Patients with KRAS-mutant NSCLC showed poorer clinical outcomes when treated with erlotinib and chemotherapy....KRAS was successfully sequenced more often than EGFR because of the simpler sequencing strategy required. Single amino acid substitutions in codon 12 were most common (51 of 55), whereas codon 13 mutations were found in only four samples (Table 2 and Supplemental Fig 1).