The Response of Chronic Lymphocytic Leukemia to Treatment by Extracorporeal Irradiation of the Blood, Assessed by Isotope-labeling Procedures

The changes in circulating and extravascular lymphocyte pools that followed treatment by extracorporeal irradiation of the blood (ECIB) have been studied by isotopic labeling methods in three patients with chronic lymphocytic leukemia (CLL), each of whom exhibited one of three characteristic patterns of response. The patterns of response, and their interpretations in terms of cell kinetics, were as follows:

A rapid, sustained reduction in circulating leukocytes which occurs when extravascular pools are small in relation to the circulating pool.

A rapid rise in peripheral count after ECIB due to a transfer of cells from the extravascular depots when extravascular pools are relatively large and cellular exchange is slow.

A continuing fall in leukocyte count after ECIB resulting from a differential depletion of proliferating cells when the circulating leukocytes consist both of nonproliferating end cells and of their precursors.

These studies have shown that in planning a treatment schedule it is important to determine the nature of the kinetic processes involved.