This is a prospective interventional single-site research with a collection of biological samples.

The primary objective of the trial is to assess the ability of the "new technology" to isolating circulating tumor cells (CTC) in selected cancer patients.

Five groups will be constitued: at first the Group 0: Healthy volunteers included for the spike-in test; and then the four groups, Group1: Metastatic HER2-positive breast cancer; Group 2: Advanced CA-125 positive ovarian cancer; Group 3: Metastatic PSA-positive castrate-resistant prostate cancer; Group 4: Healthy volunteers included as control).

In each group, the percentage of cases with identified circulating tumor cells will be estimated.

This is a prospective interventional single-site research with a collection of biological samples ("Recherche Impliquant la Personne Humaine de type 2" according to French legislation).

First, a cohort of 20 healthy volunteers (Group 0: Healthy volunteers included for the spike-in test) will be constituted for the spike-in-test.

Then, recruitment of the three groups of 14 patients each (Group1: Metastatic HER2-positive breast cancer; Group 2: Advanced CA-125 positive ovarian cancer; Group 3: Metastatic PSA-positive castrate-resistant prostate cancer) and the control group of 14 healthy volunteers (Group 4: Healthy volunteers included as control) will be done in parallel.

In each group, the percentage of cases with identified circulating tumor cells will be estimated. Success will be defined as follows: the new technique has isolated putative circulating cells that have been confirmed as tumor cells by the immuno-histochemistry approach.

Circulating tumor cells (CTC) will be identified as followed:

• Group 1 - putative circulating cells isolated by the new technique must be tested as HER-2 positive using Fluorescence In Situ Hybridization (FISH) to be regarded as true CTC
• Group 2 - putative circulating cells isolated by the new technique must be tested as CA 125-positive using immuno-histochemistry (IHC) to be regarded as true CTC
• Group 3 - putative circulating cells isolated by the new technique must be tested as PSA-positive using IHC to be regarded as true CTC For the healthy volunteers included as controls, if putative circulating cells are observed, these healthy volunteers will be tested against the three markers (HER2, CA-125 and PSA).

Failure will be defined as follows: the technique failed to identify circulating tumor cells, either due to a technical issue, or because there was no cell identified by the new technique, or lastly because the identified cells were negative by the standard FISH or IHC technique.

The different characteristics of these cells will be described: size, cytological characteristics, number, etc.

Secondary collected samples will be frozen, and new technique for isolation of CTC will be applied a second time to describe the impact of freezing to the capacity for isolating the CTC.

The primary objective of the trial is to assess the ability of the "new technology" to isolating circulating tumor cells (CTC) in selected cancer patients.

Inclusion Criteria:

• Age ≥ 18 years old
• Registered with a social security system
• Signed, IRB-approved written informed consent
• Belonging to one of the following group:
• Group 1 - HER-2 positive breast cancer, defined as followed: histologically-proven, HER-2 positive breast cancer, with metastasis (stage IV) requiring first-line treatment
• Group 2 - Advanced ovarian cancer, defined as followed: histologically-proven, stage III or IV ovarian cancer requiring first-line chemotherapy
• Group 3 - Metastatic prostate cancer, defined as followed: histologically-proven, stage IV, castrate-resistant prostate cancer requiring chemotherapy with docetaxel or treatment with 2nd generation hormonal therapy (e.g. enzalutamide or abiraterone)
• Groups 0 and 4 - Healthy volunteers defined as followed: No prior personal history of malignant disease

Exclusion Criteria:

• Pregnant or breastfeeding woman
• Patient under guardianship or curatorship