Cell Cycle Effect of Extracorporeal Irradiation of the Blood in Acute Myeloid Leukaemia

A patient with acute myeloid leukaemia was treated with extracorporeal irradiation of the blood. During the irradiation, the blood blast cell count decreased considerably. Bone marrow studies showed an increase of the 3H-thymidine labelling index and particularly of the mitotic index within 8 hours after start of treatment; possible mechanisms of this are discussed. The rises in indices were moderate, however, and it remains to be seen whether such cytokinetic perturbations are large enough to allow definite therapeutic exploitation.