Effect of Splenic Irradiation on Systemic Hematopoiesis

Introduction  It has been known since 1903¹ that clinical and hematologic remissions in chronic myelogenous leukemia, a generalized disease, follow irradiation therapy localized to the spleen.^2,3 The 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.^4-5In 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.^5-9 In more recent work, a decrease in marrow granulocytic tissue¹⁰ and a decrease in the number of mitotic figures in the marrow¹¹ were 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,^12,13 and (2) patients were not