953P EGFR mutation testing from pleural effusions of advanced lung adenocarcinoma patients in Serbia

Abstract

In Serbia, EGFR mutation testing is performed from liquid biopsy of lung cancer patients only by qPCR. The aim of this study was to evaluate the efficacy of this approach in pleural effusions of patients at diagnosis and after progression on EGFR-TKIs. Mutation testing was performed from blood and pleural effusions of advanced lung adenocarcinoma patients (stage IIIB or IV, ECOG performance status 0, 1, 2) using the Cobas® EGFR Mutation Test. In the period from 2016-2021, 124 patients were tested at baseline (53 % males, 47 % females, age range 37-83 years, median 61), and 104 after progression on first-line EGFR-TKIs (41 % males, 59 % females, age range 34-81 years, median 60). At diagnosis, 9 mutated samples were detected (7.3 %) with a turnaround time of 2 working days, and a 99.2 % testing success rate. At progression, an accordance rate of only 67 % with the initial driver mutation was observed from blood. The T790M mutation was detected in 34 patients (49 % of the mutated samples, 33% of total) which rendered them eligible for third-generation EGFR-TKIs. In the same period, only 6 samples (4.8 %) of pleural effusions were sent to our Laboratory along with blood, all from patients at progression. The testing was performed with a turnaround time of 2 working days, a 100 % testing success rate, and an accordance rate of 100 % with the initial driver mutation. In 3 samples (50 %), the T790M mutation was detected while the corresponding blood sample showed only the presence of the driver mutation. EGFR mutation testing from pleural effusion has proven valuable as an alternative liquid biopsy sample to blood, for detecting the T790M acquired resistance mutation in patients who progressed on first-line EGFR-TKIs in Serbia.