Treatment of chronic lymphocytic leukemia by extracorporeal irradiation.

T HE SENSITIVITY OF LYMPHOCYTES to irradiation provides a rationale for the use of extracorporeal irradiation (ECI ) of the circulating blood to destroy lymphocytes selectively. Since 1962, ECI has been used in various studies, including investigations of lymphocyte physiology and prolongation of allogeneic skin graft survival in calves. These studies1 established the basic feasibility and effectiveness of ECI in reducing the number of circulating lymphocytes and destroying immunologically competent cells. A logical extension of these studies was the application of ECI to treatment of hematologic disorders manifest by increased numbers of abnormal cells in the circulating blood. Theoretical considerations were discussed by Lajtha et al.,2 but their attempts to apply the method to two patients with myeloblastic leukemia were not encouraging. Thomas and co-workers3 reported initial favorable results in four patients with chronic lymphocytic leukemia. In one case of acute lymphoblastic leukemia, temporary reduction of the number of circulating leukemic cells was achieved. Schiffer and co-workers4 reported a similar reduction of the peripheral leukocyte counts in eight patients with acute myelocytic leukemia, two patients with chronic granulocytic leukemia and two patients with chronic lymphocytic leukemia. The present article describes the effects of ECI in six patients with chronic lymphocytic leukemia. The initial course of four of these cases was given previously.3 The subsequent clinical events in these four cases are brought up to date, and two new cases are described.