Cyclic Leukocyte Oscillations in Chronic Myelogenous Leukemia During Hydroxyurea Therapy

Cyclic fluctuations of the leukocyte and platelet counts were observed in fivepatients with chronic myelogenous leukemia during treatment with hydroxyurea. The cyclic periods ranged from 30 to 50 days, were similar in eachindividual, but the peak-to-trough values of single cycles varied in magnitude.A second biorhythm was a cyclic undulation of the leukocyte count withheights of the peaks at nine-to-20-month intervals. Rhythmic variations of theplatelet counts were also observed; the period and phase of the cycle beingthe same as that of the leukocyte cycle. No cyclic oscillations were noted inthe hemoglobin or reticulocyte counts. The recognition of the phenomenonmay aid in the use of hydroxyurea or other chemotherapeutic agents in thecontrol of myelogenous leukemia. Chronopharmacology may more accuratelydevelop the use of antitumor agents by its investigation of drug effects onbiologic characteristics as a function of biologic timing.

Submitted on December 19, 1969 Accepted on January 15, 1970