The clinical benefit of bevacizumab in metastatic colorectal cancer is independent of K-ras mutation status: analysis of a phase III study of bevacizumab with chemotherapy in previously untreated metastatic colorectal cancer.
OBJECTIVE
Mutations of the K-ras gene were identified as a prognostic marker in metastatic colorectal cancer (mCRC). In addition, emerging data suggest that K-ras mutations are a negative predictor of clinical benefit from anti-epidermal growth factor receptor treatment in mCRC. Previously reported data suggest that the longer overall survival (OS) observed with bevacizumab treatment in mCRC is independent of alterations in the Ras/Raf/Mek/Erk pathway. We conducted additional analyses to better describe the clinical benefit of bevacizumab treatment in mCRC relative to K-ras mutation status.


METHODS
Additional statistical analyses were done with data from K-ras mutation analyses in 230 patients who were treated with irinotecan, fluorouracil, and leucovorin (IFL) in combination with either bevacizumab or placebo in a randomized phase III study. Following microdissection, tissue was subject to DNA sequencing to identify K-ras mutations in codons 12 and 13. Hazard ratios for the bevacizumab group relative to the control group were estimated from an unstratified Cox regression model. The median progression-free survival (PFS), OS times, and objective response rates were compared.


RESULTS
K-ras status was assessed in 230 patients (28.3%). The median PFS was significantly longer in bevacizumab-treated patients with wild-type (wt)- (13.5 versus 7.4 months; hazard ratio 0.44, p < .0001) and mutant (m)-K-ras (9.3 versus 5.5 months; hazard ratio 0.41, p = .0008). A significantly higher response rate for IFL plus bevacizumab was observed only in wt-K-ras patients (60.0% versus 37.3%, p = .006) compared with 43.2% versus 41.2% in the m-K-ras group.


CONCLUSIONS
Bevacizumab provides significant clinical benefit in patients with mCRC expressing either mutant or wild-type K-ras.
Hurwitz
Herbert I
HI
Duke University Medical Center, Division of Hematology & Oncology, Durham, NC 27710-0001, USA. hurwi004@mc.duke.edu
Yi
Jing
J
Ince
William
W
Novotny
William F
WF
Rosen
Oliver
O
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D020533:Angiogenesis Inhibitors / Q000008:administration & dosage*; D000911:Antibodies, Monoclonal / Q000008:administration & dosage*; D061067:Antibodies, Monoclonal, Humanized; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D000068258:Bevacizumab; D002166:Camptothecin / Q000008:administration & dosage / Q000031:analogs & derivatives; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000235:genetics*; D018572:Disease-Free Survival; D005260:Female; D005472:Fluorouracil / Q000008:administration & dosage; D011905:Genes, ras; D006801:Humans; D000077146:Irinotecan; D002955:Leucovorin / Q000008:administration & dosage; D008297:Male; D008875:Middle Aged; D009154:Mutation; D011237:Predictive Value of Tests
D020533:Angiogenesis Inhibitors; D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000068258:Bevacizumab; D000077146:Irinotecan; D002955:Leucovorin; D005472:Fluorouracil; D002166:Camptothecin