SRT in Combination With Pembrolizumab in Patients With Recurrent Prostate Cancer After Radical Prostatectomy

This study tests whether combining targeted radiation (called salvage radiotherapy) with the immunotherapy drug pembrolizumab improves outcomes for men with prostate cancer that has come back after their prostate was surgically removed. **You may be eligible if...** - You are a male patient, 18 or older - You previously had your prostate surgically removed and your PSA (a blood marker for prostate cancer) has risen again (between 0.2 and 1.0 ng/ml) - Your original prostate cancer was a Gleason score of 7–10 (moderate to aggressive) - You have had recent imaging within the last 50 days **You may NOT be eligible if...** - You still have an undetectable PSA after surgery - Your PSA is higher than 1.0 ng/ml at enrollment - You have plans to father children in the near term (treatment may affect fertility temporarily) - You have certain serious health conditions Talk to your doctor to see if this trial is right for you.