Used primarily in chemotherapy to treat brain tumors such as glioblastoma multiforme, glioma, and medulloblastoma. Also employed in the treatment of Hodgkin's and non-Hodgkin's lymphoma, as well as multiple myeloma. Delivered intravenously or as an implantable wafer during brain surgery to provide localized treatment. Its ability to cross the blood-brain barrier makes it particularly effective for central nervous system cancers. Often part of conditioning regimens before bone marrow or stem cell transplantation due to its immunosuppressive properties.