A Cancer Gene Panel (CGP) including TP53 (as a control to confirm detection of tumor DNA) as well as BRCA1/2 and other HR-related genes, was analysed by Next Generation Sequencing (NGS) on matched tumor DNA from FFPE tissue samples and cftDNA from ascites from 53 patients presenting with advanced OC at Gustave Roussy’s cancer center. Here, BRCA1 is linked to cancer.