Comparison of uncommon EGFR exon 21 L858R compound mutations with single mutation.

Non-small-cell lung cancer with epidermal growth factor receptor (EGFR) mutation is sensitive to EGFR tyrosine kinase inhibitors (TKIs). But little is known about the response to EGFR TKIs and the prognostic role of compound mutations. This study compared the uncommon EGFR exon 21 L858R compound mutations with single mutation to characterize EGFR compound mutations and investigated their response to EGFR TKI treatment. We retrospectively screened 799 non-small-cell lung cancer patients from August 1, 2009 to June 1, 2012 by EGFR mutation testing. EGFR mutations were detected in 443 patients, with 22 (4.97%) compound mutations. Subsequently, six patients with EGFR exon 21 L858R compound mutations and 18 paired patients with single L858R mutation were well characterized. Finally, we also analyzed the EGFR TKI treatment response and patients' outcomes of compound or single L858R mutations. There was no differential treatment effect on the disease control rate and objective response rate between the L858R compound mutations and single mutation groups. No significant difference in overall survival or progression-free survival of these two groups was found by log-rank test. In conclusion, we demonstrated that no significant difference was detected in the response to EGFR TKIs and patients' outcomes in the compound and single mutation groups.