Abstract

BackgroundThe Panitumumab Randomized trial In combination with chemotherapy for Metastatic colorectal cancer to determine Efficacy (PRIME) demonstrated that panitumumab–FOLFOX4 significantly improved progression-free survival (PFS) versus FOLFOX4 as first-line treatment of wild-type (WT) KRAS metastatic colorectal cancer (mCRC), the primary end point of the study.Patients and methodsPatients were randomized 1:1 to panitumumab 6.0 mg/kg every 2 weeks + FOLFOX4 (arm 1) or FOLFOX4 (arm 2). This prespecified final descriptive analysis of efficacy and safety was planned for 30 months after the last patient was enrolled.ResultsA total of 1183 patients were randomized. Median PFS for WT KRAS mCRC was 10.0 months [95% confidence interval (CI) 9.3–11.4 months] for arm 1 and 8.6 months (95% CI 7.5–9.5 months) for arm 2; hazard ratio (HR) = 0.80; 95% CI 0.67–0.95; P = 0.01. Median overall survival (OS) for WT KRAS mCRC was 23.9 months (95% CI 20.3–27.7 months) for arm 1 and 19.7 months (95% CI 17.6–22.7 months) for arm 2; HR = 0.88; 95% CI 0.73–1.06; P = 0.17 (68% OS events). An exploratory analysis of updated survival (>80% OS events) was carried out which demonstrated improvement in OS; HR = 0.83; 95% CI 0.70–0.98; P = 0.03 for WT KRAS mCRC. The adverse event profile was consistent with the primary analysis.ConclusionsIn WT KRAS mCRC, PFS was improved, objective response was higher, and there was a trend toward improved OS with panitumumab–FOLFOX4, with significant improvement in OS observed in an updated analysis of survival in patients with WT KRAS mCRC treated with panitumumab + FOLFOX4 versus FOLFOX4 alone (P = 0.03). These data support a positive benefit-risk profile for panitumumab–FOLFOX4 for patients with previously untreated WT KRAS mCRC. KRAS testing is critical to select appropriate patients for treatment with panitumumab.