The predictive value of uncommon EGFR mutation in patients with non-small-cell lung cancer.

9028 Background: Non-small-cell lung cancers with uncommon epidermal growth factor receptor ( EGFR) mutations are regarded as a heterogeneous group with variable responses to EGFR-targeted drugs. Here we designed this retrospective study to describe the epidemiology and clinical outcomes of uncommon EGFR mutations in a Chinese cohort of lung cancer patients. Methods: Between June 2007 and June 2014, 5363 lung cancer patients whose EGFR genotyping was performed successfully at Guangdong Lung Cancer Institute (GLCI, Guangzhou, China) were screened. 1837 patients were included in the epidemiological analysis. The clinical outcome was analyzed in 97 advanced-stage patients harboring uncommon EGFR mutations with follow-up data. Results: 218 patients harbored uncommon EGFR mutations, making up 11.9% of all cancers with documented EGFR mutations. Compared with common mutants, those with uncommon mutations were more commonly found in smokers and male patients. The most frequently detected uncommon mutations were exon 20 insertions, G719X mutations and L858R complex mutations, occurring in 30.7%, 21.1% and 17.0% of all EGFR-uncommon-mutation cases. G719X and L858R complex mutations were associated with similar benefit from EGFR-TKI; median PFS was 15.2 (95% CI 8.7-21.7) and 11.6 (95% CI 3.6-19.6) months, respectively. T790M or 20INS was associated with a poorer EGFR-TKI response; median PFS was 1.0 (95% CI 0.0-2.2) and 3.0 (95% CI 1.3-4.7) months, respectively. Of note, two patients with 23% and 65% tumor shrinkages had N771_P772insN and H773_V774insQ, with PFS of 5.7 and 6.1 months respectively. Conclusions: Favorable responses were observed in specific subtypes including complex L858R and G719X, and our results suggested first-line EGFR-TKI should be preferable in such patients.