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C. Lupi
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P3.02b - Poster Session with Presenters Present (ID 494)
- Event: WCLC 2016
- Type: Poster Presenters Present
- Track: Advanced NSCLC
- Presentations: 1
- Moderators:
- Coordinates: 12/07/2016, 14:30 - 15:45, Hall B (Poster Area)
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P3.02b-027 - Detection of EGFR Mutations in Plasma of Lung Adenocarcinoma Patients Using Real-Time PCR and Mass Spectrometry (ID 5475)
14:30 - 14:30 | Author(s): C. Lupi
- Abstract
Background:
Lung adenocarcinoma patients harbouring sensitizing EGFR mutations can benefit from treatment with tyrosine kinase inhibitors (TKI). Whenever tumour tissue is inadequate or unavailable, detection of EGFR mutations in circulating cell-free tumour (ct) DNA from plasma is crucial to predict and monitor response to therapy. In this study we compared EGFR status between tumour tissue and plasma, using real-time PCR. Moreover, we evaluated the adequacy of ctDNA for a multi-target mass spectrometry (MS) analysis.
Methods:
EGFR mutations were investigated in paired plasma and tumour tissues from a prospective series of 105 lung adenocarcinoma patients: 79 had no prior TKI treatment and 26 underwent re-biopsy for TKI-acquired resistance. Molecular analyses were performed on tissue by a routine MS test (evaluation of 307 hot-spots in 10 genes including EGFR) and on ctDNA by a validated Scorpion/LNA real-time PCR (evaluation of 30 EGFR mutations). In the 26 postTKI patients ctDNA analysis was performed also by MS.
Results:
1-Plasma versus tissue by real-time PCR: overall sensitivity, specificity and concordance were 64.8%, 95.4% and 82%. In preTKI patients, 17 harboured EGFR sensitizing mutations on tissue,10 detected also in plasma (sensitivity 58.8 %, specificity 100%, concordance 91%). All 26 postTKI patients preserved EGFR sensitizing mutations. Regarding the detection of EGFR T790M resistance mutation, sensitivity, specificity and concordance were 63.6%, 80% and 73%. Specifically, 11 patients were T790M-positive (42%): 7 on both specimens, 4 only on tissue and 3 only on ctDNA. 2-Plasma versus tissue by MS: sensitivity, specificity and concordance for T790M were 50%, 93.3% and 76%. Particularly, 6 patients had a T790M-positive ctDNA: 5 concordant and 1 discordant with tissue; 4 T790M-positive cases on tissue were undetected in plasma; 1 sample was not evaluable.
Conclusion:
The real-time PCR on ctDNA showed a sensitivity consistent with literature and a high specificity, mostly in preTKI group. Concordance rates, influenced by biological and methodological factors, were lower in postTKI group. Indeed, some T790M mutations were detected only on ctDNA, which is expected to effectively mirror tumour heterogeneity better than bioptic samples, thus giving a global view of tumour. Finally, we demonstrated the adequacy of ctDNA for MS, in terms of quantity and quality. The use of a multi-target analysis on ctDNA might improve tumour characterization and response monitoring, evaluating important oncogenes other than EGFR, like PIK3CA, KRAS and BRAF. However, further studies are needed to better explore MS applicability on ctDNA.
