A Study of Radiation Therapy With Pembrolizumab and Olaparib or Other Radiosensitizers in Women Who Have Triple-Negative or Hormone-Receptor Positive/Her2 Negative Breast Cancer

Pembrolizumab 200 mg will be administered as a 30 minute IV infusion every 3 weeks for 3 doses

Olaparib will be administered twice daily continuously without breaks on a 21-day (3 week) cycle length, for a total of 2 cycles. Olaparib tablets will be administered bid (2 x 150 mg tablets twice daily; total 600 mg daily) on continuous days without interruption for 2 cycles. Each 3 week period constitutes one cycle.

The dose of radiation will be 8-9 Gy x 3 fractions. Radiation therapy will begin on C1D2-7. For tumors that are too large for this schedule, an accomodation of 30 Gy in 6 Gy per fraction is allowed, a schedule commonly used at MSK.