Reduced Intensity Conditioning Allogeneic Hematopoietic Stem Cell Transplant (HSCT) For Lymphoma

This research study is a Pilot Study, which is the first time investigators are examining this study intervention (allogeneic stem cell transplantation) for this population (patients with CNS lymphoma), which is a type of stem cell transplantation. Historically, patients with central nervous system (CNS) involvement by non-Hodgkin lymphoma (NHL) have had high rates of disease relapse after initial therapy. Given these poor outcomes with conventional chemotherapy, more intense treatment with high-dose chemotherapy and autologous stem cell transplantation (ASCT) has been explored, yet relapse remains an issue. For older patients, ASCT may not be feasible given the inability to tolerate high-doses of chemotherapy. In patients with systemic NHL who relapse after ASCT or cannot tolerate ASCT, yet are responsive to chemotherapy, allogeneic stem cell transplant is often considered. Allogeneic transplantation is thought to work by giving the recipient an entirely new blood system from a donor. This new blood system includes a new immune system which can hopefully attack any lymphoma much like it would attack a bacterial or viral infection. Currently, this is one established standard of care for patients with lymphoma of the body who relapse after initial chemotherapy treatment. The investigators are testing if this treatment can be extended to patients with lymphoma of the central nervous system. The following chemotherapy drugs included in this study which will be administered: Fludarabine, Thiotepa, and Methotrexate. The FDA (the U.S. Food and Drug Administration) has approved these chemotherapy agents individually as a treatment option for your disease. The combination has not been approved by the FDA. Thiotepa and Methotrexate have been shown to pass through the blood-brain barrier, a highly selective barrier that restricts many chemicals from entering the brain and spinal cord. Fludarabine is the backbone chemotherapy in all reduced intensity conditioning regimens.