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EP1.01 - Advanced NSCLC (ID 150)
- Event: WCLC 2019
- Type: E-Poster Viewing in the Exhibit Hall
- Track: Advanced NSCLC
- Presentations: 1
- Now Available
- Coordinates: 9/08/2019, 08:00 - 18:00, Exhibit Hall
EP1.01-63 - The Usefulness of “Serum” Samples to Detect EGFR T790M Mutation in EGFR-TKI-Resistant Non-Small Cell Lung Cancer (Now Available) (ID 562)
08:00 - 18:00 | Presenting Author(s): Keigo Kobayashi
Osimertinib, a third-generation epidermal growth factor receptor-tyrosine kinase inhibitor, exerts remarkable effects against EGFR T790M resistance mutation-positive NSCLC. Identifying T790M mutation by re-biopsy is essential before prescribing osimertinib. Tissue biopsy is the golden standard for this purpose, but several factors limit its success rate. The liquid biopsy with blood, using circulating tumor DNA, has been an alternative method. However, the true biological meaning and equivalence of liquid biopsy and tumor biopsy are still under investigation. Especially, the usefulness of serum samples to detect T790M mutation is not yet been known.Method
We prospectively evaluated the sensitivity, specificity, and parallelism of the detection of EGFR mutations in tissue re-biopsy and liquid biopsy (plasma and serum), simultaneously, from June 2016 to May 2017. EGFR-mutations in tumor re-biopsy were evaluated by COBAS ver2 and peptide nucleic acid/locked nucleic acid PCR clamp method, and those in liquid biopsy were evaluated with COBAS ver2.Result
Fifteen patients were enrolled. In ten patients whose EGFR mutation was detected in liquid biopsy, the original EGFR mutation (exon 19 del or L858R) was detected in all patients. The detection rate of T790M was lower than that of the original EGFR mutation in liquid biopsy compared to that in tissue re-biopsy. The detection of T790M in serum exhibited a higher specificity (67%) and positive predictive value (50%) than that in plasma (50% and 40%, respectively). The detection sensitivity was similar in plasma and serum. Nine patients were treated with osimertinib. The RR was 77.8% and DCR was 100%. One patient who presented a response was positive for T790M in liquid biopsy (both plasma and serum) and negative in tissue re-biopsy.Conclusion
We suggest serum samples to be more useful than plasma samples for determining the effectiveness of osimertinib against relapse tumor sites because they were more reliable in the detection of T790M mutation at the relapse tumor tissue sites. Repeated tests with different samples and different methods may improve accuracy of T790M detection and will lead to the maximum benefit for the patient.
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