Introduction: With the approval of first-line osimertinib treatment in stage IV EGFR-mutated NSCLC, detection of resistance mechanisms will become increasingly important—and complex. Clear guidelines for analyses of these resistance mechanisms are currently lacking. Here, we provide our recommendations for optimal molecular diagnostics in the post-EGFR tyrosine kinase inhibitor (TKI) resistance setting. Methods: We compared molecular workup strategies from three hospitals of 161 first- or second-generation EGFR TKI–treated cases and 159 osimertinib-treated cases. Laboratories used combinations of DNA next-generation sequencing (NGS), RNA NGS, in situ hybridization (ISH), and immunohistochemistry (IHC). Results: Resistance mechanisms were identified in 72 first-generation TKI cases (51%) and 85 osimertinib cases (57%). RNA NGS, when performed, revealed fusions or exon-skipping events in 4% of early TKI cases and 10% of osimertinib cases. Of the 30 MET and HER2 amplifications, 10 were exclusively detected by ISH or IHC, and not detected by DNA NGS, mostly owing to low tumor cell percentage (<30%) and possibly tumor heterogeneity. Conclusions: Our real-world data support a method for molecular diagnostics, consisting of a parallel combination of DNA NGS, RNA NGS, MET ISH, and either HER2 ISH or IHC. Combining RNA and DNA isolation into one step limits dropout rates. In case of financial or tissue limitations, a sequential approach is justifiable, in which RNA NGS is only performed in case no resistance mechanisms are identified. Yet, this is suboptimal as—although rare—multiple acquired resistance mechanisms may occur.
|Journal||JTO Clinical and Research Reports|
|Publication status||Published - 1 Dec 2021|
Bibliographical noteFunding Information:
Disclosure: Dr. von der Thüsen reports receiving grants from AstraZeneca , Bristol-Myers Squibb , and Pfizer ; nonfinancial support from Roche; and personal fees from Merck Sharp & Dohme and Roche, outside of the submitted work. Dr. Dubbink reports receiving personal fees from AbbVie , AstraZeneca , Bayer, Janssen, and Eli Lilly and grants from AstraZeneca , Illumina, Merck Sharp & Dohme, and Pfizer, outside of the submitted work. Prof. Dingemans reports receiving personal fees from Roche, Eli Lilly, Pfizer, PharmaMar, Takeda, Boehringer Ingelheim, AstraZeneca, Jansen, Chiesi, Amgen, and Bayer and grants from AstraZeneca and Amgen, outside of the submitted work. Dr. de Langen reports receiving grants from Bristol-Myers Squibb, Merck Sharp & Dohme, Boehringer, and AstraZeneca and nonfinancial support from Merck Serono and Roche, outside of the submitted work. Prof. Smit reports receiving grants and other fees from AstraZeneca, during the conduct of the study. Prof. Postmus reports receiving personal fees from Boehringer Ingelheim, Merck Sharp & Dohme, and Bristol-Myers Squibb, outside of the submitted work. Dr. Monkhorst reports receiving grants from AstraZeneca; personal fees from Roche , Eli Lilly , Bayer, Boehringer Ingelheim, AstraZeneca , AbbVie, Merck Sharp & Dohme , and Bristol-Myers Squibb; and nonfinancial support from Takeda, Personal Genome Diagnostics, and Delfi, outside of the submitted work. The remaining authors declare no conflict of interest.
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