Real-World Approach for Molecular Analysis of Acquired EGFR Tyrosine Kinase Inhibitor Resistance Mechanisms in NSCLC

Area of Science:

• Oncology
• Molecular Diagnostics
• Genetics

Background:

• The advent of first-line osimertinib for stage IV EGFR-mutated NSCLC necessitates robust methods for detecting resistance mechanisms.
• Current guidelines for analyzing these resistance mechanisms are insufficient, creating a need for standardized diagnostic approaches.

Purpose of the Study:

• To provide recommendations for optimal molecular diagnostics in the context of post-EGFR tyrosine kinase inhibitor (TKI) resistance.
• To evaluate and compare molecular workup strategies in real-world clinical settings.

Main Methods:

• A comparative analysis of molecular workup strategies across three hospitals.
• Inclusion of 161 first- or second-generation EGFR TKI-treated cases and 159 osimertinib-treated cases.
• Utilization of DNA next-generation sequencing (NGS), RNA NGS, in situ hybridization (ISH), and immunohistochemistry (IHC).

Main Results:

• Resistance mechanisms were identified in 51% of early TKI cases and 57% of osimertinib cases.
• RNA NGS detected fusions or exon-skipping events in 4% of early TKI cases and 10% of osimertinib cases.
• ISH or IHC exclusively detected 10 out of 30 MET and HER2 amplifications, often missed by DNA NGS due to low tumor cell percentage or heterogeneity.

Conclusions:

• A parallel combination of DNA NGS, RNA NGS, MET ISH, and HER2 ISH/IHC is supported by real-world data for molecular diagnostics.
• Simultaneous RNA and DNA isolation minimizes dropout rates.
• A sequential approach (RNA NGS only if initial tests are negative) is a less optimal alternative under resource constraints, risking missed multiple resistance mechanisms.