Early Detection of Triple Negative Breast Cancer Relapse (CUPCAKE)

Inclusion Criteria:

1. Patients must have signed a written informed consent before inclusion

2. Patients must be female ≥ 18 years old

3. Patients diagnosed with a non-metastatic TNBC (ER & PR <10%, HER2- per ASCO/CAPguidelines). Patients must have been previously evaluated by a 18F-FDG PET-CT or abone scintigraphy combined with a thorax, abdomen and pelvis CT scan with contrast

4. Patients who have undergone surgery with curative intent for their non-metastaticTNBC. Surgery must have been performed between 3 to 9 months before inclusion.Patients must have initiated their adjuvant therapy, whenever indicated, since atleast 12 weeks. For patients receiving an experimental adjuvant treatment in aclinical trial, any intervention planned as part of this trial must be completedbefore inclusion.

5. High-risk primary tumor, defined as:

6. Lack of pathological complete response after neoadjuvant chemotherapy (RCB I,II or III; RCB I being capped to a maximum of 30% of included patients) OR, inthe absence of neoadjuvant chemotherapy,

7. Stage IIB-III (i.e., T2N1, any T3-T4, any N2-3) OR

8. Any loco-regional relapse occurring after a prior ipsilateral, curativelytreated TNBC

9. No sign of local or distant relapse, as per investigator assessment

10. Performance status < 2

11. Available FFPE tumor block with > 10% cellularity or 11 tumor sections with >10%cellularity

12. Patient able to comply with protocol requirements

13. Patients covered by a health insurance

Exclusion Criteria:

1. Any uncontrolled disease, metabolic dysfunction, physical examination finding, orclinical laboratory finding or any other medical condition that, in the opinion ofthe investigator, interferes with the trial procedures

2. Male participants

3. Patients with altered mental status or psychiatric disorder that, in the opinion ofthe investigator, would preclude a valid patient informed consent.

4. Patients who have difficulty undergoing trial procedures for geographic, social orpsychological reasons

5. Person deprived of liberty or under guardianship

6. History of another primary malignancy except for the following :

7. Basal cell carcinoma or any in situ carcinoma treated with curative intent

8. Any stage I-II malignancy treated with curative intent with no evidence ofactive disease in the last five years

9. For step #2 (randomization after ctDNA detection): clinical/radiological metastaticrelapse before the detection of the molecular relapse.