2019 ASCO Annual Meeting!
Session: Lung Cancer—Non-Small Cell Metastatic
Type: Poster Session
Time: Sunday June 2, 8:00 AM to 11:00 AM
Location: Hall A
Tissue-based molecular and histological landscape of acquired resistance to osimertinib given initially or at relapse in patients with EGFR-mutant lung cancers.
Metastatic Non-Small Cell Lung Cancer
Lung Cancer—Non-Small Cell Metastatic
2019 ASCO Annual Meeting
Poster Board Number:
Poster Session (Board #351)
J Clin Oncol 37, 2019 (suppl; abstr 9028)
Author(s): Adam Jacob Schoenfeld, Joseph Minhow Chan, Hira Rizvi, Natasha Rekhtman, Yahya Daneshbod, Daisuke Kubota, Jason C. Chang, Maria E. Arcila, Marc Ladanyi, Romel Somwar, Mark G. Kris, Dana Pe'er, Gregory J. Riely, Helena Alexandra Yu; MSKCC, New York, NY; Memorial Sloan Kettering Cancer Center, New York, NY; Department of Pathology, Memorial Sloan Kettering Cancer Center, New York, NY; Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, NY
Background: Even though osimertinib (osi) is now the initial treatment for patients with EGFR-mutant lung cancers, our knowledge about mechanisms of resistance (MOR) is largely derived from patients who received osi after developing acquired resistance to initial EGFR inhibitor. Further, studies of osi resistance to date have mainly reported genotyping of plasma which suboptimally detects lineage plasticity, copy number changes, and chromosomal rearrangements. Methods: To identify MOR to osi and characterize clinical, molecular and histologic factors associated with duration of response, we identified patients with EGFR-mutant lung cancers who had next-generation sequencing performed on tumor tissue after developing acquired resistance to osi. Results: From January 2016 to December 2018, post-osi tumor tissue was collected from 71 patients (42 with paired pre-treatment specimens). See mechanisms of resistance below. Histologic transformation was identified in 19% of initial cases and 14% of all cases. When osi is given as initial treatment, with median follow up of 17 months, early emerging MOR rarely included on-target resistance mechanisms (1/16 cases of acquired EGFR G724S). Acquired alterations representing potential resistance mechanisms included CCNE1 and MYC amplifications, and mutations in MTOR and MET H1094Y. We confirmed in preclinical studies that an amino acid substitution at MET H1094 can reduce sensitivity to osi. Conclusions: In this analysis of MOR identified on NGS from tumor tissue, we found a different spectrum of resistance mechanisms to initial and later-line osi, with histologic transformation (including squamous cell transformation) a dominant MOR, particularly in the first-line setting, that cannot be identified on plasma testing. Subsequent studies are needed to assess patients with a longer time on initial osi as there may be a temporal bias to MOR, with off-target MOR emerging earlier and on-target resistance mutations later.
|First line (n = 16)||Later line (n = 55)||All (n = 71)|
|Small cell transformation||1||4||5|
|On target mutation (EGFR C797X or other)||1||10||11|
|Loss of T790M||-||17||17|
|Fusions (ALK, RET, BRAF)||0||5||5|
|Amplifications (HER2, MET, EGFR)||2||7||9|
|Off target mutations (KRAS, BRAF, HER2)||1||4||5|