Efficacy and Safety Comparison of Niraparib to Placebo in Participants With Either Human Epidermal Growth Factor 2 Negative (HER2-) Breast Cancer Susceptibility Gene Mutation (BRCAmut) or Triple-Negative Breast Cancer (TNBC) With Molecular Disease (PI: Alina Porojnicu, VV Drammen)

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 ctDNAassay 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).

Contact information: Alina Porojnicu, VV Drammen, alinacp@vestreviken.no