Trimodality Approach of Low Dose iOnizing Radiation With or Without Neoadjuvant Pembrolizumab and Prostatectomy for Men With Intermediate/High Risk Prostate Cancer (TALON)

400 mg of pembrolizumab (KEYTRUDA) will be given by IV every 6 weeks for 9 cycles, for approximately one year of study drug administration.

A single dose of 2 Gy of radiation will be given to the prostate and seminal vesicles on approximately Week 7 for Arm A and approximately 2 weeks prior to the prostatectomy for Arm B.

Robotic assisted laparoscopic prostatectomy (RALP) surgery will be performed at approximately Week 9 for Arm A and approximately 2 weeks after the low dose prostate radiation for Arm B. This surgery is part of the participants routine medical care.