < 9 cm from the anal margin. Results A total of 50 patients were enrolled. Twelve (24.0%) experienced grade 3-4 adverse events during neoadjuvant chemotherapy. The RR was 88.0% (complete response 2.0%, partial response 86.0%), which met the primary outcome. All patients underwent laparoscopic surgery and achieved R0 resection. Seven patients underwent resection of other adjacent organs, and 43 underwent LLND. Twelve patients (24.0%) experienced grade 3-4 postoperative complications, and 4 (8.0%) had pathological complete response (pCR). Thirteen patients (26.0%) had lymph node metastasis. Forty-five patients (90.0%) received postoperative adjuvant chemotherapy. The 3-year relapse-free survival (RFS) and overall survival (OS) rates were 79.0% and 93.7%, respectively. Conclusions Neoadjuvant chemotherapy of mFOLFOX6 plus panitumumab without radiotherapy resulted in a low pCR rate but a high PR rate, low local recurrence rate, and good long-term outcome, suggesting that this treatment strategy may be a viable option for patients unable or unwilling to receive radiotherapy. The trial was registered with the UMIN Clinical Trials Registry, number 000006039.