Reduced Intensity Transplant Using Extracorporeal Photopheresis

Overview

Stem cell transplantation may be used to cure childhood cancers, and other diseases. Traditionally, stem cell transplants use high doses of chemotherapy and radiation. This regimen may cause significant problems after transplant such as infertility, infection, and graft versus host disease (GVHD). Reduced intensity transplant (RIT) uses medications which weaken the immune system, allowing donor cells to take over. The goal of a RIT is to reduce the risk for complications after transplant. Usually medication is used to weaken the immune system, but there are other options such as extracorporeal photopheresis (ECP) that may be less toxic. ECP is currently used for the treatment of GVHD and certain lymphomas. ECP uses a machine that filters white blood cells from the blood, treats them with ultraviolet (UV) light, and then gives all the cells back to the patient. The patient's immune system becomes weaker, allowing the donor cells to replace those of the patient. Studies involving the use of ECP for conditioning have shown fewer side effects than the use of medications. The primary purpose of this clinical research trial is to evaluate the safety and feasibility of ECP as part of a preparative regimen for RIT in children and young adults.

This study tests the feasibility of a reduced intensity preparative regimen for stem cell transplant including extracorporeal photopheresis (ECP), busulfan, and fludarabine in patients with leukemia, lymphoma, and certain non-malignant diseases. The current reduced intensity protocol includes busulfan, fludarabine, and anti-thymocyte immunoglobulin. ECP is currently used in diseases such as chronic GVHD and cutaneous T cell lymphoma. The mechanism of ECP has not been defined. It is hypothesized that exposure of white blood cells to ultraviolet light with 8-methoxypsoralen initiates an apoptotic cellular cascade. Apoptotic cells are recognized and removed by the reticuloendothelial system, initiating the secretion of anti-inflammatory cytokines and the reduction of proinflammatory cytokines. Antigen presenting cells then regulate immune responses through the induction of tolerance. Here we incorporate the use of ECP, fludarabine, and busulfan in the preparative regimen, followed by ECP as prophylaxis for acute graft versus host disease. We hypothesize that photopheresis is safe and feasible, and patients will have similar rates of engraftment with less GVHD as those treated with current reduced intensity protocols. The use of ECP prior to transplant provides immunosuppression promoting host engraftment. Furthermore, the introduction of ECP following transplant may be able to induce tolerance thereby reducing rates of GVHD.