PLANET

Main inclusion criteria:

1. Male or female, ≥18 years of age on day of signing informed consent
2. Stage II or III TNBC prior to the start of neoadjuvant treatment
   1. Locally assessed stage II or III TNBC according to the primary tumor (T) and regional lymph node (N) staging as per the American Joint Committee on Cancer (AJCC) for breast cancer staging criteria version 8
   2. Locally assessed estrogen receptor (ER) and/or progesterone receptor (PR) expression <10% and HER2-negative according to the ASCO-CAP guideline
3. The patient has received neoadjuvant treatment with chemotherapy (containing at least anthracyclines and taxanes) and pembrolizumab, with a minimum of two 6-weekly (or four 3-weekly) cycles of pembrolizumab
4. The patient underwent breast surgery ≤12 weeks prior to inclusion in the study
5. The patient is scheduled to start standard of care adjuvant treatment with capecitabine or olaparib (pending reimbursement), based on non-pCR after neoadjuvant treatment, defined as RCB score >0
6. World Health Organization (WHO) performance status 0-2
7. Adequate organ function, as assessed ≤30 days prior to the screening:
   1. Absolute neutrophil count (ANC) ≥1,000/mm3 (1.0 x 10e9 /L)
   2. Platelets ≥50,000/mm3 (50 x 10e9 /L);
   3. Estimated creatinine clearance ≥ 30 mL/min as calculated using the method standard for the institution;
   4. Total serum bilirubin ≤1.5 x upper limit of normal (ULN) (≤3.0 x ULN if Gilbert’s disease);
   5. Aspartate aminotransferase (AST) and alanine transaminase (ALT) ≤3 x ULN
8. Participants of childbearing potential must be willing to use an adequate method of contraception for the course of the study through 6 months after the last dose of study medication
9. Willingness and ability to comply with scheduled visits, treatment plan, laboratory tests, and other study procedures
10. Willingness to provide written informed consent, according to the Good Clinical Practice (GCP) and national/local regulations

Exclusion criteria:

1. Contra-indications for any of the study drugs
2. Other invasive malignancies, except when treated with curative intent without chemotherapy AND more than 5 years ago
3. The presence of any psychological, familial, sociological or geographical condition potentially hampering compliance with the study protocol and follow-up schedule
4. Any other severe acute or chronic medical or psychiatric condition or laboratory abnormality that may increase the risk associated with study participation or may interfere with the interpretation of study results and, in the judgment of the investigator, would make the patient inappropriate for entry into this study