Analysis of KRAS/NRAS Mutations in a Phase III Study of Panitumumab with FOLFIRI Compared with FOLFIRI Alone as Second-line Treatment for Metastatic Colorectal Cancer

Clin Cancer Res. 2015 Dec 15;21(24):5469-79. doi: 10.1158/1078-0432.CCR-15-0526. Epub 2015 Sep 4.

Abstract

Purpose: We evaluated the influence of RAS mutation status on the treatment effect of panitumumab in a prospective-retrospective analysis of a randomized, multicenter phase III study of panitumumab plus fluorouracil, leucovorin, and irinotecan (FOLFIRI) versus FOLFIRI alone as second-line therapy in patients with metastatic colorectal cancer (mCRC; ClinicalTrials.gov, NCT0039183).

Experimental design: Outcomes were from the study's primary analysis. RAS mutations beyond KRAS exon 2 (KRAS exons 3, 4; NRAS exons 2, 3, 4; BRAF exon 15) were detected by bidirectional Sanger sequencing in wild-type KRAS exon 2 tumor specimens. Progression-free survival (PFS) and overall survival (OS) were coprimary endpoints.

Results: The RAS ascertainment rate was 85%; 18% of wild-type KRAS exon 2 tumors harbored other RAS mutations. For PFS and OS, the hazard ratio (HR) for panitumumab plus FOLFIRI versus FOLFIRI alone more strongly favored panitumumab in the wild-type RAS population than in the wild-type KRAS exon 2 population [PFS HR, 0.70 (95% confidence interval [CI], 0.54-0.91); P = 0.007 vs. 0.73 (95% CI, 0.59-0.90); P = 0.004; OS HR, 0.81 (95% CI, 0.63-1.03); P = 0.08 vs. 0.85 (95% CI, 0.70-1.04); P = 0.12]. Patients with RAS mutations were unlikely to benefit from panitumumab. Among RAS wild-type patients, the objective response rate was 41% in the panitumumab-FOLFIRI group versus 10% in the FOLFIRI group.

Conclusions: Patients with RAS mutations were unlikely to benefit from panitumumab-FOLFIRI and the benefit-risk of panitumumab-FOLFIRI was improved in the wild-type RAS population compared with the wild-type KRAS exon 2 population. These findings support RAS testing for patients with mCRC. Clin Cancer Res; 21(24); 5469-79. ©2015 AACR.See related commentary by Salazar and Ciardiello, p. 5415.

Trial registration: ClinicalTrials.gov NCT00339183.

Publication types

  • Clinical Trial, Phase III
  • Multicenter Study
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Antibodies, Monoclonal / administration & dosage
  • Antineoplastic Combined Chemotherapy Protocols / adverse effects
  • Antineoplastic Combined Chemotherapy Protocols / therapeutic use*
  • Camptothecin / adverse effects
  • Camptothecin / analogs & derivatives*
  • Camptothecin / therapeutic use
  • Colorectal Neoplasms / drug therapy*
  • Colorectal Neoplasms / genetics*
  • Colorectal Neoplasms / mortality
  • Colorectal Neoplasms / pathology
  • DNA Mutational Analysis
  • Exons
  • Female
  • Fluorouracil / adverse effects
  • Fluorouracil / therapeutic use
  • Genes, ras*
  • Humans
  • Leucovorin / adverse effects
  • Leucovorin / therapeutic use
  • Male
  • Middle Aged
  • Mutation*
  • Neoplasm Metastasis
  • Panitumumab
  • Proportional Hazards Models
  • Proto-Oncogene Proteins B-raf / genetics
  • Retreatment
  • Survival Analysis
  • Treatment Outcome

Substances

  • Antibodies, Monoclonal
  • Panitumumab
  • Proto-Oncogene Proteins B-raf
  • Leucovorin
  • Fluorouracil
  • Camptothecin

Supplementary concepts

  • IFL protocol

Associated data

  • ClinicalTrials.gov/NCT00339183