Association of KRAS G13D Tumor Mutations With Outcome in Patients With Metastatic Colorectal Cancer Treated With First-Line Chemotherapy With or Without Cetuximab

Purpose We investigated in the first-line setting our previous finding that patients with chemorefractory KRAS G13D-mutated metastatic colorectal cancer (mCRC) benefit from cetuximab treatment. Methods Associations between tumor KRAS mutation status (wild-type, G13D, G12V, or other mutations) and progression-free survival (PFS), survival, and response were investigated in pooled data from 1,378 evaluable patients from the CRYSTAL and OPUS studies. Multivariate analysis correcting for differences in baseline prognostic factors was performed. Results Of 533 patients (39%) with KRAS-mutant tumors, 83 (16%) had G13D, 125 (23%) had G12V, and 325 (61%) had other mutations. Significant variations in treatment effects were found for tumor response (P=.005) and PFS (P=.046) in patients with G13D-mutant tumors versus all other mutations (including G12V). Within KRAS mutation subgroups, cetuximab plus chemotherapy versus chemotherapy alone significantly improved PFS (median, 7.4 v 6.0 months; hazard ratio [HR], 0.47; P=.039) and tumor response (40.5% v 22.0%; odds ratio, 3.38; P=.042) but not survival (median, 15.4 v 14.7 months; HR, 0.89; P=.68) in patients with G13D-mutant tumors. Patients with G12V and other mutations did not benefit from this treatment combination. Patients with KRAS G13D-mutated tumors receiving chemotherapy alone experienced worse outcomes (response, 22.0% v 43.2%; odds ratio, 0.40; P=.032) than those with other mutations. Effects were similar in the separate CRYSTAL and OPUS studies. Conclusion The addition of cetuximab to first-line chemotherapy seems to benefit patients with KRAS G13D-mutant tumors. Relative treatment effects were similar to those in patients with KRAS wild-type tumors but with lower absolute values. J Clin Oncol 30:3570-3577. (C) 2012 by American Society of Clinical Oncology