Study Evaluating DNA Double-strand Breaks (DSBs) REpair Factors (POLQ, Shieldin Complex and 53BP1) Expression as Biomarker of PARP Inhibitor Resistance in Patients With Deleterious Germline Mutation in BRCA 1/2 and HER2-negative, Metastatic or Locally Advanced Breast Cancer.

The purpose of this study is to assess whether expression of not only POLQ/Polθ, but also Shieldin complex and/or 53BP1 are correlated with primary and/or acquired resistance to PARPi (Poly(ADP-Ribose) Polymerases inhibitors) in a sub-population of locally advanced or metastatic breast cancer patients and vary regarding type and location of gBRCA1/2 mutations. This translational research program is composed of two multicentric, non-randomized prospective studies in patients with HER2-negative locally advanced or metastatic breast cancer: * The main study concerns 80 patients eligible for PARPi (according to the investigators).PARPi treatments (talazoparib or olaparib) will be administered and dosed according to the standard of care administration. * The sub-study concerns 40 patients in progression disease under PARPi alone. For each included patient in the main study or sub-study, tumor biopsy specimen and blood samples will be collected at different times during the study.

NCT Number	NCT05378204
Lead Sponsor	Institut Claudius Regaud
Conditions	Breast Cancer
Enrollment	120 participants
Start Date	2022-06-23
Primary Completion	2027-01 (estimated)
Study Completion	2027-06 (estimated)
Updated on ClinicalTrials.gov	2026-02-20