Responsiveness to cetuximab without mutations in EGFR.

To the Editor: A large amount of information suggests that mutations in the kinase domain of epidermal growth factor receptor (EGFR) are critical for the efficacy of EGFR kinase inhibitors.1–3 However, the effect of EGFR mutations on the response to cetuximab has not been directly investigated. Barber et al.4 reported the absence of EGFR mutations in colorectal cancers and speculated that EGFR mutations were not required for the response to cetuximab, since it was an efficacious agent against this type of tumor.5 We sequenced the kinase domain of EGFR (exons 18, 19, and 21) in tumor samples from 38 . . .