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ABSTRACT: The magnitude of the relative risk of venous thrombosis caused by low-dose oral contraceptive use is still debated because previous studies might have been affected by diagnostic suspicion and referral bias.
We conducted a case-control study in which the effect of diagnostic suspicion and referral bias was excluded. The study was performed in 2 diagnostic centers to which patients with clinically suspected deep vein thrombosis of the leg were referred. History of oral contraceptive use was obtained before objective testing for thrombosis. Young females with an objective diagnosis of deep vein thrombosis were considered case patients, and those who were referred with the same clinical suspicion but who had no thrombosis served as control subjects. Participants were seen between September 1, 1982, and October 18, 1995: 185 consecutive patients and 591 controls aged 15 to 49 years with a first episode of venous thrombosis and without malignant neoplasms, pregnancy, or known inherited clotting defects.
The overall odds ratio for oral contraceptive use was 3.2 (95% confidence interval [CI], 2.3-4.5); after adjustment for age, family history of venous thrombosis, calendar time, and center, the odds ratio was 3.9 (95% CI, 2.6-5.7). In the idiopathic group (120 patients and 413 controls, excluding recent surgery, trauma, or immobilization), the odds ratio for oral contraceptive use was 3.8 (95% CI, 2.5-5.9); after adjustment, the odds ratio was 5.0 (95% CI, 3.1-8.2).
In this study, in which patients and controls were subj ect to the same referral and diagnostic procedures, we found similar relative risk estimates for oral contraceptive use as in previous studies. We conclude that diagnostic suspicion and referral bias did not play an important role in previous studies and that the risk of venous thrombosis with use of current brands of oral contraceptives still exists.
Archives of Internal Medicine 02/1999; 159(1):65-70. · 11.46 Impact Factor
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ABSTRACT: A deficiency of protein C (PC), antithrombin, or protein S is strongly associated with deep-vein thrombosis in selected patients and their families. However, the strength of the association with venous thrombosis in the general population is unknown. This study was a population-based, patient-control study of 474 consecutive outpatients, aged less than 70 years, with a first, objectively diagnosed, episode of venous thrombosis and without an underlying malignant disease, and 474 healthy controls who matched for age and sex. Relative risks were estimated as matched odds ratios. Based on a single measurement, there were 22 (4.6%) patients with a PC deficiency (PC activity, less than 0.67 U/mL or PC antigen, less than 0.33 U/mL when using coumarins). Among the controls, the frequency was 1.5% (seven subjects). Thus, there is a threefold increase in risk of thrombosis in subjects with PC levels below 0.67 or 0.33 U/mL [matched odds ratio, 3.1; 95% confidence interval (CI), 1.4 to 7.0]. When a PC deficiency was based on two repeated measurements, the relative risk for thrombosis increased to 3.8 (95% CI, 1.3 to 10); when it was based on DNA-confirmation, the relative risk increased further to 6.5 (95% CI, 1.8 to 24). In addition, there was a gradient in thrombosis risk, according to PC levels. The results for antithrombin are similar to those for PC, although less pronounced (relative risk, 2.2; 95% CI, 1.0 to 4.7). We could not find an association between reduced total protein S (relative risk, 0.7; 95% CI, 0.3 to 1.8) or free protein S levels (relative risk, 1.6; 95% CI, 0.6 to 4.0) and thrombosis risk. Although not very frequent, PC and antithrombin deficiency are clearly associated with an increase in thrombosis risk.
Blood 06/1995; 85(10):2756-61. · 9.90 Impact Factor
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ABSTRACT: The role of the complement system in the pathogenesis of pulmonary leukostasis in myelocytic leukemia was studied in a rat model. Acute myelocytic leukemia was induced in six Brown-Norway rats, and complement levels were assayed during the course of the disease. Whole complement activity (CH50) and hemolytic activity of C1q, C3, and C4 decreased from day 16 after induction of the leukemia, when the rats developed pulmonary leukostasis. In addition, local complement activation was established in the lung vessels by immunofluorescence microscopy in advanced stages of pulmonary leukostasis. Finally, following systemic activation of the complement system by injection of cobra venom factor (CVF), leukemic rats (n = 6) died of pulmonary leukostasis 4.5 days earlier than did leukemic controls (n = 6). These findings suggest that, in acute myelocytic leukemia in Brown-Norway rats, pulmonary leukostasis is induced by activation of the complement system. This finding could lead to new modes of treatment for a life-threatening complication of leukemia.
Leukemia 11/1993; 7(10):1608-14. · 9.56 Impact Factor
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ABSTRACT: In this study the hypothesis that inhibition of the de novo pathway results in stimulation of salvage pathway activity was tested. The key enzyme in the balance between these two pathways is ribonucleotide reductase (RR), which can be inhibited by hydroxyurea (HU). The metabolism of 1-beta-D-arabinofuranosylcytosine and 5-Aza-2 deoxycytidine (Aza-dC), which are activated via the salvage pathway, was evaluated in cells from Ara-C-sensitive and -resistant myelocytic leukemia cell line (BNML-Cl/0 and BNML-Cl/Ara-C). The combination of HU and Ara-C caused as much as a threefold increase of Ara-CTP; it significantly increased the incorporation of Ara-C into DNA and induced synergistic cytotoxicity, as evaluated in a colony assay. Even in the deoxycytidine (CdR) kinase-deficient Ara-C-resistant cell line, HU was partially able to restore sensitivity to Ara-C and Aza-dC. dCTP levels are reduced during the first 10 h after incubation with HU, but this effect vanishes at the time when phosphorylation is maximal. Increased CdR kinase activity in cell-free extracts could explain the enhanced synthetic salvage pathway activity, which is likely due to the fact that more enzyme is present (Vmax has increased by Km unchanged). RR inhibition combined with Ara-C might provide a means of eliminating leukemic cells with suboptimal anabolic salvage pathway activity, which otherwise survive Ara-C chemotherapy.
Annals of Hematology 08/1992; 65(1):26-32. · 2.62 Impact Factor
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ABSTRACT: The pathogenesis of pulmonary leukostasis in leukemia was studied in a rat model by investigating the course of its development. Leukemia was induced by inoculating rats with leukemic cells. The earliest stage of leukostasis was found from day 14 onward, when leukemic cells appeared in the peripheral blood, and was characterized by accumulation of leukemic cells at the capillary level. Simultaneous with the increase of leukemic cell concentrations in the peripheral blood, accumulation in capillaries increased gradually over a period of several days. This was accompanied by increasing severity of tachypnea. Shortly before death, aggregates consisting almost solely of leukemic cells were found in medium-sized blood vessels. This stage was rapidly followed by the end-stage, characterized by complete obstruction of the lung vasculature--including the largest arteries and veins--by leukemic cell aggregates, giving rise to extensive hemorrhages and edema. The end-stage was considered to be the cause of death, which occurred 18-26 days after the inoculation. The histological and ultrastructural findings in this study suggest that besides the size and stiffness of individual leukemic cells, interactions not only between leukemic cells, but also between leukemic cells and the endothelium play a role in the pathogenesis of pulmonary leukostasis.
Leukemia 03/1992; 6(2):142-9. · 9.56 Impact Factor
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ABSTRACT: In the present study we demonstrate that Aza-dC in combination with Amsacrine has major antileukaemic properties in patients who have not already received extensive Ara-C therapy. Eight out of 11 patients in their first relapse of acute leukaemia achieved complete remission. Cross resistance between Ara-C and Aza-dC was revealed by the lack of antileukaemic activity in five patients with with Ara-C resistant leukaemia. Combination therapy with Aza-dC/Ams-acrine induced a considerable period of a granulocytopenia (28-35 days), while the toxic effect on erythro- and megakaryopoiesis was comparable to that reported for high dose Ara-C/Amsacrine chemotherapy. Remarkable is the long disappearance time for leukaemic blast cells in bone marrow, i.e. 3-5 weeks in some cases. Analysis of cell membrane markers showed a loss of the early differentiation antigens CD34 and CD33 from leukaemic bone marrow cells after 7 days of Aza-dC treatment, which is suggestive of leukaemic cell differentiation. In the small group of patients tested for DNA hypomethylation no association existed between the degree of hypomethylation and clinical response. Non-haematologic side effects were considerable in patients receiving the highest dosages of Aza-dC and consisted of severe, although usually reversible, gastrointestinal and neurological complications. In comparison with Ara-C, Aza-dC causes less nausea and vomiting and is therefore better tolerated.
British Journal of Cancer 08/1991; 64(1):144-8. · 5.04 Impact Factor
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American Journal Of Pathology 04/1991; 138(3):777-80. · 4.89 Impact Factor
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ABSTRACT: In this study we describe the establishment of a leukemic cell line (BNML-CL/ara-C), originating from the 1-beta-D-arabinofuranosylcytosine (ara-C)-resistant brown Norway rat myelocytic leukemia model (BNML/ara-C), that retains the in vivo generated ara-C resistance. Its biological and biochemical characteristics have been compared with a cell line, derived from the ara-C-sensitive BNML model (BNML-CL/O). Resistance to ara-C was attributed to a decrease in phosphorylation of ara-C. Deoxycytidine (dCyd) kinase activity in crude cell extracts with dCyd as substrate showed similar enzyme activities in both cell lines, whereas with ara-C as substrate no dCyd kinase activity was detectable in the ara-C-resistant cell line. Two isoenzymes of dCyd kinase with different substrate specificities have been described (Cheng, Y.C., Domin, B., and Lee, L.S. Biochim. Biophys. Acta, 481: 481-492, 1977), cytoplasmic (dCyd kinase I, substrates: dCyd and ara-C) and mitochondrial (dCyd kinase II, substrates: dCyd and thymidine). In the ara-C-sensitive BNML model, thymidine induced a reduction of dCyd kinase activity when dCyd was used as substrate. However, thymidine did not affect kinase activity with ara-C was used as substrate. In the BNML-CL/ara-C, thymidine even induces a dCyd kinase inhibition of 85% with dCyd as substrate. It is likely that the ara-C-specific dCyd kinase deficiency in BNML-CL/ara-C cells was due to a selective loss of dCyd kinase I, whereas dCyd kinase II activity remained intact.
Cancer Research 11/1990; 50(20):6515-9. · 7.86 Impact Factor
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ABSTRACT: In this study 10 patients with acute myelocytic leukemia (AML) each received a rapid intravenous injection of high dose cytosine arabinoside (HD Ara-C; 1 g/m2). Bone marrow aspirates were obtained before and after Ara-C administration to determine the percentage of cells in S-phase measured by flow cytometry. In 5 out of 10 cases synchronization of the leukemic cells in S-phase of the cell cycle was observed. However, the time of maximum synchronization turned out to be difficult to predict. Therefore, the strong correlation between percentage of cells in S-phase at diagnosis and the time of maximal accumulation of S-phase cells after Ara-C administration, as observed by others in childhood AML, could not be confirmed for adult AML patients. Although synchronization of AML cells after in vivo Ara-C administration could be demonstrated in at least half of the patients, the practical consequences are such that clinical application was hampered.
Blut 03/1990; 60(2):76-80.
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ABSTRACT: In this study we investigated the Ara-CTP-forming capacity of leukemic cells in different phases of the cell cycle. Cells from two leukemic cell lines and leukemic bone marrow cells from patients and rats (BNML model) with acute myelocytic leukemia were separated according to cell cycle phase by means of an albumin density gradient in a specially designed sedimentation chamber. We found that the activity of CdR kinase and Cyt deaminase is much less influenced by cell-cycle phase progression than TdR kinase activity. For the leukemic cell lines HL-60 and BNML-CL/O CdR kinase activity is even independent of cell-cycle phase. In addition, Ara-CTP formation is not restricted to cells in S-phase. Cell cycle phase-independent Ara-CTP formation creates a situation in which cells which are not in S-phase during exposure to Ara-C might undergo the cytotoxic effects of Ara-C as soon as they enter S-phase.
Leukemia Research 02/1990; 14(4):363-9. · 2.92 Impact Factor
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Bone Marrow Transplantation 01/1990; 4 Suppl 3:64. · 3.75 Impact Factor
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ABSTRACT: Using a Brown Norway rat leukaemia model (BNML), which is a realistic model of human myelocytic leukaemia, we compared the antileukaemic activity, influence on cell cycle kinetics and effect on normal haematopoiesis of 5 aza-2-deoxycytidine (aza-dC) and arabinofuranosyl-cytosine (ara-C). The antileukaemic activity was evaluated by means of a survival study. For aza-dC a dose-response relationship was demonstrated for doses up to 50 mg kg-1 (3 times q 12 h); a higher dose resulted in only a slight increase in median survival time (MST). For ara-C a weak dose-response relationship was observed. At the maximum dose of aza-dC and ara-C tested, aza-dC induced a 10-day longer survival time than ara-C, which means 2 logs more of leukaemic cell kill for aza-dC. By means of flow cytometric analysis and a 3HTdR uptake study it was shown that aza-dC does not influence the cell cycle kinetics in the first 24 h after exposure, in contrast to ara-C which caused the characteristic G1/S blockage and synchronization. The influence of aza-dC and ara-C on normal haematopoiesis was evaluated with the CFU-S assay. The dose-response curve for CFU-S did not show a significant difference in stem cell cytotoxicity between aza-dC and ara-C. In the BNML model aza-dC is a much more effective antileukaemic agent than ara-C, while the toxic effect on normal haematopoiesis is comparable to that of ara-C.
British Journal of Cancer 01/1989; 58(6):730-3. · 5.04 Impact Factor
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ABSTRACT: Increased dosages of cytosine arabinoside (Ara-C) have been shown to be active in remission induction and consolidation treatment of patients with primary refractory acute lymphoblastic leukemia (ALL) and lymphoblastic non-Hodgkin's lymphoma (lyNHL). From August 1983 to December 1986 we treated 25 patients with ALL (9) and lyNHL, stage III and IV (16), median age 22 (range 15-48 yr) with a protocol consisting of remission induction with vincristine, prednisone, adriamycine and Ara-C (1 g/m2 twice daily as 2-h infusion d1-6) and intrathecal methotrexate, followed by consolidation courses with vincristine, prednisone, adriamycine and Ara-C (3 g/m2, twice daily as 2-h infusion d1-4) and intrathecal methotrexate. Some patients received CNS and/or mediastinal irradiation. No maintenance was given. 18 patients (72%) achieved complete remission (5 of the 11 previously treated and 13 of the 14 previously untreated patients). Consolidation courses were given to 17 patients. 5 of them relapsed in the bone marrow (3), skin (1) and CNS plus bone marrow (1) at 5, 5, 6, 6 and 24 months. The duration of complete remission ranged from 5 to 51+ months; the median could not yet be calculated. Short-term intensive treatment might be a worthwhile approach for ALL and lyNHL.
European Journal Of Haematology 12/1988; 41(5):489-95. · 2.61 Impact Factor
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ABSTRACT: Seventy-two adults were treated for acute myelogenous leukaemia (AML). Forty-two had previously untreated AML and 30 had AML after a preleukaemic phase, refractory AML or relapsed AML. The previously untreated patients received a 7-day course of cytosine arabinoside (100 or 200 mg/m2 daily), daunorubicin and vincristine while the remaining patients received a 7-day course of cytosine-arabinoside (1 g/m2 q 12h for 6 days) and amsacrine (on day 7). The percentage of malignant cells and the reduction in the percentage of malignant cells were determined by means of bone marrow aspirates taken on day 6 of the chemotherapy course and at the time of diagnosis. Both variables correlated significantly with the ultimate treatment outcome; the reduction in the percentage of malignant cells correlated even more significantly than the absolute percentage malignant cells in the day-6 bone marrow. By means of multiple regression analysis it became possible to calculate the probability of achieving complete remission for the individual patient; this is given by the equation: probability = 1.9-0.009X (% malignant cell reduction). In addition, the mean percentage of malignant cells in the day-6 bone marrow was significantly higher for patients who failed to achieve than those who entered complete remission. Eighty-six per cent of the patients with less than 20% malignant cells on day 6 entered remission, while 75% of the patients with more than 21% malignant cells failed to achieve complete remission (p less than 0.001). Although all of these calculations support the predictive value of the day-6 bone marrow aspirate, the 95% confidence intervals are too large to allow reliable and safe predictions; therefore more patients must be studied to demonstrate the reliability of this test.
Blut 09/1988; 57(2):91-5.
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ABSTRACT: 50 patients (aged 18-58 years) with acute myelogenous leukaemia after a preleukaemic phase (n = 14), acute myelogenous leukaemia that previously failed to respond to conventional chemotherapy (n = 9) or relapsed disease (n = 27) were given remission induction therapy consisting of cytosine arabinoside (1 g/m2 q 12 h x 12) and m-Amsa (115 mg/m2 for 1 or 3 days). Overall, 27 patients (54%) achieved complete remission. The complete remission rate for patients with acute myelogenous leukaemia after a preleukaemic phase (7/14) and those with primary refractory or relapsed leukaemia (20/36) seems superior to that obtained with conventional remission-induction therapy. 12 patients received 1-3 courses of consolidation chemotherapy with cytosine arabinoside (3 g/m2 q 12 h x 8) and m-Amsa (115 mg/m2 for 1 d). 3 of them subsequently underwent autologous bone marrow transplantation. The median duration of remission for the remaining 9 patients was 8 months. 11 patients did not receive consolidation therapy; their median duration of remission was 3 months. The difference between the two groups was not significant. 4 patients underwent allogeneic bone marrow transplantation after achievement of complete remission. The impact of high-dose cytosine arabinoside consolidation chemotherapy on poor-risk acute myelogenous leukaemia remains unclear.
European Journal Of Haematology 04/1988; 40(3):198-204. · 2.61 Impact Factor
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Blut 02/1988; 56(1):1-11.
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Seminars in Oncology 07/1987; 14(2 Suppl 1):86-91. · 3.50 Impact Factor
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ABSTRACT: In this study, it has been shown that in 21 patients with AML the dCyd kinase and dCyd deaminase activities correspond closely to the clinical response to ara-C remission induction therapy. Patients with primary disease were treated with a conventional-dose ara-C regimen whereas nonresponders and relapsed patients followed an ID ara-C regimen (1 g/m2 X 12). Of these 21 patients (11 with primary disease and ten relapsed), seven had ara-C resistant disease (three primary and four relapsed patients). Five of the seven patients had a very low dCyd kinase and normal dCyd deaminase activity, whereas the other two had a normal dCyd kinase and an increased dCyd deaminase activity.
Seminars in Oncology 07/1987; 14(2 Suppl 1):257-61. · 3.50 Impact Factor
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British Journal of Haematology 05/1987; 65(4):501-2. · 4.94 Impact Factor
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ABSTRACT: High-dose Ara-C consolidation therapy for patients with primary refractory or relapsed acute leukemia (AML and ALL) or relapsed lymphoblastic non-Hodgkin's lymphoma (LNHL) was investigated. Between January 1983 and January 1986, 47 adult patients with primary refractory or relapsed AML, ALL or lymphoblastic NHL received a remission induction regimen that included intermediate-dose Ara-C (lg/m2/2hr q 12hr X 12). Of the twenty-nine (61.7%) patients who achieved complete remission sixteen (AML 9, ALL 5, LNHL 2) received 1-3 consolidation courses that included high-dose Ara-C (3g/m2/2hr q 12hr X 8). Three patients died as a result of major infections during the pancytopenic phase that followed the first consolidation course and 6 relapsed at 4, 4, 6, 8, 9 and 16 months; at the moment of this report the remaining 7 patients have been in continued remission for 8 to 28 months (6 have been in continued complete remission for greater than or equal to 11 months). The predicted median disease-free interval for patients who survived consolidation therapy is 16 months. Of the 13 patients who did not undergo consolidation chemotherapy 2 subsequently underwent allogeneic bone marrow transplantation and 3 died as a result of major infectious complications while in complete remission. Eight patients received no further treatment because they refused or had previously experienced severe toxicity. The median disease-free interval for this group was only 3 months. Our preliminary data on brief intensive consolidation therapy for patients with relapsed or primary refractory leukemia or non-Hodgkin's lymphoma suggest that this kind of treatment prolongs disease-free interval.
European Journal of Cancer and Clinical Oncology 05/1987; 23(4):401-5.
