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D.A.M. Heideman



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    P3.06 - Poster Session 3 - Prognostic and Predictive Biomarkers (ID 178)

    • Event: WCLC 2013
    • Type: Poster Session
    • Track: Biology
    • Presentations: 1
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      P3.06-024 - Retrospective analysis of rebiopsies in a cohort of EGFR-mutated NSCLC-patients with TKI-resistance; incidence of the T790M mutation. (ID 2162)

      09:30 - 09:30  |  Author(s): D.A.M. Heideman

      • Abstract

      Background
      Epidermal Growth Factor Receptor mutated (EGFR+) NSCLC patients have a median progression free survival (PFS) of approximately 12 months when treated with EGFR-tyrosine kinase inhibitors (TKI). One of the resistance mechanisms described is the T790M mutation. This mutation is reported in 49-65% of patients who are rebiopsied at disease progression. Here, we report on the incidence of T790M mutation in a cohort of patients who were sequentially rebiopsied.

      Methods
      EGFR+ patients or with TKI-response>24weeks and progressive disease on TKI’s were retrospectively analysed. Patients should have had at least 2 separate biopsies. All biopsies and treatments were collected from the medical record and pathological reports. Survival was calculated according to Kaplan-Meier. Overall survival (OS) was calculated from date of 1[st] diagnosis until death or June 2013, which ever was first

      Results
      68 patients with 2 biopsies or more were available for analysis. In the first biopsy at TKI-resistance; T790M mutation was detected in 34 patients (50,0%). 26/68 patients had later biopsies available; showing gain and loss of T790M in later biopsies (figure 1). Overall development of T790M was 57.4% (39/68). 7 patients had >3 biopsies available (figure 2). Patients developing T790M had numerically longer median OS of 3.8 years (range 2.8 – 4.9) as compared to median OS in T790M-patients (2.5 years, range 1.0 – 3.9) (P = 0.204).Figure 1Figure 2

      Conclusion
      57.4% of patients developed T790M. OS in patients developing T790M was longer than in patients not developing T790M, however the difference was not significant. Sequential data show that some patients ‘loose’ the T790M later on in the course of the disease. Data from this cohort suggests that T790M development is a dynamic process.