Lung adenocarcinoma patients of young age have lower EGFR mutation rate and poorer efficacy of EGFR tyrosine kinase inhibitors

Patients aged ≤50 years are rarely diagnosed with nonsmall cell lung cancer. We conducted a retrospective cohort study to understand the mutation status of EGFR and the efficacy of epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) treatment in young Asian patients with lung adenocarcinoma. We collected tumour specimens and malignant pleural effusions from lung adenocarcinoma patients from June 2005 to April 2014, recorded their clinical demographic data, and analysed EGFR mutations by reverse transcriptase PCR. EGFR mutation data were collected from 1039 lung adenocarcinoma patients, including 161 patients aged ≤50 years and 878 patients aged >50 years. Fewer patients aged ≤50 years had EGFR mutations than older patients (p=0.043), but they showed a higher rate of uncommon EGFR mutations (p=0.035). A total of 524 patients with EGFR mutations received EGFR-TKI treatment, including 81 patients aged ≤50 years. Younger patients had a lower response rate than older patients (p=0.038) and had the shortest progression-free survival compared with other predefined age categories (p=0.033). Multivariate analysis of overall survival revealed age ≤50 years as a poor prognostic factor. In conclusion, fewer Asian patients aged ≤50 years had EGFR mutations, but the EGFR mutation types were more uncommon. Age ≤50 years is associated with poorer efficacy of EGFR-TKI treatment.