Phase I study of primary treatment with 5-FU, oxaliplatin, irinotecan, levofolinate, and panitumumab combination chemotherapy in patients with advanced/recurrent colorectal cancer involving the wild-type RAS gene: the JACCRO CC-14 study

BACKGROUND: FOLFOXIRI is now regarded as the chemotherapy regimen that offers the best platform for the treatment of colorectal cancer. However, the safety and efficacy of FOLFOXIRI + panitumumab has not been demonstrated. We conducted a phase I study to determine the recommended dose of FOLFOXIRI + panitumumab as first-line treatment for RAS wild-type metastatic colorectal cancer (mCRC). METHODS: Patients received combination therapy consisting of panitumumab (6 mg/kg on day 1) + FOLFOXIRI [irinotecan (CPT-11), oxaliplatin (L-OHP) 85 mg/m(2), and folinate (LV) 200 mg/m(2)] on day 1, followed by fluorouracil (5-FU) 3200 mg/m(2) infused as a 46-h continuous infusion starting on day 1) repeated every 2 weeks as first-line treatment of RAS wild-type mCRC patients. A decrease in CPT-11 dose was planned (started at level 1: CPT-11 165 mg/m(2)). RESULTS: Seven patients were enrolled, and six were assessed for safety and efficacy. Maximum tolerated dose was not reached at level 1; all patients were treated at these levels. The common Grade 3 or 4 relevant toxicities were diarrhea (50%), hypokalemia (33%) and stomatitis (33%). No treatment-related deaths occurred. Of the six patients assessed four had partial response and the two others had stable disease; hence, the response rate was 66.7% (95% confidence interval 28.9–100%) and the disease control rate was 100%. Time to protocol treatment failure was 7.2 (1.4–7.3) months. CONCLUSION: The FOLFOXIRI + panitumumab chemotherapy regimen was well tolerated by our patients with mCRC and showed promising anti-tumor activity. The recommended phase II dose was determined to be the same as the standard doses of this regimen used worldwide.