1257P - Influence of Smoking Status on Response to EGFR TKI – A Retrospective Analysis of Reflex EGFR Mutation Testing in Asian Patients with Advanced Lung Adenocarcinomas

Abstract

ABSTRACT Introduction Although the role of EGFR mutations (mt) is established in predicting response to EGFR TKI, there is little data on the impact of smoking on mt subtypes and treatment outcomes. We hypothesized that mt spectra differ between never-smokers (NS) and those with a smoking history (ex-smokers or current smokers) (SM), and that SM may have poorer outcomes to EGFR TKI. Methods All cases that had undergone reflex EGFR mt testing between 6/10 – 3/12 were reviewed for smoking status, performance status, patient demographics and type of EGFR mt. In patients who were treated with EGFR TKI, progression free survival (PFS) and 1-year overall survival (OS) was determined. Results 742 patients (M:F 384:358) were identified of which 342 (46.1%) were EGFR mt+. Majority were females 64.6% (n = 221, S:NS 15:197) while males comprised 35.4% (n = 121, S:NS 54:66). Mts in order of frequency: Exon (Ex) 19 deletions (del) (52.3%), L858R 33.9%, Ex 20 insertion (ins)/duplication (4.9%), G719X (4.1%), L861Q (1.8%), T790M (1.2%), and Exon 19 ins (0.3%). In patients with known smoking status and mt status, (n = 332), median age was 63 years in both NS (n = 261) and SM (n = 71). There was no significant difference in location of mt (Ex 18, 19, 20 and 21, p= 0.991), or the type of mt (Ex19 deletions vs. point mutations, p = 0.723). When we reviewed the clinical outcomes of 127 TKI naive patients (NS n = 103, SM n = 24) receiving gefitinib or erlotinib monotherapy with at least 6 months of follow up, median PFS was 11.9 months (m)and OS at 1 year was 75.3%. In subgroup analysis, PFS for NS vs. SM was 11.9 m and 14.7 m (p = 0.855) and 1 year OS 75.3% vs. 65.7% (p = 0.683). Conclusion EGFR mutations occur in 46% of patients in Singapore, of which one-fifth of patients had significant smoking history. Contrary to our hypothesis, the EGFR mt spectra and clinical outcomes is similar in NS vs. SM underscoring the importance of reflex testing in a population where mt prevalence is high. Disclosure All authors have declared no conflicts of interest.