Author of

• 18974

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  P3.02 - Biology/Pathology (ID 620)

  • Event: WCLC 2017
  • Type: Poster Session with Presenters Present
  • Track: Biology/Pathology
  • Presentations: 1
  • Moderators:
  • Coordinates: 10/18/2017, 09:30 - 16:00, Exhibit Hall (Hall B + C)

  • 23949

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    P3.02-002 - Liquid and Solid Rebiopsies in EGFR-Mutated NSCLC Patients (ID 8442)

    09:30 - 09:30  |  Author(s): D. Nunes
    • Abstract

    Background:
    Treatment of EGFR-mutated NSCLC patients with acquired resistance to EGFR tyrosine kinase inhibitors (TKI) relies on identification of the mechanism of resistance.
    
    Method:
    We performed a retrospective multicentric study in order to investigate use and results of liquid (circulating free DNA) and solid rebiopsies in routine practice.
    
    Result:
    We included 95 EGFR-mutated NSCLC patients with at least one rebiopsy after treatment with EGFR TKI (mostly 1[st] generation TKI). 87 solid rebiopsies and 71 liquid rebiopsies were performed. The number of liquid biopsies increased over time, from 1/y (6,6% of all rebiopsies in 2014) to 53/y (70,6% of all rebiopsies in 2016). The proportion of liquid biopsies increased with the number of rebiopsies per patient, from 35,5% for the first rebiopsy to 83,3% for the third rebiopsy. The rebiopsy identified a mechanism of acquired resistance in 48 patients (50,5%), including 43 patients with a T790M mutation (45,2%), 2 patients (2,1%) with MET amplification, 1 patient (1%) with small cell lung cancer transformation, 1 patient (1%) with a C797S mutation and 1 patient (1%) with a KRAS mutation. The initial EGFR mutation was found in 74 solid rebiopsies (85%) and 43 liquid rebiopsies (60%). The T790M mutation was found in 32 solid rebiopsies (36,8%) and 18 liquid rebiopsies (25,3%). Among 44 patients having both liquid and solid rebiopsies performed at the same time, an EGFR mutation was found by both techniques in 26 cases (59,1%) and the overall concordance was 88,6%. Analysis of cerebrospinal fluid was positive in 10 patients (100%) for the initial EGFR mutation and 1 patient (10%) for the T790M mutation. A T790M mutation was identified in 37,3% of all first rebiopsies. Repeated rebiopsies when the first biopsy was negative identified the T790M mutation in 29,6% of cases.
    
    Conclusion:
    In our series representative of daily practice, rebiopsies of EGFR-mutated NSCLC patients with acquired resistance to EGFR TKI identified a mechanism of resistance in half of the cases. Repeating rebiopsies increased the chance of detecting a T790M mutation.