PEAK: A Randomized, Multicenter Phase II Study of Panitumumab Plus Modified Fluorouracil, Leucovorin, and Oxaliplatin (mFOLFOX6) or Bevacizumab Plus mFOLFOX6 in Patients With Previously Untreated, Unresectable, Wild-Type KRAS Exon 2 Metastatic Colorectal Cancer

Abstract

Purpose To evaluate panitumumab plus modified fluorouracil, leucovorin, and oxaliplatin (mFOLFOX6) or bevacizumab plus mFOLFOX6 in patients with previously untreated wild-type (WT) KRAS exon 2 (codons 12 and 13) metastatic colorectal cancer (mCRC). A prespecified secondary objective was to assess treatment effects in an extended RAS analysis that included exons 2, 3, and 4 of KRAS and NRAS. Patients and Methods Patients with WT KRAS exon 2 tumors were randomly assigned at a one-to-one ratio to panitumumab plus mFOLFOX6 or bevacizumab plus mFOLFOX6. The primary end point was progression-free survival (PFS); secondary end points included overall survival (OS) and safety. Results Of 285 randomly assigned patients, 278 received treatment. In the WT KRAS exon 2 intent-to-treat group, PFS was similar between arms (hazard ratio [HR], 0.87; 95% CI, 0.65 to 1.17; P = .353). Median OS was 34.2 and 24.3 months in the panitumumab and bevacizumab arms, respectively (HR, 0.62; 95% CI, 0.44 to 0.89; P = .009). In the WT RAS subgroup (WT exons 2, 3, and 4 of KRAS and NRAS), PFS favored the panitumumab arm (HR, 0.65; 95% CI, 0.44 to 0.96; P = .029). Median OS was 41.3 and 28.9 months (HR, 0.63; 95% CI, 0.39 to 1.02; P = .058) in the panitumumab and bevacizumab arms, respectively. Treatment discontinuation rates because of adverse events were similar between arms. Conclusion PFS was similar and OS was improved with panitumumab relative to bevacizumab when combined with mFOLFOX6 in patients with WT KRAS exon 2 tumors. Patients with WT RAS tumors seemed to experience more clinical benefit with anti–epidermal growth factor receptor therapy.