This is an interventional (category 2), prospective, multicentric cohort study designed to demonstrate that the search, based on Circulating tumour DNA analysis, for a BRCA1/2 reversion mutation leading to restoration of its protein function enables early identification of disease progression in BRCA1/2 mutant patients treated as first-line maintenance with a PARP inhibitor (Olaparib alone or in combination with bevacizumab) for ovarian cancer.

For this study, a total of 9 blood samples will be taken from patients who will undergo a full 24-month treatment regimen.

Apart from the study procedure (blood sampling), all examinations carried out in this study, treatment with Olaparib (alone or combined with bevacizumab) and patient follow-up procedures will be carried out as part of routine care in accordance with the standard practices of each investigating site.

130 patients will take part in the study, and each patient will be followed for 24 months.

Inclusion Criteria:

1. Patient with an epithelial ovarian cancer, fallopian tube cancer or primitive of the peritoneum.
2. Patient with a BRCA 1 or 2 somatic and/or constitutional mutation previously confirmed and validated by an approved laboratory.
3. Patient due to start first-line maintenance treatment with Olaparib alone (PARP inhibitor) or in combination with bevacizumab.
4. Age ≥ 18 years at the time of signing the consent.
5. WHO ≤ 1.
6. Patient affiliated to a Social Security scheme in France.
7. Patient having signed informed consent prior to inclusion in the study and prior to any specific procedure for the study.

Exclusion Criteria:

1. Other cancer under treatment.
2. Olaparib treatment already initiated.
3. Indication for treatment with a PARP inhibitor other than Olaparib.
4. Any pathology contraindicating the sample collection procedures required by the study.
5. Any psychological, family, geographical or sociological condition that makes it impossible to comply with medical monitoring and/or the procedures laid down in the study protocol.
6. Subjects deprived of their liberty or under legal protection.