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S. Macmahon

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    Epidemiology and innovations in biomarker development (ID 42)

    • Event: ELCC 2017
    • Type: Poster Discussion session
    • Track:
    • Presentations: 1
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      95PD - Diagnostic EGFR testing with ctDNA versus tumour in patients with advanced non-small cell lung cancer (NSCLC): The Royal Marsden experience (ID 412)

      16:45 - 17:45  |  Author(s): S. Macmahon

      • Abstract

      EGFR inhibitors are approved for use in patients with EGFR mutant NSCLC. The cobas® platform is a companion diagnostic test used in clinical practice on tumour tissue, and is approved for ctDNA EGFR testing from plasma samples. We evaluated the diagnostic performance of this platform on ctDNA in a prospective single centre study.

      Patients diagnosed with advanced NSCLC at the Royal Marsden Hospital between November 2015 - November 2016 were included. Patients had to have tissue EGFR result available. Peripheral blood samples were collected in cfD tubes (Roche Molecular Solutions CA, USA) and analysed using the cobas® platform following manufacturer’s instructions.

      201 samples were analysed; median age 68 years. 89% of patients had adenocarcinoma, followed by poorly differentiated carcinoma (4%), squamous cell carcinoma (3%), adenosquamous (2.5%) and other (1.5%). 30% of patients were never smokers, whereas 58% were ex-smokers and 10% were current smokers (2% unknown smoking history). 93% of patients had stage 4 disease, whereas 7% had stage 3 disease. 42% of patients had thoracic-only disease. 79% of patients had their tissue EGFR analysis performed on the cobas[®] platform (others included Illumina NGS (7.5%); Therascreen[TM] (1%)). 10% of patients did not have available tumour tissue. All plasma samples were tested on the cobas[®] platform. Concordance rate between ctDNA and tumor was 87%, with sensitivity 65%, specificity 98%, positive predictive value 95%, and negative predictive value 85%. Concordance rate in patients with an EGFR mutation was 55% for thoracic-only disease and 75% for extra-thoracic disease. The mean time to EGFR result was shorter for ctDNA than tissue (8.4 vs 11.2 days; P=0.07) with a ctDNA failure rate of only 2.4%. Two tissue failures resulted in an EGFR mutation being picked up in plasma (Exon 19 and T790M).

      We demonstrate that ctDNA can be used for diagnosis of an EGFR mutation in advanced NSCLC with excellent specificity, despite moderate sensitivity. The cobas[®] test for ctDNA should be incorporated into clinical practice to triage patient care.

      Clinical trial identification:
      Not applicable

      Legal entity responsible for the study:
      The Institute of Cancer Research and the Royal Marsden NHS Foundation Trust

      Roche Molecular Solutions CA, USA

      T.A. Yap: Received research funding from Roche. S. Popat: Consultant to Roche and has received honoraria from Roche. J. Palma: Employee of Roche Molecular Solutions CA, USA. All other authors have declared no conflicts of interest.