Study of Olaparib Plus Pembrolizumab Versus Chemotherapy Plus Pembrolizumab After Induction With First-Line Chemotherapy Plus Pembrolizumab in Triple Negative Breast Cancer (TNBC) (MK-7339-009/KEYLYNK-009)

Inclusion Criteria: Induction Period: * Has locally recurrent inoperable TNBC that has not previously been treated with chemotherapy and that cannot be treated with curative intent OR has metastatic TNBC that has not been previously treated with chemotherapy * Has been treated with anthracycline and/or a taxane in the neoadjuvant/adjuvant setting, if they received systemic treatment in the neoadjuvant/adjuvant setting, unless anthracycline and/or taxane was contraindicated or not considered the best treatment option for the participant in the opinion of the treating physician * Has measurable disease based on RECIST 1.1 * Has provided a recently obtained or archival (no more than 3 years old) core or excisional biopsy of a tumor lesion not previously irradiated * Has an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 as assessed within 7 days prior to the start of induction study treatment * Has a life expectancy ≥27 weeks from the day of first study treatment * Demonstrate adequate organ function within 10 days prior to the start of study treatment * A male participant must agree to be abstinent or use contraception and refrain from donating sperm during the intervention period and for at least the time needed to eliminate each study intervention (95 days for olaparib and chemotherapy; no requirement for pembrolizumab) * A female participant must not be pregnant or breastfeeding and must agree to the following if is a woman of childbearing potential …