Evaluation of the Technical Feasibility of Testing ct DNA for Homologous Recombination Gene Variants in Metastatic Prostate Cancer.

Evaluation of the Technical Feasibility of Testing Circulating Tumour DNA for Homologous Recombination Gene Variants in Metastatic Prostate Cancer.

Evaluation of technical feasibility for Homologous Recombination (HR) genes variants research on circulating tumor DNA (ctDNA) from plasma and urine of patients with a metastatic prostate cancer.

The benefit of PARPi has been well established for ovarian (SOLO-1 study) and prostate cancer (PROFOUND study) with defects in the Homologous Recombination Repair (HRR) system due to BRCA1 or BRCA2 variants. Somatic variants in HRR genes are currently researched by Next Generation Sequencing (NGS). However, in metastatic prostate cancer, using formalin-fixed and paraffin-embedded (FFPE) samples, failure rate is around 30 % according to our retrospective datas, in agreement with the data of the PROFOUND study, highlighting a real pre-analytical matter when FFPE samples are used for NGS testing. Research of such alterations on circulating tumor DNA (ctDNA) extracted from plasma or urine could be a promising alternative test.

Inclusion criteria

• Age > 18 years
• Metastatic prostate cancer
• Archived tissue sample available for testing for somatic variants of HRR genes (including BRCA1/BRCA2)
• Free, informed and signed consent for research

Non inclusion criteria

• Refusal of blood and urine collection
• Patient cognitively incapable of signing consent to participate in this study
• Patient under guardianship or curatorship