Background: PEAK estimated the tx effect of FOLFOX6 with pmab or bev in 1st-line WT KRAS mCRC. The PRIME study showed significantly improved progression free survival (PFS) and overall survival (OS) with pmab + FOLFOX vs FOLFOX in pts with WT RAS (KRAS/NRAS exons 2, 3, 4) mCRC in a prospective-retrospective analysis (unpublished data). Methods: This prospective-retrospective analysis of PEAK was designed to assess the effect of pmab + FOLFOX6 or bev + FOLFOX6 on PFS (primary endpoint) and OS in WT RAS (KRAS/NRAS exons 2, 3, 4) mCRC. Pts were required to have WT KRAS exon 2 tumors. Bidirectional Sanger sequencing and Transgenomic SURVEYOR/WAVE analysis were independently conducted to detect mutations in KRAS exon 3 (codons 59/61), exon 4 (codons 117/146); NRAS exon 2 (codons 12/13), exon 3 (codons 59/61), exon 4 (codons 117/146); BRAF exon 15 (codon 600) in banked specimens. Results: 285 WT KRAS (exon 2) mCRC patients (pts) were randomized, 278 received tx. The current RAS ascertainment rate is 75%. Tx HRs (pmab:bev) for pts with WT RAS were 0.63 (95% CI, 0.43-0.94; p = 0.02) for PFS and 0.55 (95% CI, 0.30-1.01; p = 0.06) for OS (Table). The incidence of worst grade 3-5 adverse events was consistent with the primary analysis. Updated OS and BRAF results will be presented. Conclusions: In this 1st-line estimation study in WT RAS mCRC, PFS and OS HR favored pmab + FOLFOX6 relative to bev + FOLFOX6, suggesting that activating RAS mutations appear to be predictive for pmab tx effect. The safety profile for both arms was consistent with previously reported studies. Clinical trial information: NCT00819780.

^a WT in KRAS and NRAS (exons 2, 3, 4). ^bWT KRAS (exon 2) and Mutant KRAS (exons 3 or 4) or Mutant NRAS (exons 2, 3, or 4). ^cStratified Cox proportional hazards model. ^dNot reached.