KRAS Genotypes and Outcome in Patients With Chemotherapy-Refractory Metastatic Colorectal Cancer Treated With Cetuximab

To the Editor: Dr De Roock and colleagues¹ studied the effect of KRAS p.G13D mutation on cetuximab efficacy in chemotherapy-refractory metastatic colorectal cancer. The authors concluded that patients with KRAS p.G13D-mutated tumors have longer overall survival and progression-free survival than patients with other KRAS -mutated tumors.

In vitro data² suggest that KRAS p.G13D mutation and other KRAS mutations may have different biological effects. However, most studies evaluate the effect of KRAS mutations as a whole on cetuximab efficacy, estimating a mean effect that depends on the relative proportions of p.G13D and other mutations.^3- 4 De Roock et al compared p.G13D mutation with other KRAS mutations and with wild-type KRAS. However, the authors did not present data for the comparison between other KRAS mutations and wild-type KRAS. It would be interesting to know, in comparison with wild-type KRAS tumors, whether the clinical outcomes for patients with p.G13D mutations are better than for patients with other KRAS mutations.