Extracorporeal photochemotherapy in the treatment of cutaneous T cell lymphoma and autoimmune disorders affecting the skin.

Extracorporeal photochemotherapy (ECPCT) is a new form of chemoimmunotherapy which involves the ex vivo exposure of malignant peripheral blood cells to 8-methoxypsoralen (8-MOP) and ultraviolet A (UVA) radiation followed by reinfusion of the treated cells. This treatment has resulted in an unprecedented number of prolonged remissions in patients with therapeutically resistant forms of cutaneous T cell lymphoma (CTCL) characterized by the systemic dissemination of a clonal population of malignant helper T lymphocytes. Although the mechanism of the beneficial effect is uncertain, an immune reaction to the reinfused modified T cells probably results in tumour regression. Because the T cell antigen receptor (TCR) is an immunogenic structure and because an identical TCR is present on the entire clonal population of malignant T cells in each individual with CTCL, modification of this structure represents the most likely target for the effects of 8-MOP and UVA. Understanding of the precise events leading to tumour regression in CTCL during treatment with ECPCT may lead to the expanded use of this therapy for other lethal haemopoietic malignancies.