Carmustine Wafer in Combination With Retifanlimab and Radiation With/Without Temozolomide in Subjects With Glioblastoma

This study is testing a new immunotherapy drug called retifanlimab combined with the standard radiation and chemotherapy treatment for people who have just been diagnosed with glioblastoma — the most aggressive type of brain tumor — and already had it surgically removed with chemotherapy wafers (called carmustine wafers) placed in the tumor site. **You may be eligible if...** - You have been newly diagnosed with glioblastoma or a related brain tumor (gliosarcoma) - You already had surgery to remove the tumor, with carmustine wafers placed during that surgery - You have not received any other treatment for your brain tumor - You are 18 or older and have recovered sufficiently from surgery - Your general health is good enough to tolerate chemotherapy and radiation - You are willing to use reliable birth control during the study **You may NOT be eligible if...** - Your brain tumor has come back (recurrent) after prior treatment - You have active autoimmune disease - You have previously received immunotherapy (like PD-1 or CTLA-4 blockers) - You have significant bleeding in the brain on your post-op scan - You are pregnant or breastfeeding - You have another active cancer Talk to your doctor to see if this trial is right for you.