Trial of Anti-PD-1 Immunotherapy and Stereotactic Radiation in Patients With Recurrent Glioblastoma

This study is testing whether adding an immunotherapy drug (pembrolizumab, which helps the immune system attack cancer) alongside focused radiation therapy can improve outcomes for people with recurrent glioblastoma — a very aggressive form of brain cancer. **You may be eligible if...** - You are 18 or older - You have been diagnosed with WHO Grade IV glioblastoma (GBM) - Your tumor has come back or grown after treatment, and you are planned for surgery and repeat radiation - Your tumor is smaller than 6 cm - You are in good general health (ECOG 0–1) **You may NOT be eligible if...** - You cannot have additional radiation therapy - You have previously received anti-PD-1 or similar immunotherapy - You have an immune system disorder or are on long-term steroids (more than 10 mg prednisone daily) - You have a severe allergy to pembrolizumab Talk to your doctor to see if this trial is right for you.