Author of

• 14490

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  P2.04 - Poster Session/ Biology, Pathology, and Molecular Testing (ID 234)

  • Event: WCLC 2015
  • Type: Poster
  • Track: Biology, Pathology, and Molecular Testing
  • Presentations: 1
  • Moderators:
  • Coordinates: 9/08/2015, 09:30 - 17:00, Exhibit Hall (Hall B+C)

  • 14582

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    P2.04-092 - Sequencing of Actionable EGFR Mutations from PtDNA in NSCLC: A Feasibility Study of Non-Invasive Analysis of Sensitivity to TKI (ID 984)

    09:30 - 09:30  |  Author(s): M. Castiglia
    • Abstract

    Background:
    In ~10 % of Caucasian patients with non-small cell lung cancer (NSCLC), the presence of an activating epidermal growth factor receptor (EGFR)-mutation has resulted in a more favourable prognosis by its exquisite sensitivity to a targeted treatment with tyrosine kinase inhibitors (TKI’s). However, in up to 20% of those patients, the presence of "driver" alterations cannot reliably be established due to an inadequate diagnostic sample and/or impossibility to re-biopsy a patient. Activating EGFR-mutations can be accurately detected in plasma with a high concordance to matched tumour tissue with allele-specific PCR assays of plasma tumor DNA (ptDNA). This ‘liquid biopsy’ can replace response to treatment, allow detection of early relapse in the follow-up and estimate prognosis. The aim of this study is to assess the feasibility of detecting ptDNA in patients with EGFR mutations, to assess the concordance of ptDNA levels to mutations in matched tissue samples and to correlate ptDNA levels with clinical response or relapse after start of TKI-treatment.
    
    Methods:
    Tumour tissue samples of 20 patients (10 with/10 without activating EGFR-mutations), was assessed for the presence of the respective mutation in matched ptDNA, obtained either at presentation or during follow up. DNA was extracted from aliquots (1ml) of plasma with the use of QIamp circulating nucleic acid kit (Qiagen). The target DNA is amplified and detected on the cobas z 480 analyzer using the amplification and detection reagents provided in the cobas EGFR Mutation Test kit. The concordance was estimated with Bayesian variables.
    
    Results:
    26 tissue and 34 plasma samples were collected from 20 Caucasian patients with median age of 67 years (54 to 84), 60% female, 30% non-smokers, 100% adenocarcinomas and 95% histologically or cytologically confirmed stage IV NSCLC. The median number of samples per patient was 3 (2 - 5). In the tissue samples 6 patients had an exon 19 deletion, 1 had exon 18 mutation, 2 had exon 20 mutation and in 1 patient a simultaneous exon 19 deletion and T790M mutation. The Bayesian characteristics of ptDNA determination are as follows:

    		A: at sample level ( n = 34)	B: at study population level (n = 20)
    1.	Prevalence of mutation	8.8%	10%
    2.	Sensitivity	12.5%	20%
    3.	Specificity	100%	100%
    4.	PPV	100%	100%
    5.	NPV	32.2%	55%
    6.	Accuracy	38%	60%
    7.	Concordance	11.5%	7.7%

    
    
    Conclusion:
    Detection of ptDNA in EGFR-positive patients is feasible. However, ptDNA mutation testing by cobas[R] 4800_Blood Test was not reliable due to the low analytical sensitivity and the heterogeneity of the patient population. Further studies with other methods as next-generation sequencing or digital droplet PCR are warranted.