From July 1983 to January 1991 a total of 622 patients were randomized (585 eligible) to compare the effects of hydroxyurea, interferon alpha (IFN), and busulfan on the duration of chronic phase, and survival. Further goals included the determination of prognostic parameters. 598 CML patients were documented and 575 evaluable. The Ph-status was known for 547 patients. 89.4% of the patients were Ph-positive (+). 11% had additional chromosome aberrations. The median survival of Ph+ patients by now is 4.2 years, that of Ph-patients 1.4 years. Ph-negative patients are older, tend to have lower cell counts and, as a group are more ill at diagnosis. A survival difference of about one year is expected between busulfan and hydroxyurea treated patients. Prospectively evaluated age, organomegaly related symptoms, Karnofsky index, extramedullary manifestations, number of erythroblasts and percent of circulating blasts proved to be of prognostic significance. A prognostic score (score 1) was determined which was superior to Sokal's score in the study population. 164 patients were randomized to receive IFN. In 54 patients (33%) IFN had to be terminated because of adverse effects, therapy resistance or other reasons. Clinically relevant neutralizing antibodies were detected in 9 cases. Most frequent adverse events were flu-like symptoms in 74%, gastrointestinal symptoms in 52%, and neurologic-psychiatric symptoms in 30% of patients. Reduction of the Ph-chromosome was observed in 13% of evaluable patients (10 of 75). In 4 patients complete cytogenetic remissions were observed, in three of these ongoing. Cytogenetic responders have a survival advantage. Interferon treated Philadelphia-negative CML patients have no survival disadvantage. The study is expected to allow statements as to the advantages or disadvantages of the use of busulfan, hydroxyurea and IFN in the treatment of CML as well as to the reliability of prognostic markers.

Summary. Polyploidization of human megakaryocytes was studied in bone marrow aspirates from three normal individuals, three patients with idiopathic thrombocytopenic purpura (ITP) and three patients with pernicious anaemia (PA). The cells were labelled in vitro with tritiated thymidine and analysed by a combined cytophotometric and autoradiographic method. Cells were divided into types I, II and III. Normal megakaryocytes showed ploidy stages from 4c to 32c, the 4c stage occurring only in type I. The labelling indices showed that in normal megakaryocytes polyploidization takes place in type I and II and not in type III cells. This study provided evidence for alternation of DNA synthesis and rest periods. It is postulated that rhythmical polyploidization in megakaryocytopoiesis takes place. The progressive increase in the proportion of cells in successive resting periods (G‐phases) suggests that high ploidy cells have longer resting periods than low ploidy cells. In ITP, megakaryocyte morphology, labelling indices and distribution of DNA content were normal. Assuming a normal ploidy composition in ITP, the megakaryocytic hyperplasia observed in typical cases may be explained by an increased influx from the unrecognizable progenitor cell. In PA, an arrest of megakaryocytic DNA synthesis was observed comparable to that found in megaloblastic erythropoiesis.

In 7 cases of untreated and 2 cases of treated acute leukaemia (AL) the erythropoietic cell proliferation was studied by the combined method using AFeulgen-cytophotometry and autoradiography after labelling with 3H-TdR in vivo (1 h after intravenous injection) or in vitro. A proliferation disturbance was observed, which was almost limited to the early polychromatic erythroblasts, consisting of an accumulation of diploid and unlabelled cells and a decreased proportion of cells in S. This proliferation defect was not present during complete remission. The results indicate the existence of out-of-cycle cells (G0-cells) in the erythroblasts of AL, which may be responsible for ineffective erythropoiesis in this disease.

In a 13-year-old patient with acute leukaemia the leukaemic blast cells, the nucleated red cells and the megakaryocytes were studied by cytophotometrie determination of the DNA content and autoradiographic labelling with ³H-TdR invitro. In the preleukaemic phase a striking proliferation defect in the early polychromatic erythroblasts was observed, consisting of an accumulation of cells in G₁ and a decreased proportion of cells in S. In the megakaryocytes low DNA values from 2c-8c as compared to 4c-32c in normal megakaryocytopoiesis, and a decreased number of labelled cells between the ploidy stages was observed, indicating a severely restricted polyploidization capacity. These results suggest that in the preleukaemic stage a basic proliferation defect of acute leukaemic is becoming apparent in the so-called non-leukaemic cell systems, leading to peripheral mono- or pancytopenia.