The relative frequency of the several types of chronic leukemia and their management

Abstract

One thousand one hundred and seventy-nine cases of leukemia in persons over the age of 13 years seen at the Simpson Memorial Institute of the University of Michigan, from 1927 through 1956, have been reviewed. Seven hundred and thirty-four cases were classified as chronic and 455 as acute. The ratio of acute to chronic cases has shown a steady rise during the period studied so that the incidence of acute leukemia seems to be definitely increasing. The incidence of all forms of chronic leukemia is probably increasing but the nature of the case selection in the present study precludes proof of this thesis. There is no evidence afforded by this series of cases that the relative frequency of chronic granulocytic leukemia and chronic lymphocytic leukemia is changing, or that there has been any change in sex distribution or age incidence in the chronic leukemias. Ionizing radiation continues to be the standard of reference when new forms of treatment for chronic leukemia are proposed, and it has not been conclusively demonstrated that survival times are increased or even equaled by the use of drugs in comparison with x-radiation or radioactive phosphorus. Nevertheless, chemotherapy has largely supplanted radiation in the treatment of chronic granulocytic and lymphocytic leukemias in this institution in recent years. With the passage of time and the enlargement of experience, the use of these therapeutic modalities has received increasing justification. The alkylating agents, Myleran, TEM, and chlorambucil, are the preferred forms of drug therapy for chronic leukemias. There is no evidence of a qualitative difference in biologic actions of these compounds, but there are quantitative variations which affect dosages, absorption rates, duration of effects, and likelihood of severe myeloid depression. At the present time, because of advantages of administration, dosage control, and relative safety, Myleran is generally preferred in chronic granulocytic leukemia and chlorambucil in chronic lymphocytic leukemia. Continuous drug administration on individually determined maintenance dosage has proved superior to intermittent courses of therapy in controlling activity of the leukemic process. Colcemide may be useful in some cases of advanced proliferative granulocytic leukemia and the antimetabolite, 6-mercaptopurine (Purinethol) may be employed in these situations. The adrenal cortical steroids are mainly of value in controlling secondary hemolysis and thrombocytopenia which occur in some patients with chronic lymphocytic leukemia and malignant reticuloendotheliosis. When satisfactory control of these manifestations cannot be established or maintained by hormonal therapy, splenectomy may be effective.