18-FLT PET/MR Imaging to Predict Graft Failure and Graft Versus Host Disease in Bone Marrow Transplant Patients
18-FLT PET/MR Imaging to Predict Graft Failure and Graft Versus Host Disease in Bone Marrow Transplant Patients
Allogeneic HSCT is potentially curative for numerous high risk hematologic malignancies and offers several advantages over traditional chemotherapy. First, higher doses of cytotoxic chemotherapy and/or irradiation can be given since patients are subsequently rescued from the severe myelosuppression induced by the pre-transplant conditioning regimen by the infusion of healthy hematopoietic stem cells.
Second and perhaps more importantly, mature T cells contained in the graft are able to mount immune responses against residual cancer cells surviving the conditioning regimen due to major and/or minor MHC disparities between the donor and recipient. Unfortunately, the allo-immune responses driving the GVL effect are typically not specific for malignant cells. As a consequence, donor immune cells attack normal host tissues resulting in a process known as acute graft-versus-host disease (GVHD). Acute GVHD is primarily T cell driven, usually occurs within the first few months after transplant, and results in skin rash, diarrhea, cholestatic liver damage, and, on occasion, acute lung injury.
The current proposal explores the use of a novel imaging modality, FLT PET/MRI, to correlate allogeneic transplant outcomes with FLT and MRI findings during early stem cell engraftment and at a later time point following stable count recovery. Specifically, this study will determine if the strength of the early FLT signal within the bone marrow correlates with engraftment success and if isolated areas of cellular proliferation within the marrow at a later time point might predict for leukemia relapse. In addition, based on the important role that host lymphoid tissues are known to play in GVHD pathogenesis in mice, this study will determine if the FLT signal within host SLT after transplant can predict for the development of GVHD in human BMT patients. Because FLT imaging by itself cannot distinguish between bone marrow engraftment/proliferation and the allo-immune driven T cell expansion that ultimately results in GVHD, this study will image autologous transplant patients as a comparator arm. Autologous HSCT like allogeneic transplantation involves the administration of very high doses of chemotherapy to high risk cancer patients in order to achieve better tumor kill. However, in this situation patients are administered their own cryopreserved stem cells to reconstitute the ablated hematopoietic system. Under those circumstances there is no allo-immune reactivity to drive T cell activation and expansion after transplant, and as a result there is no GVHD in the autologous transplant setting. Thus, these patients will help us to elucidate how much of the FLT signal seen in the allogeneic setting is the result of allo-immune driven T cell expansion.
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