Inclusion Criteria:  Stage I to III breast cancer with surgical resection of the primary tumor that is confirmed to be either: TNBC, irrespective of BRCA status or HR+/HER2- breast cancer with a known and documented tBRCA mutation. Completed prior standard therapy for curative intent including all of the following, if indicated: neoadjuvant treatment, surgery, adjuvant radiotherapy, and adjuvant chemotherapy. Participants with HR+ breast cancer must be on a stable regimen of endocrine therapy, if indicated, for at least 3 months prior to enrollment. Ovarian suppression, if indicated, must also have been started at least 3 months prior to enrollment. Detectable ctDNA as measured by central Signatera testing. An archival tumor tissue specimen of the primary tumor sufficient in quality and quantity for ctDNA assay design and tBRCA and Homologous recombination deficiency (HRD).  Exclusion Criteria:  Prior treatment with a Poly Adenosine-diphosphate Ribose Polymerase (PARP) inhibitor. Current treatment with a Cyclin-dependent kinase (CDK)4/6 inhibitor or endocrine therapy other than anastrozole, letrozole, exemestane, and tamoxifen. Participants have any sign of metastasis or local recurrence after comprehensive assessment conducted per protocol. Participants have shown no definitive response to preoperative chemotherapy by pathologic or radiographic evaluation, in cases where preoperative chemotherapy was administered. Participants have received live vaccine within 30 days of planned start of study randomization. Participants have a second primary malignancy. Exceptions are the following: (a) Adequately treated non-melanoma skin cancer, curatively treated in situ cancer of the cervix, Ductal carcinoma in situ (DCIS) of the breast, Stage I Grade 1 endometrial carcinoma. (b) Other solid tumors and lymphomas (without bone marrow involvement) diagnosed greater than equal to (>=) 5 years prior to randomization and treated with no evidence of disease recurrence and for whom no more than 1 line of chemotherapy was applied. Participant is pregnant, breastfeeding, or expecting to conceive children while receiving study treatment and/or for up to 180 days after the last dose of study treatment. Participants have a history of human immunodeficiency virus (HIV) disease. Participants have a known history of myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML).