Molecular changes in epidermal growth factor receptor (EGFR) in non-small cell lung cancer (NSCLC) biopsies at time of progression compared to initial biopsy

Abstract

e22066 Background: EGFR mutations predict sensitivity and clinical outcome to tyrosine kinase inhibitors (TKI) in NSCLC. The two most commonly described mutations are Exon 19 deletion and Exon 21 L858R missense mutations. Genetic alterations over time have been described in other tumour types, but studies assessing EGFR genotypic changes with lung cancer progression are lacking. We sought to compare EGFR mutational status from lung tumors at time of recurrence or progression with the primary tumor. Methods: Using the Jewish General Hospital lung cancer database, of all patients diagnosed with NSCLC since 1999, those with biopsies at two different points in time were identified. All tumour samples were genotyped for EGFR exons 19 and 21 mutations using denaturing high performance liquid chromatography (dHPLC). Results: 29 patients were identified. Data for 12 patients, whose time of recurrence or progression varied between 4 months and 6 years, are available at this time. Of 12 patients, one had EGFR exon 19 mutation at time of diagnosis. One patient who initially displayed no EGFR mutation was found to have an exon 19 deletion at time of recurrence. The one with exon 19 at time of initial diagnosis continued to express exon 19 in the second biopsy. Conclusions: To our knowledge, this is the only study assessing changes in molecular genotype using dHPLC between primary and recurrent or progressive lung cancer biopsy specimens. Although sample size is small, it is evident that changes in EGFR mutational status can occur. Further prospective studies are required to determine how commonly molecular changes occur. No significant financial relationships to disclose.