A phase II trial to evaluate the efficacy of panitumumab combined with fluorouracil-based chemotherapy for metastatic colorectal cancer: the PF trial.

PURPOSE: Fluorouracil monotherapy, instead of the FOLFOX or FOLFIRI regimen, is administered to patients intolerant to oxaliplatin or irinotecan because of their adverse effects. A prospective clinical trial was designed to evaluate the efficacy and safety of fluorouracil monotherapy combined with panitumumab administered to patients with KRAS wild-type (WT) metastatic colorectal cancer (mCRC) intolerant to oxaliplatin and irinotecan. Screening for potential serum biomarkers to predict early therapeutic responses was conducted. METHODS: This single-arm, open-label multicenter phase II trial recruited patients with KRAS WT mCRC from 16 institutes between January 2012 and October 2014. Panitumumab (6 mg/kg) was intravenously administered every 2 weeks, combined with fluorouracil monotherapy, in 2-week cycles. The primary objective was overall response rate, and secondary endpoints included disease-control rate, progression-free survival, overall survival, toxicity, and blood-test data. RESULTS: Forty patients (male, 65.0%; median age, 74 years; colon cancer, 72.5%) met eligibility criteria and received 7 cycles (median) of fluorouracil chemotherapy combined with panitumumab. There were no treatment-related deaths. Median time to treatment failure was 3.2 months. 23 (57.5%) patients experienced at least one adverse effect ≥ grade 3. The response rate was 10.0% (95% confidence interval 2.8-23.7%). Median progression-free survival and overall survival were 4.3 and 11.3 months, respectively. Total lactase dehydrogenase (LDH) levels and those of LDH-4 and LDH-5, quickly changed with disease reduction or progression. CONCLUSIONS: Fluorouracil monotherapy combined with panitumumab was safely administered to patients with KRAS WT mCRC intolerant to oxaliplatin and irinotecan. Serum LDH levels may predict early responses.