PARP-inhibitor on Advanced Metastatic Breast Cancer in Germline PALB2 Mutations Carriers

Inclusion Criteria: * Adult patients over 18 years * PALB2 germline heterozygous mutation carrier, wild type BRCA1\&2 (breast cancer 1\&2) affected with metastatic breast cancer in first metastatic treatment line or beyond * Histologically or cytologically confirmed breast cancer with evidence of metastatic disease. * Triple Negative breast cancer; Patients affected with triple negative cancers should have received anthracyclines and taxanes in neo/adjuvant therapy. * Or patients with Hormonal receptor positive (HR+)/ Human epidermal growth factor receptor 2 negative (HER2-) breast cancer, with treatment failure after a second line of therapy; Estrogen Receptor/ProgesteroneReceptor breast cancer positive patients must have received and progressed on currently recommended therapies in this indication (endocrine therapy, CDK4/6 inhibitors (adjuvant or metastatic)), or have a disease form that the treating physician believes to be inappropriate for recommended therapies in this indication. * Prior therapy with an anthracycline and a taxane in an adjuvant setting. * Prior platinum allowed as long as no breast cancer progression occurred on treatment or if given in adjuvant/neoadjuvant setting, at least 12 months elapsed from last dose to study entry. * Eastern Cooperative Oncology Group (ECOG) performance status 0-2. * Adequate bone marrow, kidney and liver function. * Patients without visceral crisis Exclusion Criteria: * Patients with HER2 positive disease. * Untreated and/or uncontrolled brain metastases. * Patients in visceral crisis requiring chemotherapy * Cytopenia, defined with the following thresholds: (i) Neutrophil count \< 1500/mm3; Platelet count\< 100 000/mm3; Hemoglobin \<9g/dL * Prior malignancy unless curatively treated and disease-free for \> 5 years prior to study entry. Prior adequately treated non-melanoma skin cancer, in situ cancer of the cervix, ductal carcinoma in situ (DCIS) or stage I grade 1 endometrial cancer allowed. * Known HIV (Human Immunodeficiency Virus) infection. * Pregnant or breast-feeding women. * Lack of affiliation to a social security benefit plan (as a beneficiary or assignee)