ctDNA levels before treatment predict survival in non-small cell lung cancer patients treated with a tyrosine kinase inhibitor.

9542 Background: Currently there is an intense debate concerning therapeutic strategies in EGFR positive NSCLC patients with advance disease. Osimertinib is superior to standard EGFR Tyrosine Kinase Inhibitors (TKIs) as first line treatment. However, it is yet unclear whether this option is superior to sequential treatment of a 1st or 2nd generation TKI followed by osimertinib. In order to clarify this issue it is important to identify which patients are at high risk of progression disease. Methods: This is a prospective, multicentre, cross-sectional study promoted by Spanish Lung Cancer Group. 698 plasma samples from 196 advanced NSCLC patients with tumors harboring an EGFR activating mut…