Limited data from the Indian subcontinent has shown prevalence of epidermal growth factor receptor (EGFR) gene activating mutations (AM) to be 22–40%. The current study aimed to assess prevalence of and clinicopathologic correlations of EGFR gene AM in North India.
Retrospective analysis of NSCLC patient cohort who underwent testing for EGFR gene mutations (n = 186) over a 3-year period (2012-2014). EGFR mutations were tested using PCR amplification and direct sequencing. Patients were classified into three groups: EGFR AM (Group1), EGFR wild type (Group 2) and EGFR unknown (UKN; uninterpretable test Group 3). Histologically adenocarcinomas (ADC) were further categorized as per IASLC 2011 classification. First line therapy was EGFR-TKI in Group 1 and platinum based doublet chemotherapy in Groups 2 and 3.
Mean age was 58.2 years. Majority of patients had ADC (93.5%), metastatic disease (71.3%) and were smokers (51.9%). There were 26, 131 and 29 patients in groups 1, 2 and 3 respectively. Most common EGFR AM was exon 19 deletion (n = 19) followed by exon 21 L858R mutation (n = 6). Female sex (p = 0.002), never smoking status (p = 0.002), stage IV disease (p = 0.032) and non-solid subtype of ADC (p = 0.001) were associated with EGFR AM on univariate logistic regression. On multivariate analysis, non-solid ADC was the only factor associated with EGFR AM. Median overall survival (OS) was highest in group 1 (750 days), intermediate in group 2 (459 days, p = 0.141 vs group 1), and least in group 3 (291 days, p = 0.027 vs group 1). In patients with stage IV disease, OS was higher in group 1 compared to group 2 (750 vs 278 days, p = 0.024). On univariate Cox Proportional analysis, smoking, poor PS (ECOG ≥2), EGFR UKN status and solid ADC were associated with worse OS. Female sex and lepidic ADC were associated with better OS. On multivariate analysis, lepidic ADC (H.R: 0.115) was the only factor associated with better OS.
Prevalence of EGFR AM (16.6%) in our cohort is less than that seen in East Asians and similar to that in western world. Histologic subtyping of ADC is independently associated with presence of EGFR AM and with better OS. EGFR AM are a positive prognostic factor for OS.
Clinical trial identification
All authors have declared no conflicts of interest.