This research study is a Phase II clinical trial. Phase II clinical trials test the safety and effectiveness of an investigational intervention to learn whether the intervention works in treating a specific disease. Investigational means that the intervention is being studied.~How the Study Interventions work:~Pembrolizumab: Pembrolizumab has been studied in lab experiments and in other types of cancer, and information from these studies suggests that it may be beneficial in this type of cancer. Pembrolizumab is a drug (an antibody) that may treat cancer by working with the immune system.~The FDA (the U.S. Food and Drug Administration) has not approved pembrolizumab for this specific disease but it has been approved for other uses.~Radiation (Re-irradiation): Radiotherapy destroys cancer cells using radiation aimed at a cancer from a machine.~The FDA (the U.S. Food and Drug Administration) has approved re-irradiation as a treatment option for this disease.~Bevacizumab: Bevacizumab (also known as Avastin) is designed to prevent or slow down the growth of cancer cells by blocking the growth of blood vessels.~The FDA (the U.S. Food and Drug Administration) has approved bevacizumab as a treatment option for this disease.~In this research study, the investigators are looking to determine if this combination (pembrolizumab + re-irradiation) proves helpful in treating this cancer. If the participant has already been receiving bevacizumab, the participant will continue to receive this along with pembrolizumab and re-irradiation. By doing this, the investigators will look to determine if this combination (pembrolizumab and bevacizumab + re-irradiation) proves helpful in treating this cancer.~This study will also test the safety and tolerability of this combination (pembrolizumab + re-irradiation) when given alone or with bevacizumab
This research study is studying pembrolizumab and re-irradiation as possible treatments for glioblastoma.~The drugs involved in this study are:~Pembrolizumab~Radiation~Bevacizumab, an FDA-approved drug for treating recurrent glioblastoma multiforme (GBM)