Extracorporeal photochemotherapy: a scientific overview.

Extracorporeal photochemotherapy was developed for treatment of cutaneous T-cell lymphoma (CTCL). Several independent and multicenter trials using lymphapheresis with 8-methoxypsoralen (8-MOP) activated by shortwave ultraviolet light have demonstrated the clinical benefit of this modality for treatment of advanced CTCL. Recently, trials using the combination of photochemotherapy and recombinant interferons or photochemotherapy and low doses of methotrexate have been initiated to enhance the response to photopheresis. Also, a multicenter study evaluating a new 8-MOP formulation that could be added into the leukocyte/plasma fractions prior to ultraviolet exposure is in progress in CTCL patients. The applications of photochemotherapy in the treatment of other disorders of T-cells are being examined in ongoing clinical trials. Pilot studies have been completed and controlled trials are under way in patients with autoimmune diseases. Important information has emerged regarding the potential use of photopheresis for prevention of solid organ allograft rejection. Several investigators have undertaken pilot studies comparing the efficacy of photochemotherapy with the conventional immunosuppressive therapy for treatment of cardiac transplant rejection. It is hoped that photochemotherapy can induce an immune tolerance in the allograft setting and therefore eliminate or reduce the use of cyclosporin. Other considerations have led to the use of photochemotherapy in the prevention and treatment of graft-versus-host disease after alloeneic and unrelated donor marrow transplantation. Randomized studies are required to evaluate the impact of photochemotherapy on the course of graft-versus-host disease and overall survival.