Effect of Splenic Irradiation on Systemic Hematopoiesis

Introduction It has been known since 19031that clinical and hematologic remissions in chronic myelogenous leukemia, a generalized disease, follow irradiation therapy localized to the spleen.2,3The white count will fall and the hemoglobin rises. It has also been apparent that the beneficial effects of irradiation persist for some time after the cessation of therapy.4-5 In an attempt to understand this phenomenon, studies of the sternal bone marrow have been made in these patients following splenic irradiation. Early observers reported contradictory results.5-9In more recent work, a decrease in marrow granulocytic tissue10and a decrease in the number of mitotic figures in the marrow11were observed following splenic irradiation. All of these studies, however, have short-comings in that (1) reliance was placed upon study of bone marrow smears which do not portray accurately the structure of the marrow,12,13and (2) patients were not