Tamoxifen-associated venous thrombosis and activated protein C resistance due to factor V Leiden

BACKGROUND

Thromboembolic events are well recognized complications of cancers and their treatment. Tamoxifen, an antiestrogen used in the treatment of breast carcinoma and other malignancies, has been associated with thrombotic events. Activated protein C resistance due to Factor V Leiden is the most prevalent inherited prothrombotic defect in populations of European descent and has been reported as a major cofactor in the development of thrombosis in women receiving estrogens.

METHODS

The authors report three patients who developed thromboembolic complications while receiving tamoxifen. These patients were studied for the presence of activated protein C resistance by coagulation assay and the presence of Factor V Leiden by molecular analysis.

RESULTS

All three patients had resistance to activated protein C by coagulation assay and were determined to be heterozygous for Factor V Leiden by molecular analysis.

CONCLUSIONS

The authors propose that inheritance of Factor V Leiden significantly increases the risk of thrombosis in patients who receive tamoxifen therapy. All patients prescribed tamoxifen should be carefully questioned regarding personal and family histories of thrombosis and, when indicated, screened for Factor V Leiden.

Two cases of deep vein thrombosis associated with a combined paroxetine and zotepine therapy

Thromboembolic events arising as a side-effect of neuroleptic and thymoleptic therapy, although rare, represent serious complications. We report on two patients suffering from an acute deep vein thrombosis after administration of a combined therapy with paroxetine and zotepine. The absence of common risk factors for the development of venous thrombosis in both patients led us to reconsider the potential impact that the drugs administered may have on thrombogenesis. Possible influences of the neuroleptic and thymoleptic therapy on the coagulation system are discussed. Although the clinical observations do not necessarily imply a strict causal relationship between drug administration and thrombosis, there are features of these two cases that should enhance our awareness of the possibility of thrombotic events occurring as a consequence of neuroleptic and thymoleptic therapy.

Oral contraceptives and venous thrombosis: different sensitivities to activated protein C in women using second- and third-generation oral contraceptives

Epidemiological studies have shown that women who use third-generation oral contraceptives (OC) containing desogestrel, gestodene or norgestimate have a higher risk of venous thrombosis than women who use second-generation OC containing levonorgestrel. It is also known that a mutation in factor V (factor V(Leiden)), which results in resistance to activated protein C (APC) and which is the most common cause of hereditary thrombophilia, potentiates the prothrombotic effect of OC. Effects of APC on thrombin generation in the plasma of women using OC were compared to the response to APC in non-OC users and in individuals that were heterozygous or homozygous for factor V(Leiden). The response towards APC was evaluated on basis of the ratio (APC-sr) of the time integrals of thrombin formation determined in the presence and absence of APC. Compared with women not using OC, women who used OC exhibited a significantly decreased sensitivity to APC (P<0.001), independent of the kind of OC used. Women who used third-generation monophasic OC were significantly less sensitive to APC than women using second-generation OC (P<0.001) and had APC-sr that did not significantly differ from heterozygous female carriers of factor V(Leiden) who did not use OC. Women who were heterozygous for factor V(Leiden) and used OC had APC-sr in the range of homozygous carriers of factor V(Leiden). Two women who started OC therapy had significantly elevated APC-sr within 3 d. Acquired APC resistance may explain the epidemiological observation of increased risk for venous thrombosis in OC users, especially in women using third-generation OC.

Modeled estimates of myocardial infarction and venous thromboembolic disease in users of second and third generation oral contraceptives

Consistent reports from several recent studies suggest that users of third generation oral contraceptives (OCs) containing gestodene and desogestrel may be at increased risk of venous thromboembolic disease (VTE). Paradoxically, other reports indicate that these users may be at decreased risk of acute myocardial infarction (MI) compared with users of second generation OCs. To determine whether the potentially increased risk of VTE would outweigh the potentially reduced risk of MI in users of third generation OCs, we conducted an analysis to quantify the trade-offs providers and users may be faced to make between these formulations. The baseline rates of VTE and MI among non-users were calculated using US data on incidence and mortality of these conditions and estimates of the proportion of women exposed to these formulations in the US. These were multiplied by relative risks published in recent studies on third generation progestins to produce age- and formulation-specific risks. Results indicate that there would be small differences in disease burden between users of second and third generation OCs under the model assumptions at younger ages. However, among women 35-44 years of age, modeling results indicate that the potentially decreased incidence of MI among users of third generation OCs more than offsets the potentially increased risk of VTE at this age.

[The vascular risk of third generation contraceptive pills]

The new progestative molecules have allowed the reduction of the doses of steroids in estroprogestative pills. They have a reduced androgenic activity allowing the positive effects of ethinylestradiol on lipid metabolism with decreased myocardial infarct, ischemic or hemorrhagic stroke. However it is necessary to consider the woman's entire risk factor profile when prescribing oral contraceptives. Unfortunately, combined estroprogestatives containing low-dose estrogen and the progestagens desogestrel or gestodene are associated with an increased risk for nonfatal venous thromboembolic disease. The occurrence of venous thromboembolic disease in a woman with oral contraceptive requires to search for a hereditary abnormality especially a resistance to the anticoagulant effect of activated protein C. Conversely it seems necessary to screen for the factor V Leiden mutation in women starting oral contraceptives who have a history of a familial venous thrombosis story.

Bias in studies of venous thromboembolism in relation to the use of new formulations of oral contraceptives

The "attrition of susceptibles" was a plausible noncausal hypothesis (that sought to account for the observed association between current use of OCs containing desogestrel or gestodene and the incidence of VTE). However, there are now several pieces of evidence suggesting that this hypothesis can explain, at most, only a small part of the association. For the time being, when weighing the advantages and disadvantages of use of various types of OCs, it is probably prudent to assume that relative to the risk of VTE in users of levonorgestrel, there truly is a heightened risk in women who currently take desogestrel- or gestodene-containing OCs.

Population-based study of risk of venous thromboembolism associated with various oral contraceptives

BACKGROUND

Four studies published since December, 1995, reported that the incidence of venous thromboembolism (VTE) was higher in women who used oral contraceptives (OCs) containing the third-generation progestagens gestodene or desogestrel than in users of OCs containing second-generation progestagens. However, confounding and bias in the design of these studies may have affected the findings. The aim of our study was to re-examine the association between risk of VTE and OC use with a different study design and analysis to avoid some of the bias and confounding of the earlier studies.

METHODS

We used computer records of patients from 143 general practices in the UK. The study was based on the medical records of about 540,000 women born between 1941 and 1981. All women who had a recorded diagnosis of deep-vein thrombosis, venous thrombosis not otherwise specified, or pulmonary embolus during the study period, and who had been treated with an anticoagulant were identified as potential cases of VTE. We did a cohort analysis to estimate and compare incidence of VTE in users of the main OC preparations, and a nested case-control study to calculate the odds ratios of VTE associated with use of different types of OC, after adjustment for potential confounding factors. In the case-control study, we matched cases to controls by exact year of birth, practice, and current use of OCs. We used a multiple logistic regression model that included body-mass index, number of cycles, change in type of OC prescribed within 3 months of the event, previous pregnancy, and concurrent disease.

FINDINGS

85 women met the inclusion criteria for VTE, two of whom were users of progestagen-only OCs. Of the 83 cases of VTE associated with use of combined OCs, 43 were recorded as deep-vein thrombosis, 35 as pulmonary thrombosis, and five as venous thrombosis not otherwise specified. The crude rate of VTE per 10,000 woman-years was 4.10 in current users of any OC, 3.10 in users of second-generation OCs, and 4.96 in users of third-generation preparations. After adjustment for age, the rate ratio of VTE in users of third-generation relative to second-generation OCs was 1.68 (95% CI 1.04-2.75). Logistic regression showed no significant difference in the risk of VTE between users of third-generation and second-generation OCs. Among users of third-generation progestagens, the risk of VTE was higher in users of desogestrel with 20 g ethinyloestradiol than in users of gestodene or desogestrel with 30 g ethinyloestradiol. With all second-generation OCs as the reference, the odds ratios for VTE were 3.49 (1.21-10.12) for desogestrel plus 20 g ethinyloestradiol and 1.18 (0.66-2.17) for the other third-generation progestagens.

INTERPRETATION

The previously reported increase in odds ratio associated with third-generation OCs when compared with second-generation products is likely to have been the result of residual confounding by age. The increased odds ratio associated with products containing 20 micrograms ethinyloestradiol and desogestrel compared with the 30 micrograms product is biologically implausible, and is likely to be the result of preferential prescribing and, thus, confounding.

Increased number of induced abortions in Norway after media coverage of adverse vascular events from the use of third-generation oral contraceptives

After the press release in Lancet (October 18, 1995) of increased risks for adverse vascular events in users of pills containing desogestrel and gestodene the total sales of oral contraceptives dropped over a two-month period by 17%, while sales of the only desogestrel brand available (Marvelon) dropped by over 70% in Norway. From sales, we can estimate that more than 45,000 women either changed from Marvelon to a second or first-generation brand or stopped using OCs. In total, more than 25,000 women discontinued OC use in Norway during November and December of 1995. Abortion data from one Norwegian county, representing 6-7% of the Norwegian population, show no statistically significant changes in the total number of induced abortions from the first quarter of 1996 as compared with that of the first quarter in preceding years. However, abortion rates that had been steadily decreasing from 1992 through 1995 in women 24 years old or younger, were promptly interrupted by a significant 36% increase during the first quarter of 1996. Most of the additional cases were found among single, childless students. The observed increased abortion rate among younger women is most probably linked to changes in contraceptive use during the pill scare of the late October through December of 1995, during which time these women conceived.

[Negative reports on oral contraceptives--increased number of interrupted pregnancies]

The reports on a higher risk of venous thromboembolism associated with third generation oral contraceptives (OCs) received a great deal of media attention in Norway. The Norwegian Medicines Control Authority recommended restricting the use of third generation OCs. The sale of the only third generation OC in Norway decreased by 73%. The total sales of OCs also decreased by 10%, however, despite a recommendation to change drug rather than stop using OC. During the first six months of 1996, the number of legal abortions in 11 hospitals covering 60% of all legal abortions in Norway increased by 297, or 7%, compared with the same period in 1995. A continuous downward trend in the number of legal abortions during the period 1990-95 has been broken, and replaced by an increase, which could represent a greater risk to women's health than a few cases of venous thromboembolism.

Full-thickness burn and venous thrombosis following intravenous infusion of microwave-heated crystalloid fluids

Use of microwave-heated crystalloid fluid has been recommended as one method of correcting hypothermia during resuscitation. We report a case of full-thickness burns and venous thrombosis after microwave-heated crystalloid was infused in the management of a ruptured aortic aneurysm. This case highlights the severity of the burn injury that can occur with infusion of heated fluids. Measuring the temperature of the fluid before the start of the infusion will avoid this complication.

Risk of hospital admission for idiopathic venous thromboembolism among users of postmenopausal oestrogens

BACKGROUND

At the request of researchers in the UK, we conducted a case-control study to explore the relation between use of postmenopausal oestrogen hormone replacement therapy (HRT) and idiopathic venous thromboembolism (VTE).

METHODS

The study was based on information derived from Group Health Cooperative of Puget Sound for the period 1980 to 1994. Women aged 50-74 years admitted to hospital for idiopathic VTE were identified from hospital records. The diagnosis of idiopathic VTE was validated from the clinical record. Women who had medical conditions predisposing to VTE (a history of VTE or cancer, recent trauma, or surgery) were excluded as cases. Four control subjects matched to each case by age, duration of Cooperative membership, and calendar time were identified from the base population. Various potential risk factors were recorded based on record review.

FINDINGS

An initial analysis of 42 cases and 168 matched controls yielded a matched relative risk estimate of 3.6 (95% CI 1.6-7.8) for current users of oestrogens compared with non-users. There was a substantial effect of daily oestrogen dose. The matched relative risk estimates for oestrogen users of 0.325 mg, 0.625 mg, and 1.25 mg or more daily were 2.1, 3.3, and 6.9, respectively. Body-mass index was independently associated with the risk of VTE but did not materially confound the relation of oestrogen and VTE. The absolute risk of idiopathic VTE is estimated to be low (0.9 x 10(-4) woman-years) in non-users of oestrogen; the risk in current users is estimated at 3.2 x 10(-4) woman-years.

INTERPRETATION

The risk of idiopathic VTE is about three times higher among current users of replacement oestrogens than among non-users. However, the absolute risk is low for both groups and accounts for only a modest increase in morbidity.

Prospective study of exogenous hormones and risk of pulmonary embolism in women

BACKGROUND

Current use of oral contraceptives (OCs) is a well-recognised risk factor for venous thrombosis and consequent pulmonary embolism (PE). Little is known about residual effects of past OC use. Furthermore, few epidemiological studies have assessed the relation between postmenopausal use of hormones and thrombotic disease.

METHODS

In this prospective study information was obtained through questionnaires sent every 2 years (1976-92) to 1125,93 women aged 30-55 in 1976. We excluded women with previously diagnosed cardiovascular disease or cancer in 1976 and at the beginning of each subsequent 2-year follow-up period.

FINDINGS

From self-reports and medical records, we documented 123 cases of primary PE (no identified antecedent cancer, trauma, surgery, or immobilisation). Current users of postmenopausal hormones had an increased risk of primary PE (relative risk adjusted for multiple risk factors 2.1 [95% CI 1.2-3.8]). However, past use showed no relation to PE (1.3 [0.7-2.4]). In current users of OCs the risk of primary PE was about twice that in non-users (2.2 [0.8-5.9]), but this finding was based on only five cases who were current OC users. Users of OCs in the past had no increase in risk of PE (0.8 [0.5-1.2]). These relations were consistent irrespective of cigarette-smoking status.

INTERPRETATION

Primary PE was uncommon in this cohort. The risk was increased by current though not past use of postmenopausal hormones or OCs.