The purpose of the study is to test the safety and effectiveness of the study drug, pembrolizumab (MK-3475) with certain types of chemotherapy and endocrine therapy, as well as, to see how well the subject's body handles the study drug.
If subject's meet the criteria, they will be assigned to 1 of 2 groups by chance, similar to flipping a coin, in order to decide which study treatment they will receive. Group A will receive the study drug, pembrolizumab, with certain types of chemotherapy and endocrine therapy. Group B will receive placebo, with certain types of chemotherapy and endocrine therapy. Pembrolizumab or placebo will be given by vein about once every 3 weeks.
This is a long-term study, if subject's agree to participate, they will be in the study for approximately 12 years.