Graft rejection by a population of primed CDw52- host T cells after in vivo/ex vivo T-depleted bone marrow transplantation

We investigated a case of graft rejection after in vivo/ex vivo T-depleted BMT in a patient who had received a HVG-matched, GVH one locus-mismatched, MLC-negative graft from his cousin. In vivo/ex vivo T cell depletion was performed with Campath 1G (CP1G) and Campath 1M (CP1M), respectively. We identified a failure of CP1G to eradicate a CDw52- (Campath-negative) host T cell population as the main cause of treatment failure. The analysis also suggests that significant host-versus-donor reactivity prior to transplant, as detected by limiting dilution analysis, also contributed to graft rejection. The rejecting T cells were bifunctional in that they showed cytotoxic activity and were capable of inhibiting haemopoietic progenitor growth by producing inhibitory lymphokines.

Pseudoreticulocytosis in a patient with myelodysplasia

A patient with a myelodysplastic syndrome (MDS) and reticulocytosis of > 50% in the absence of a correspondingly increased erythrocyte turnover is reported. Evaluation of the kinetics of erythrocyte turnover revealed a decreased erythrocyte life span of 44 days. From these data a prolongation of the reticulocyte maturation time to > 20 days can be concluded. The patient's erythrocytes lacked the increase of mean corpuscular volume and a significant increase of erythrocyte enzymes that would be expected in marked reticulocytosis. This finding suggests that the reticulocytes represented not newly formed red blood cells, but "pseudoreticulocytes", i.e., mature erythrocytes that retained their substantia reticulofilamentosa.

Interferon in chronic myeloid leukemia. A workshop report

The therapeutic efficacy of interferon-alpha (IFN-alpha) in the treatment of chronic myeloid leukemia is currently being tested in a number of institutional, interinstitutional, and international trials. There is no doubt that responses are achieved in many patients, and in a small subset complete eradication of clonogenic cells may be possible. However, it has not yet been shown that overall survival of patients treated with IFN-alpha is better than that of those treated with conventional cytoreductive drugs. There are still controversial opinions on problems such as dosages and duration of treatment, combination with cytostatic agents, definition of responses, and relevance of cytogenic and molecular data. An international workshop discussed the data on interferon therapy and attempted to define the role of interferon today in the management of chronic myeloid leukemia.

Randomized comparison of busulfan and hydroxyurea in chronic myelogenous leukemia: prolongation of survival by hydroxyurea. The German CML Study Group

In a randomized multicenter study the influence of hydroxyurea versus busulfan on the duration of the chronic phase and on survival of chronic myelogenous leukemia (CML) was determined. In addition cross resistance and adverse reactions of the drugs were analyzed. From July 1983 to January 1991, 441 CML patients were randomized to receive hydroxyurea or busulfan. Of these, 90.7% were Philadelphia positive; 25.7% were low, 38.2% intermediate, and 36.2% high risk patients according to Sokal's score. The median survival of the busulfan treated Philadelphia-positive patients is 45.4 months and of the hydroxyurea group 58.2 months (P = .008). The survival advantage for the hydroxyurea treated patients is recognized in all risk groups. Sixty four patients reached therapy resistance before blast crisis and were crossed over to the alternative drug. The 23 patients with primary hydroxyurea had a median survival of 5.6 years, the 41 patients with primary busulfan therapy a median survival of 2.7 years (P = .02). Adverse reactions were less frequent with hydroxyurea with no severe adverse effects (lung fibrosis, long lasting bone marrow aplasia). The analysis of white blood cell counts in the course of treatment showed lower counts in the hydroxyurea patients. We conclude that hydroxyurea is superior to busulfan in therapy of CML in chronic phase and should be used as first line therapy. Busulfan may have a role as secondary therapy after hydroxyurea resistance or intolerance.

Frequency of bone marrow T cells responding to HLA-identical non-leukemic and leukemic stimulator cells

Grafted immunocompetent cells are considered responsible for GVHD as well as for the elimination of residual leukemic cells ('graft-versus-leukemia reactivity', GVLR) in leukemic patients after allogeneic BMT. Clinical and experimental investigations have given contradictory answers to the question whether GVHD and GVLR are two manifestations of the same process or separate immunologic processes. We have addressed this question by analysing the primary in vitro response of BM-derived proliferating and cytotoxic T lymphocyte precursors (PTLp and CTLp) in HLA identical relative pairs (n = 17). PTLp frequency estimation reveals strong responses (> 1 in 5000) on non-leukemic as well as leukemic stimulation in a majority of cases. CTLp amount variably to 10-100% of the proliferating precursor cells. Preliminary specificity analyses show that on non-leukemic stimulation about 90% of colonies exhibit exclusive lysis of the non-leukemic target. At the same time, on leukemic stimulation, about 75% of cytolytic colonies are exclusively reactive against leukemic targets without crossreactivity against nonleukemic targets from the same patient. Our data show that primary in vitro responses in HLA identical sibling pairs may be as strong as those against allo MHC antigens. In addition CTL specifically lysing leukemic or non-leukemic targets may represent an in vitro model of the immunologic non-identity of GVHD and GVLR.

[Successful treatment of recurrent lower gastrointestinal hemorrhage in intestinal angiodysplasia with an estrogen-progesterone combination]

A 75-year-old man with angiodysplasia of the sigmoid and rectum and recurrent lower gastrointestinal bleeding episodes, despite repeated endoscopic laser-coagulation, was successfully treated with oestrogen-progesterone. Besides angiodysplasia he had aortic valvular stenosis, monoclonal gammopathy, mild renal insufficiency, and moderate peripheral arteriosclerosis obliterans. Oestrogen-progesterone may be a valuable alternative therapy in elderly patients with repeated bleeding, despite endoscopic coagulation, secondary to gastrointestinal angiodysplasia which cannot be treated surgically, in patients who deny surgery, or with rebleeding after surgery.

Influence of graft-versus-host disease on the eradication of minimal residual leukemia detected by polymerase chain reaction in chronic myeloid leukemia patients after bone marrow transplantation

To evaluate the remission quality of Philadelphia chromosome (Ph)-positive, BCR/ABL-positive CML patients after allogeneic bone marrow transplantation (BMT) we used the polymerase chain reaction (PCR) to detect BCR-ABL specific RNA in addition to Southern blotting, cytogenetic, and hematological investigation. Fifty-five bone marrow samples of 27 patients in clinical remission were studied by PCR, 0.5 to 99 months (median 8 months) after BMT. The median clinical follow-up of this cohort of patients is 24 months (1-109) after BMT. BCR-ABL transcripts could be detected in 16 out of 27 patients (59%). Risk factors for minimal residual leukemia (MRD) as defined by PCR were the kind of graft-versus-host disease (GvHD) prophylaxis (patients with T-cell-depleted grafts had a higher rate of MRD in comparison to patients treated with methotrexate/cyclosporin A) and the presence or absence of GvHD after BMT (patients without GvHD had a higher incidence of MRD than patients with GvHD). Moreover, the detection of minimal residual leukemia had prognostic significance. Out of 16 patients with minimal residual leukemia as detected by PCR, four patients relapsed clinically and two further cases relapsed cytogenetically. In contrast none of the patients lacking evidence of minimal residual leukemia relapsed. Serial PCR analysis may prove helpful in deciding about further therapeutic interventions (e.g. interferon therapy or adoptive immunotherapy) before leukaemic relapse becomes manifest after BMT.

Aggressive chemotherapy combined with G-CSF and maintenance therapy with interleukin-2 for patients with advanced myelodysplastic syndrome, subacute or secondary acute myeloid leukemia--initial results

Aggressive chemotherapy of advanced myelodysplastic syndrome (MDS), acute myeloid leukemia (AML) evolving from MDS, subacute AML and secondary AML has usually been associated with low complete remission (CR) rates, a high incidence of early death, and low disease-free survival. We therefore have initiated a phase-III trial of aggressive chemotherapy consisting of idarubicin, cytosine arabinoside, and VP-16 to improve the CR rate. Each chemotherapy cycle is followed by G-CSF to accelerate neutrophil recovery and to reduce the incidence of infections. Until now, 19 patients with high-risk AML have been entered. The CR rate is 47%, with only one death during induction. Patients achieving CR are randomized to receive either high-dose or low-dose interleukin-2 to eliminate residual leukemic cells and to prolong the duration of remission.

Granulocyte-macrophage colony-stimulating factor in the sera of patients with aplastic anemia

To clarify the role of growth factors in the pathophysiology of aplastic anemia we measured serum granulocyte-macrophage colony-stimulating factor (GM-CSF) levels in 33 aplastic anemia patients by a specific and sensitive enzyme-linked immunosorbent assay. GM-CSF serum levels of patients with aplastic anemia were significantly higher than in healthy volunteers. GM-CSF levels were correlated with the severity of aplastic anemia but not with the absolute neutrophil count. Since T lymphocytes are one of the main sources of GM-CSF, our data provide further evidence for in vivo T lymphocyte activation in aplastic anemia. GM-CSF serum levels are higher in patients responding to immunosuppressive treatment than in nonresponders. Elevated serum GM-CSF might be predictive of a good response to immuno-suppressive therapy. GM-CSF serum levels are lower immediately after treatment with antilymphocyte globulin/antithymocyte globulin (ALG/ATG) than corresponding pretreatment values. Thus we cannot confirm the hypothesis that ALG/ATG effects in vivo are mediated by stimulating the release of growth factors. We conclude that in aplastic anemia the primary defect is a failure in GM-CSF response rather than in GM-CSF supply.

Quantitative assessment of posttransplant host-specific interleukin-2-secreting T-helper cell precursors in patients with and without acute graft-versus-host disease after allogeneic HLA-identical sibling bone marrow transplantation

Recent studies in mice and humans have emphasized an important contribution of host-reactive minor histocompatibility antigen (mH)-specific lymphokine-secreting donor T-helper cells (Th) for the induction of acute graft-versus-host disease (GVHD) after allogeneic bone marrow transplantation (BMT). By using limiting dilution (LD) and clonal specificity analyses, we investigated in 14 patients with and without acute GVHD after non-T-depleted HLA-identical sibling BMT whether posttransplant host-reactive mH-specific interleukin-2 (IL-2)-secreting Th are involved in the development of clinically significant acute GVHD and the establishment of tolerance. At different time intervals posttransplant (I, days 0 through 45; II, days 45 through 90; III, days 90 through 180), host-specific IL-2-secreting Th-precursors (Th-p) were quantitatively assessed in six patients during clinically apparent grade II-III acute GVHD. Frequencies of responding Th-p ranged from 1/13,000 to 1 4,000. The presence of host-specific Th-p was significantly correlated with the development of grade II-III acute GVHD (P = .0003 by Fisher's exact test). The detectability of host-specific Th-p preceded the clinical onset of grade II-III acute GVHD. Host-specific Th-p were no longer detectable after the clinical resolution of grade II-III acute GVHD. No subsequent chronic GVHD was observed in these patients. However, prolonged occurrence of host-specific Th-p was accompanied by clinically persisting acute GVHD and the onset of secondary chronic GVHD. In patients with no acute GVHD (grade 0) (n = 7) and grade I (n = 1) acute GVHD, host-specific Th-p were not detectable at all. We conclude that host-reactive Th are critically involved in the development and maintenance of acute GVHD and may contribute to the establishment of tolerance after genotypically HLA-identical sibling BMT.

The German CML study, comparison of busulfan vs. hydroxyurea vs. interferon alpha and establishment of prognostic score 1

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.

Host-specific interleukin-2-secreting donor T-cell precursors as predictors of acute graft-versus-host disease in bone marrow transplantation between HLA-identical siblings

BACKGROUND

Acute graft-versus-host disease (GVHD) is a serious complication of allogeneic bone marrow transplantation from an HLA-identical sibling. There is no practical test before transplantation that gives sufficient information to predict the degree of allogeneic reactivity between HLA-identical siblings.

METHODS

We determined the frequency with which host-specific interleukin-2-secreting donor T-cell precursors occurred in 16 consecutive pairs of HLA-identical siblings before they underwent marrow grafting. The results were correlated with the development of acute GVHD after transplantation.

RESULTS

High frequencies of host-specific T-cell precursors (> or = 1 per 100,000) were detectable before transplantation in eight donors whose siblings later had severe (grade II or III) acute GVHD. Among the donors to eight patients with mild (grade 0 or 1) acute GVHD, low frequencies (< 1 per 100,000) were found.

CONCLUSIONS

Analysis of the frequency of such cells before transplantation may be a useful predictor of severe acute GVHD in allogeneic bone marrow transplantation between HLA-identical siblings. It is possible that the patients at risk for serious acute GVHD after marrow grafting may benefit from some alternative form of immunosuppressive therapy.

[Severe tetraparesis as the first manifestation of a chronic lymphatic leukemia]

Uncertain gait and weakness on standing, progressing to flaccid paraparesis of both legs, developed in a 76-year-old woman. Proprioceptor reflexes of both legs were absent and there was pallaesthesia up to the pelvic rim. Electromyography pointed to polyneuritis. Administration of prednisone, 1 mg/kg daily for 10 days, was ineffective, as was one-time plasmapheresis. An incomplete tetraparesis developed. Blood white-cell count increased within 2 weeks by 10,400/microliters (52% lymphocytes) to 17,400/microliters. Blood smear, bone-marrow cytology and histology, as well as immunocytology, revealed lymphoplasmocytoid immunocytomas (chronic lymphocytic leukemia). Oral cytoreductive treatment was started with chlorambucil, 0.1 mg/kg daily, and prednisone, 100 mg daily. After 19 days the patient was able to walk with support, after 28 was walking unaided. Treatment was continued over eight cycles (14 days' treatment, 14 days' interval per cycle). 17 weeks after onset of treatment paraesthesias of the legs required renewed administration of chlorambucil, 0.1 mg/kg per day, for 3 months. The patient has now been free of symptoms during a follow-up period of 12 months.

Thrombotic thrombocytopenic purpura in early pregnancy with maternal and fetal survival

Thrombotic thrombocytopenic purpura (TTP) is a hematologic disorder which is clinically characterized by thrombocytopenia, microangiopathic hemolytic anemia, fever, neurologic symptoms, and cardiac and renal involvement. The pathogenic mechanisms of this disease are poorly understood. It is well known that TTP is associated with pregnancy and that prognosis for the mother and child is poor. We present the first case of a severe TTP diagnosed in the first trimester of pregnancy (13th week of gestation) with maternal survival and birth of a healthy child which required continuous and intensive treatment with plasma therapy until delivery. During a period of 24 weeks several attempts to discontinue plasma therapy failed because of continuous active disease, and it became evident that plasma infusions were not as effective as plasma exchanges. The fact that the patient entered into remission soon after delivery of a healthy child by cesarean section in the 37th gestational week shows that in this case pregnancy activated an unknown factor which does not cross the placenta and which can be removed by plasmapheresis.

Treatment of aplastic anemia with antilymphocyte globulin and methylprednisolone with or without cyclosporine. The German Aplastic Anemia Study Group

BACKGROUND AND METHODS

Immunosuppression is the most effective treatment for patients with aplastic anemia, except for bone marrow transplantation. The best results are achieved with antilymphocyte globulin or cyclosporine. Patients have been treated successfully with a combination of both agents, but there has been no controlled evaluation of its efficacy. We conducted a randomized, multicenter trial in 84 patients not eligible for bone marrow transplantation, comparing treatment with antilymphocyte globulin and methylprednisolone (41 patients--the control group) with antilymphocyte globulin, methylprednisolone, and cyclosporine (43 patients--the cyclosporine group).

RESULTS

At three months significantly more patients in the cyclosporine group had a complete or partial remission in response to treatment than did patients in the control group (65 percent vs. 39 percent, P less than 0.03); this difference was confirmed at six months (70 percent vs. 46 percent, P less than 0.05). The superior results of the regimen including cyclosporine were most evident in the patients with severe or very severe aplastic anemia, whose response rate at six months was 65 percent, as compared with 31 percent of such patients in the control group (P less than 0.02). Granulocyte and hemoglobin levels became normal in most patients who responded, but platelet counts continued to be subnormal in 61 percent of the patients. Ten of 52 patients with responses (3 in the cyclosporine group and 7 in the control group) relapsed 4 to 37 months after treatment. The actuarial survival of all patients at 41 months is 64 percent in the cyclosporine group and 58 percent in the control group (P = 0.16); among the patients with severe or very severe disease, survival is 80 percent and 44 percent, respectively (P = 0.077). Cyclosporine had substantial but reversible side effects.

CONCLUSIONS

Immunosuppressive treatment of aplastic anemia with antilymphocyte globulin, methylprednisolone, and cyclosporine appears to be more effective than a regimen of antilymphocyte globulin and methylprednisolone without cyclosporine and may thus represent a treatment of choice for patients who are not eligible for bone marrow transplantation.

[Multicenter prospective controlled study of therapy of chronic myeloid leukemia. Comparison of busulfan, hydroxyurea and interferon alpha (April 1990 status)]

In a multicenter study it is being determined, whether the use of hydroxyurea or of interferon alpha instead of busulfan prolongs the chronic phase of Philadelphia-positive CML. Additional goals are the examination, whether the types of disease evolution and the terminal phases differ between the treatment groups, and the prospective recognition of prognostic criteria for the duration of the chronic phase of CML. By September 5, 1990, 593 CML-patients had been randomized, 221 for busulfan, 228 for hydroxyurea and 144 for interferon alpha. The average age is about 51 years. By April 30, 1990, 106 patients had reached the end of the chronic phase, 126 had died. The median survival of Philadelphia-positive patients was 3.95 years, that of all patients 3.75 years. The median observation time of all patients was 1.34 years (mean 1.60 years). At present, no significant difference in survival is recognizable between the three treatment arms, although fewer adverse effects have been observed in the hydroxyurea arm.

Spontaneous interferon-alpha antibodies in a patient with pure red cell aplasia and recurrent cutaneous carcinomas

High-titered spontaneous interferon (IFN) antibodies were detected in a patient with pure red cell aplasia (PRCA), a benign mediastinal tumor, and recurrent cutaneous carcinomas. The circulating IFN antibodies reacted broadly with various human IFN-alpha subtypes (20-140 x 10(3) neutralizing units/ml serum) but not with IFN-beta or IFN-gamma, and they neutralized the antiviral activity of the patient's endogenous IFN-alpha. The IFN-alpha-binding activity was restricted to the IgG1 subclass in a nonmonoclonal manner. Whereas the PRCA repeatedly responded to immunosuppression with high-dose cyclosporin A (CSA) and CSA plus plasmapheresis, IFN antibody production continued during treatment with cyclophosphamide and CSA. Serological analysis revealed past infection with parvovirus B19 and persistent B19 IgM titers. Antibody-mediated impairment of the IFN-alpha system might have favored the development of both PRCA and the various cutaneous carcinomas in this patient.

Functional criteria for staging and treatment of hairy cell leukemia

The determination of clinical stage in hairy cell leukemia is hampered by the lack of common criteria. Furthermore, clinical stages in which the disease should be treated have not yet been defined. In this paper we propose common criteria for the clinical staging of all hairy cell leukemia patients (treated or untreated), as well as for the assessment of responses to therapy. These criteria are absence or presence of disease-related symptoms and disease progression. Based on these criteria we propose that hairy cell leukemia patients in the most favorable stage of the functional system, non-symptomatic Stable Disease (nsSD), do not require treatment. Only in patients with disease-related symptoms and/or signs of disease progression is treatment justified and necessary. No symmetry was observed between the functional stages and Jansen's stages. For evaluation of responses to treatment, our stages were more sensitive than the Leeds criteria. Experimental evidence enables the differentiation of patients with non-symptomatic stable disease from those with symptomatic and/or progressive disease.

In vivo recruitment of GM-CSF-response myelopoietic progenitor cells by interleukin-3 in aplastic anemia

Previous studies have indicated that colony-stimulating factors may stimulate myelopoiesis and thus increase the number of circulating white blood cells in patients with hematopoietic failure including aplastic anemia. However, long-term administration of the factor was required to maintain its response. In the present article we report on a patient with severe aplastic anemia undergoing treatment with recombinant human (rh) granulocyte-macrophage colony-stimulating factor (GM-CSF). After an initial response, the patient became refractory to GM-CSF. However, treatment with interleukin (IL)-3 restored responsiveness to GM-CSF, suggesting that IL-3 may have replenished the bone marrow with myelopoietic progenitor cells sensitive to the action of GM-CSF. This observation suggests the value of application of sequentially acting hematopoietic growth factors in aplastic anemia patients.

Transient pancytopenia. A report from the International Agranulocytosis and Aplastic Study

From a population-based study on the incidence of potentially drug-associated blood dyscrasias 28 cases were identified with pancytopenia. Who recovered within 90 days after diagnosis. Early recovery occurred more frequently in patients showing normal or increased cellularity of the bone marrow than in patients with bone marrow hypoplasia. Median recovery times of leukocytes were 14 and 10 days and of platelets 21 and 9 days in patients with and without bone marrow hypoplasia, respectively. Age and sex distribution were similar in both groups. Of 28 patients, 11 reported a period of fever before onset of pancytopenia. Sixteen patients in whom information on drug use was available had taken a median of 4 drugs before the onset of symptoms that were related to pancytopenia. From these results we present the hypothesis that transient pancytopenia with or without marrow hypoplasia can be the expression of the same type of bone marrow injury and that drugs or viral infections should be considered as etiological factors.

Tumor necrosis factor-alpha, but not lymphotoxin, stimulates growth of tumor cells in hairy cell leukemia

We investigated the effect of recombinant tumor necrosis factor-alpha (rTNF-alpha) and recombinant lymphotoxin (rLT) in the growth modulation of purified hairy cell leukemia (HCL) cells. In response to rTNF-alpha, HCL cells from five of eight patients showed a 3 to 23-fold thymidine incorporation above their unstimulated controls. The effect was time and dose dependent with a maximum between 10 and 25 ng/ml rTNF-alpha after 120-hr incubation. rLT (1-50 ng/ml), however, could not enhance DNA synthesis in six of six cases. Cell number of rTNF-alpha stimulated cells ranged from 2-3 x 10(6)/ml from days 0-50 whereas cell number of unstimulated controls decreased from 3 x 10(6)/ml at day 0 to 0.01-0.02 x 10(6)/ml after 50 days in culture. rTNF-alpha induced proliferation could be suppressed in all HCL cell populations by 0.3 ng/ml recombinant interferon alpha (100 U/ml rIFN-alpha). TNF binding studies in two patients revealed that both TNF-sensitive HCL cells (1,990 +/- 148 receptors/cell) as well as TNF-insensitive HCL cells (1,261 +/- 101 receptors/cell) express specific receptors for TNF-alpha. These data show that rTNF-alpha and rLT have different effects on the growth of HCL cells. In addition there is a subgroup of patients who show no response to rLT or rTNF-alpha.

Idiopathic myelofibrosis: a retrospective study of 103 patients

The clinical course of 103 patients (50 males, 53 females; median age 59 years) with idiopathic myelofibrosis (IMF) seen at our hospital between 1967 and 1986 was analyzed retrospectively. Common symptoms and signs at the time of diagnosis were: myelofibrosis (96%), splenomegaly (84%), anemia (81%), osteosclerosis (45%), malaise (41%) and leukocytosis (41%). It was possible to follow the majority of patients without treatment or with transfusion therapy only for prolonged periods of time. The use of cytostatic drugs and radiotherapy was restricted as much as possible. Probably due to this treatment strategy the incidence of acute leukemia was low (5%). Major thromboembolic complications were seen in 19% of the patients. Median survival of the patients was 4.3 years. The prognostic influence of several disease parameters determined at the time of diagnosis was tested: age, sex, leukocytes, platelets, hemoglobin, reticulocytes, LDH, ANP-score, spleen size and percentage of peripheral blood blasts + promyelocytes had no significant influence on the length of survival. Osteosclerosis, a presumed sign of advanced disease, was not correlated with survival either.