KRAS and BRAF mutations in advanced colorectal cancer are associated with poor prognosis but do not preclude benefit from oxaliplatin or irinotecan: results from the MRC FOCUS trial.
OBJECTIVE
Activating mutation of the KRAS oncogene is an established predictive biomarker for resistance to anti-epidermal growth factor receptor (anti-EGFR) therapies in advanced colorectal cancer (aCRC). We wanted to determine whether KRAS and/or BRAF mutation is also a predictive biomarker for other aCRC therapies.


METHODS
The Medical Research Council Fluorouracil, Oxaliplatin and Irinotecan: Use and Sequencing (MRC FOCUS) trial compared treatment sequences including first-line fluorouracil (FU), FU/irinotecan or FU/oxaliplatin in aCRC. Tumor blocks were obtained from 711 consenting patients. DNA was extracted and KRAS codons 12, 13, and 61 and BRAF codon 600 were assessed by pyrosequencing. Mutation (mut) status was assessed first as a prognostic factor and then as a predictive biomarker for the benefit of adding irinotecan or oxaliplatin to FU. The association of BRAF-mut with loss of MLH1 was assessed by immunohistochemistry.


RESULTS
Three hundred eight (43.3%) of 711 patients had KRAS-mut and 56 (7.9%) of 711 had BRAF-mut. Mutation of KRAS, BRAF, or both was present in 360 (50.6%) of 711 patients. Mutation in either KRAS or BRAF was a poor prognostic factor for overall survival (OS; hazard ratio [HR], 1.40; 95% CI, 1.20 to 1.65; P < .0001) but had minimal impact on progression-free survival (PFS; HR, 1.16; 95% CI, 1.00 to 1.36; P = .05). Mutation status did not affect the impact of irinotecan or oxaliplatin on PFS or OS. BRAF-mut was weakly associated with loss of MLH1 staining (P = .012).


CONCLUSIONS
KRAS/BRAF mutation is associated with poor prognosis but is not a predictive biomarker for irinotecan or oxaliplatin. There is no evidence that patients with KRAS/BRAF mutated tumors are less likely to benefit from these standard chemotherapy agents.
Richman
Susan D
SD
Leeds Institute of Molecular Medicine, St. James's Institute of Oncology, Cancer Research UK Genomic Services, University of Leeds, Leeds, UK.
Seymour
Matthew T
MT
Chambers
Philip
P
Elliott
Faye
F
Daly
Catherine L
CL
Meade
Angela M
AM
Taylor
Graham
G
Barrett
Jennifer H
JH
Quirke
Philip
P
D048868:Adaptor Proteins, Signal Transducing / Q000032:analysis; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D014408:Biomarkers, Tumor / Q000032:analysis / Q000235:genetics*; D002166:Camptothecin / Q000008:administration & dosage / Q000031:analogs & derivatives; D015179:Colorectal Neoplasms / Q000737:chemistry / Q000188:drug therapy* / Q000235:genetics / Q000401:mortality / Q000473:pathology; D004252:DNA Mutational Analysis; D018572:Disease-Free Survival; D005472:Fluorouracil / Q000008:administration & dosage; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D000077146:Irinotecan; D053208:Kaplan-Meier Estimate; D053842:Microsatellite Instability; D000070957:MutL Protein Homolog 1; D009154:Mutation; D009687:Nuclear Proteins / Q000032:analysis; D009944:Organoplatinum Compounds / Q000008:administration & dosage; D000077150:Oxaliplatin; D018579:Patient Selection; D057285:Precision Medicine; D016016:Proportional Hazards Models; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D016283:Proto-Oncogene Proteins p21(ras); D018570:Risk Assessment; D013997:Time Factors; D016896:Treatment Outcome; D018631:ras Proteins / Q000235:genetics*
D048868:Adaptor Proteins, Signal Transducing; D014408:Biomarkers, Tumor; C117307:KRAS protein, human; C501486:MLH1 protein, human; D009687:Nuclear Proteins; D009944:Organoplatinum Compounds; D011518:Proto-Oncogene Proteins; D000077150:Oxaliplatin; D000077146:Irinotecan; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D000070957:MutL Protein Homolog 1; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins; D005472:Fluorouracil; D002166:Camptothecin