492P - Feasibility of rebiopsy and sequential treatment of EGFR tyrosine kinase inhibitors in real world patients with EGFR mutant non-small cell lung cancer

Abstract

BackgroundThe third generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) osimertinib is a standard treatment in case of T790M mutation positive after failure to first or second generation EGFR TKI in patients with EGFR-mutant non-small cell lung cancer (NSCLC). We investigated a success rate of rebiopsy and sequential EGFR TKI treatment in real world setting in Korea. MethodsWe retrospectively reviewed medical records of patients with EGFR mutant advanced NSCLC who received first- or second- generation EGFR TKI between Jan 2012 and Jun 2018 at a single center in Korea. ResultsAmong 221 patients with EGFR-mutant NSCLC, 68 patients who were lost to follow up (n = 19) or still on 1st- or 2nd- generation TKI (n = 49) at time of analysis were excluded. Forty-three out of remaining 153 patients (28%) did not have a chance of consideration for second line treatment because of deterioration of performance status (n = 21) or death (n = 22), especially in elderly over 70 years. Tests for acquired EGFR mutation were performed in 76% (84/110), among which 73 cases were tissue rebiopsy and 11 cases were plasma EGFR mutation analysis. Acquisition of tumor tissue in rebiopsy was successful in 93% (68/73). The most common reason of not doing rebiopsy was lack of sequential treatment options (n = 24). Ten patients with negative T790M or failure at initial rebiopsy underwent more than two times of repeated EGFR mutation analysis, among which four patients had eventually positive T790M at some point of disease course. Overall T790M positive rate was 54% (45/84). Among 7 patients with initially negative T790M mutation in plasma analysis, further rebiopsy from tumor tissue was performed only in one patients because of patient's refusal (n = 2), physician's decision to continue post-progression EGFR TKI (n = 2), poor performance status (n = 1), and unaccessibility to tumor tissue (n = 1). ConclusionsAbout 30% of patients with EGFR mutant NSCLC did not have a chance of consideration for second line EGFR TKI treatment, especially in elderly over 70 years. Success rate of tumor tissue rebiopsy was over 90% in real world setting, and repeated rebiopsy may increase detection rate of acquired T790M mutation. Legal entity responsible for the studyThe authors. FundingHas not received any funding. DisclosureAll authors have declared no conflicts of interest.