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MINI 26 - Circulating Tumor Markers (ID 148)
- Event: WCLC 2015
- Type: Mini Oral
- Track: Biology, Pathology, and Molecular Testing
- Presentations: 1
MINI26.11 - Longitudinal Monitoring of EGFR Mutations in Plasma of EGFR Mutant NSCLC Patients Treated with EGFR TKIs: Korean Lung Cancer Consortium (ID 1130)
16:45 - 18:15 | Author(s): M. Mao
Detection of epidermal growth factor receptor (EGFR) mutation in non-small cell lung cancer (NSCLC) patients is mainly based on tissue biopsy, which is invasive and time consuming. Furthermore, there is still a need for serial monitoring of EGFR mutations and detection of EGFR tyrosine kinase inhibitors (TKIs) resistance. We hypothesized that plasma-based EGFR mutation analysis may be feasible for monitoring response to EGFR TKIs and could be used to predict the resistance.
From January 2012 to October 2014, 200 EGFR mutant NSCLC patients were enrolled and treated with EGFR TKIs (141 patients for gefitinib, 46 patients for erlotinib, and 13 patients for afatinib). Plasma samples were prospectively obtained every 2 months from baseline until disease progression. The longitudinally collected plasma samples (n = 368) from 81 patients who progressed were analyzed using droplet digital PCR (ddPCR). We identified an association between serial EGFR mutant titers in plasma cell-free DNA (cfDNA) samples and the patient’s clinical response to EGFR TKIs.
Of a total 58 baseline cfDNA samples available for ddPCR, 43 (74%) samples demonstrated same mutation in the matched tumors (i.e. sensitivity: 70.8% (17/24) for L858R vs 76.5% (26/34) for exon 19 deletions). The concordance rate of plasma with tissue results of EGFR mutation was 88% for L858R and 86% for exon 19 deletion, respectively. Of the 54 patients with both before and after treatment plasma samples, 40 patients showed a dramatic decrease of mutant copies (greater than 50%) in blood in the first 2 months after treatment. We also found the secondary mutation (T790M) emerged in 28 patients around 3~13 months after treatment and in 4 patients before the treatment. Elevated circulating mutations (L858R/ex19/T790M) can be detected in 5 patients before disease progression as determined by CT scan.
These results suggest that ddPCR is an appropriate method for determining plasma-based EGFR mutation status and may aid in monitoring response to EGFR TKIs and early detection of EGFR TKIs resistance.
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