Comparison of Resistance Spectra after First and Second Line Osimertinib Treatment Detected by Liquid Biopsy.

Since 2009, several first, second, and third generation EGFR tyrosine kinase inhibitors (TKI) have been approved for targeted treatment of EGFR mutated metastatic non-small lung cancer (NSCLC). A vast majority of patients is improving quickly on treatment; however, resistance is inevitable and typically occurs after one year for TKI of the first and second generation. Osimertinib, a third generation TKI, has recently been approved for first line treatment in the palliative setting and is expected to become approved for the adjuvant setting as well. Progression-free survival (PFS) under osimertinib is superior to its predecessors but its spectrum of resistance alterations appears significantly more diverse compared to first and second generation EGFR TKI. As resistance mechanisms to osimertinib are therapeutically targetable in some cases, it is important to comprehensively test for molecular alterations in the relapse scenario. Liquid biopsy may be advantageous over tissue analysis as it has the potential to represent tumor heterogeneity and clonal diversification. We have previously shown high concordance of hybrid capture (HC) based next generation sequencing (NGS) in liquid biopsy versus solid tumor biopsies. In this study, we now present real-word data from 56 patients with metastatic NSCLC that were tested by liquid biopsy at the time of disease progression on mostly second line treated osimertinib treatment. We present examples of single and multiple TKI resistance mechanisms, including mutations in multiple pathways, copy number changes and rare fusions of RET, ALK, FGFR3 and BRAF. In addition, we present the added value of HC based NGS to reveal polyclonal resistance development at the DNA level encoding multiple EGFR C797S and PIK3CA mutations.

Integration of Tumor Mutation Burden and PD-L1 Testing in Routine Laboratory Diagnostics in Non-Small Cell Lung Cancer.

In recent years, Non-small cell lung cancer (NSCLC) has evolved into a prime example for precision oncology with multiple FDA-approved "precision" drugs. For the majority of NSCLC lacking targetable genetic alterations, immune checkpoint inhibition (ICI) has become standard of care in first-line treatment or beyond. PD-L1 tumor expression represents the only approved predictive biomarker for PD-L1/PD-1 checkpoint inhibition by therapeutic antibodies. Since PD-L1-negative or low-expressing tumors may also respond to ICI, additional factors are likely to contribute in addition to PD-L1 expression. Tumor mutation burden (TMB) has emerged as a potential candidate; however, it is the most complex biomarker so far and might represent a challenge for routine diagnostics. We therefore established a hybrid capture (HC) next-generation sequencing (NGS) assay that covers all oncogenic driver alterations as well as TMB and validated TMB values by correlation with the assay (F1CDx) used for the CheckMate 227 study. Results of the first consecutive 417 patients analyzed in a routine clinical setting are presented. Data show that fast reliable comprehensive diagnostics including TMB and targetable alterations are obtained with a short turn-around time. Thus, even complex biomarkers can easily be implemented in routine practice to optimize treatment decisions for advanced NSCLC.