Fatal myocardial infarction in the Scottish adjuvant tamoxifen trial. The Scottish Breast Cancer Committee

Sex and sex steroids as determinants of cardiovascular risk

There are considerable sex differences regarding the risk of cardiovascular disease (CVD), including arterial hypertension, coronary artery disease (CAD) and stroke, as well as chronic renal disease. Women are largely protected from these conditions prior to menopause, and the risk increases following cessation of endogenous estrogen production or after surgical menopause. Cardiovascular diseases in women generally begin to occur at a later age than in men (on average with a delay of 10 years). Cessation of estrogen production also impacts metabolism, increasing the risk of developing obesity and diabetes. In middle-aged individuals, hypertension develops earlier and faster in women than in men, and smoking increases cardiovascular risk to a greater degree in women than it does in men. It is not only estrogen that affects female cardiovascular health and plays a protective role until menopause: other sex hormones such as progesterone and androgen hormones generate a complex balance that differentiates heart and blood vessel function in women compared to men. Estrogens improve vasodilation of epicardial coronary arteries and the coronary microvasculature by augmenting the release of vasodilating factors such as nitric oxide and prostacyclin, which are mechanisms of coronary vasodilatation that are more pronounced in women compared to men. Estrogens are also powerful inhibitors of inflammation, which in part explains their protective effects on CVD and chronic renal disease. Emerging evidence suggests that sex chromosomes also play a significant role in shaping cardiovascular risk. The cardiovascular protection conferred by endogenous estrogens may be extended by hormone therapy, especially using bioidentical hormones and starting treatment early after menopause.

The beneficial effects of tamoxifen on arteries: a key player for cardiovascular health of breast cancer patient

Breast cancer is the most common cancer in women. Over the past few decades, advances in cancer detection and treatment have significantly improved survival rate of breast cancer patients. However, due to the cardiovascular toxicity of cancer treatments (chemotherapy, anti-HER2 antibodies and radiotherapy), cardiovascular diseases (CVD) have become an increasingly important cause of long-term morbidity and mortality in breast cancer survivors. Endocrine therapies are prescribed to reduce the risk of recurrence and specific death in estrogen receptor-positive (ER+) early breast cancer patients, but their impact on CVD is a matter of debate. Whereas aromatase inhibitors and luteinizing hormone-releasing hormone (LHRH) analogs inhibit estrogen synthesis, tamoxifen acts as a selective estrogen receptor modulator (SERM), opposing estrogen action in the breast but mimicking their actions in other tissues, including arteries. This review aims to summarize the main clinical and experimental studies reporting the effects of tamoxifen on CVD. In addition, we will discuss how recent findings on the mechanisms of action of these therapies may contribute to a better understanding and anticipation of CVD risk in breast cancer patients.

Risk Factors and Outcomes During a First Acute Myocardial Infarction in Breast Cancer Survivors Compared with Females Without Breast Cancer

PURPOSE

The purpose of this research was to study the differences in epidemiology and outcomes of a first myocardial infarction in breast cancer survivors compared with the general female population in the United States.

METHODS

We retrospectively analyzed the US National Inpatient Sample years 2005-2015 to identify adult women with a first myocardial infarction. In this cohort, breast cancer survivors were identified. Outcomes evaluated were the differences in baseline demographics, comorbidities, and adjusted in-hospital mortality in women with and without breast cancer.

RESULTS

Among 1,644,032 first myocardial infarction cases in adult women, there were 56,842 (3.5%) breast cancer survivors. Compared with women without breast cancer, breast cancer survivors were 6 years older (mean age 77 vs 71 years, P < .001), had significantly higher prevalence of dyslipidemia and hypertension, and lower prevalence of obesity, diabetes mellitus, and smoking. Breast cancer survivors were more likely to have a non-ST segment elevation acute myocardial infarction and less likely to receive mechanical revascularization. In-hospital mortality was lower in breast cancer survivors (7.1%) compared with those without (7.9%, P < .001), findings that persisted after risk adjustment (odds ratio 0.89; 95% CI, 0.82-0.94).

CONCLUSIONS

Breast cancer survivors had a first acute myocardial infarction at an older age and had small but favorable differences in cardiovascular disease risk factors and outcomes compared with women without breast cancer. The favorable impact of health education, preventative medical care, greater motivation for a healthier lifestyle, and participation in cancer survivorship programs on these seemingly paradoxical findings in breast cancer survivors should be further explored.

Association between tamoxifen use and acute myocardial infarction in women with breast cancer

The relationship between tamoxifen use and acute myocardial infarction in women with breast cancer remains uncertain. The goal of the study was to assess whether tamoxifen use could be associated with acute myocardial infarction in women with breast cancer in Taiwan.A population-based case-control study was conducted to analyze the database of the Taiwan National Health Insurance Program. Totally, 489 women with breast cancer aged 20 to 84 years having the first episode of acute myocardial infarction from 2000 to 2011 were found as the cases. In addition, 1718 women with breast cancer aged 20 to 84 years without any type of ischemic heart disease were selected as the matched controls. Ever use of tamoxifen was classified as the studied women who had at least a prescription for tamoxifen before the index date. Never use of tamoxifen was classified as the studied women who never had a prescription for tamoxifen before the index date. We used the multivariable logistic regression model to estimate the odds ratio (OR) and 95% confidence interval (CI) for acute myocardial infarction associated with tamoxifen use.In a multivariable-adjusted analysis, women with acute myocardial infarction were 1.71 times more likely to be exposed to tamoxifen than those women without acute myocardial infarction (adjusted OR 1.71, 95% CI 1.38-2.13).The odds of tamoxifen use are 1.71 times higher in women with acute myocardial infarction versus those women without acute myocardial infarction in Taiwan.

Formestane as Treatment of Advanced Breast Cancer in Elderly Women

Aims and background

The number of elderly people is increasing, and the proportion of breast cancer in female cancer patients older than 65 years is 26%. In elderly patients, hormone therapy is widely accepted as the treatment of choice, because of its efficacy and good tolerability compared to chemotherapy. The aim of this study was to evaluate the endocrinologic and clinical activity of formestane (4-hydroxyandrostenedione), a selective aromatase inhibitor, in elderly patients with advanced breast cancer.

Methods

Thirty-five patients older than 65 years, selected from a larger group, were given formestane (250 mg or 500 mg i.m. fortnightly). Patients were evaluable for tumor response after 4 doses of formestane. Blood samples were collected to evaluate E2, FSH, LH, SHBG and DHEAS serum levels at baseline and after 2, 4, 8,12 and 24 weeks.

Results

Thirty patients had PS ≤ 1 (ECOG) and only 5 patients had PS = 2. Twenty-six patients were ER positive. Previous hormonal treatment for metastatic disease had been given to 17 patients; only 1 case had received chemotherapy. The overall response rate was 51% (95% C.I. 35–67%) and the median response duration was 9.5 months. Three complete responses were observed on viscera. The best responses were obtained on soft tissues (59%); on bone and viscera the response was respectively 45% and 47%. Local and systemic tolerability was highly satisfactory. Formestane induced prolonged suppression of E2 levels in all of the patients, and a significant reduction in SHBG levels was also observed from month 2 onward. A statistically significant ( P = 0.0001) rise in serum FSH was also observed during the therapy.

Conclusions

The study showed that formestane induced a long-lasting suppression of E2 levels and a satisfactory overall response. In our opinion, the drug is an effective and well-tolerated approach in the management of advanced breast cancer in elderly patients.

Changes in Serum Lipid and Lipoprotein Levels in Postmenopausal Patients with Node-Positive Breast Cancer Treated with Tamoxifen

Tamoxifen has been used for a long time as an adjuvant hormonal treatment in breast cancer patients. We studied 62 newly diagnosed postmenopausal women, aged 50-79 years, with node-positive breast cancer and receiving adjuvant tamoxifen (20 mg per day). Total serum cholesterol, triglycerides, HDL-cholesterol, LDL-cholesterol, VLDL-cholesterol, apo AI, apo AII, apo B and Lp(a) were determined before the surgery and 3, 6, 9, 12 and 24 months after starting tamoxifen treatment. Tamoxifen significantly reduced total serum cholesterol (6.13+/-1.20 mmol/L vs 5.21+/-1.05 mmol/L) (P <0.01), LDL-cholesterol (3.72+/-0.70 mmol/L vs 2.93+/-0.51) (P <0.01) and Lp(a) (0.11+/-0.07 g/L vs 0.02+/-0.01 g/L) (P < 0.01). There were no changes in triglycerides or HDL-cholesterol serum levels during tamoxifen treatment. The results indicate that an additional beneficial effect of adjuvant tamoxifen therapy may be that it decreases cardiovascular risk in such patients.

Update on cardiotoxicity of anti-cancer treatments

BACKGROUND AND AIMS

Anti-cancer treatments markedly improved the prognosis of patients, but unfortunately might be hampered by cardiotoxicity. Both symptomatic and asymptomatic clinical forms of heart failure have been reported, which may be reversible or irreversible. The aim of this review is to provide an overview of the antineoplastic agents associated with cardiac toxicity and of the available diagnostic techniques.

METHODS AND METHODS

This narrative review is based on material from MEDLINE and PUBMED up to November 2015. We looked at the terms antineoplastic drugs and cardiac toxicity in combination with echocardiography, troponins, cardiac magnetic resonance, and positron emission tomography.

RESULTS

Anthracyclines, monoclonal antibodies, fluoropyrimidines, taxanes, alkylating agents, vinka alkaloids were reported to induce different clinical manifestations of cardioxicity. Chest radiotherapy is also associated with various forms of cardiac damage, which are indistinguishable from those found in patients with heart disease of other aetiologies and that may even appear several years after administration. Among diagnostic techniques, echocardiography is a noninvasive, cost-effective, and widely available imaging tool. Nuclear imaging and cardiac magnetic resonance may be used but are not so widely available and are more difficult to perform. Finally, some biomarkers, such as troponins, may be used to evaluate cardiac damage, but establishing the optimal timing of troponin assessment remains unclear and defining the cut-off point for positivity is still an important goal.

CONCLUSIONS

Cardiotoxicity of anti-cancer treatments is associated with development of heart failure. Novel diagnostic tools might be relevant to early recognize irreversible forms cardiac diseases.

Nanotamoxifen Delivery System: Toxicity Assessment After Oral Administration and Biodistribution Study After Intravenous Delivery of Radiolabeled Nanotamoxifen

Tamoxifen is the most prescribed anticancer oral drug for increasing overall survival and decreasing recurrence and the risk of contralateral disease. However, some side effects, such as endometrial and liver tumors, thromboembolic disorders, and drug resistance, are associated with long-term tamoxifen treatment. We assessed the hematologic and organ toxicity after oral administration of three different doses of nanotamoxifen formulations. We also performed biodistribution studies of Technetium-99m ((99m)Tc)-nanotamoxifen after intravenous administration. The results demonstrated that nanotamoxifen was well-tolerated, with no adverse effect on biochemical parameters of blood and at the cellular level. Nitric oxide (NO) levels indicated no free radical formation. Oral nanotamoxifen is well-tolerated, with no hepatic or renal toxicity. Intravenous nanotamoxifen has potential to escape the liver, and is known for producing the harmful metabolite 4-hydroxytamoxifen (4OH-tamoxifen), which can cause uterine cancer.

Endoxifen, the active metabolite of tamoxifen, inhibits cloned hERG potassium channels

The effects of tamoxifen, and its active metabolite endoxifen (4-hydroxy-N-desmethyl-tamoxifen), on hERG currents stably expressed in HEK cells were investigated using the whole-cell patch-clamp technique and an immunoblot assay. Tamoxifen and endoxifen inhibited hERG tail currents at -50mV in a concentration-dependent manner with IC50 values of 1.2 and 1.6μM, respectively. The steady-state activation curve of the hERG currents was shifted to the hyperpolarizing direction in the presence of endoxifen. The voltage-dependent inhibition of hERG currents by endoxifen increased steeply in the voltage range of channel activation. The inhibition by endoxifen displayed a shallow voltage dependence (δ=0.18) in the full activation voltage range. A fast application of endoxifen induced a reversible block of hERG tail currents during repolarization in a concentration-dependent manner, which suggested an interaction with the open state of the channel. Endoxifen also decreased the hERG current elicited by a 5s depolarizing pulse to +60mV to inactivate the hERG currents, suggesting an interaction with the activated (open and/or inactivated) states of the channels. Tamoxifen and endoxifen inhibited the hERG channel protein trafficking to the plasma membrane in a concentration-dependent manner with endoxifen being more potent than tamoxifen. These results indicated that tamoxifen and endoxifen inhibited the hERG current by direct channel blockage and by the disruption of channel trafficking to the plasma membrane in a concentration-dependent manner. A therapeutic concentration of endoxifen inhibited the hERG current by preferentially interacting with the activated (open and/or inactivated) states of the channel.

Beneficial role of tamoxifen in isoproterenol-induced myocardial infarction

ER-α and ER-β agonist 17β-estradiol is reported to attenuate cardiac hypertrophy. Tamoxifen is a selective estrogen receptor modulator. Hence, the objective of this study was to investigate the effects of tamoxifen in myocardial infarction. For this, tamoxifen was administered to Sprague–Dawley rats for 1–14 days, and isoproterenol (ISO) (100 mg·(kg body mass)−1·day−1) was administered subcutaneously on the 13th and 14th days of the study in order to induce myocardial infarction, after which, various biochemical, cardiac, and morphometric parameters were evaluated. ISO produced significant dyslipidemia, hypertension, bradycardia, oxidative stress, and an increase in serum cardiac markers. Treatment with tamoxifen significantly controlled dyslipidemia, hypertension, bradycardia, oxidative stress, and reduced serum cardiac markers. The ISO control rats exhibited significant increases in the infarct size of the left ventricle (LV), LV cavity area, cardiac and LV hypertrophic indices, LV-wall thickness, cardiomyocyte diameter, and area. Treatment with tamoxifen significantly reduced infarction as well as hypertrophic and morphometric parameters. ISO also produced significant increases in the LV collagen level, decreases in Na+K+ATPase activity, and a reduction in the rate of pressure development and decay, which were prevented by tamoxifen treatment. The protective effect of tamoxifen on myocardial infarct was further confirmed by histopathological examination. Our data thus suggest that tamoxifen exerts beneficial effects in ISO-induced myocardial infarction.

Cardiotoxicity of systemic agents used in breast cancer

Several breast cancer therapies can lead to cardiovascular toxicity: drugs such anthracyclines can cause permanent damage, anti-HER2 agents may cause transitory and reversible cardiac dysfunction and others, such as those used in endocrine therapy, primarily disturb lipid metabolism. Considering the seriousness of these complications, trials are now being conducted to address cardiotoxicity associated with new drugs; however, to fully understand their toxicity profiles, longer follow-up is needed. In this review, we compile the information available about cardiac toxicity related to well-established systemic breast cancer treatments, as well as newer drugs, including antiangiogenics, mTOR inhibitors and novel anti-HER2 agents. We also describe current and next generation cardiac biomarkers and functional tests that can optimize treatment and reduce and prevent the incidence of treatment-related cardiotoxicity.

Association of tamoxifen use and reduced cardiovascular events among asian females with breast cancer

BACKGROUND

Tamoxifen is used for breast cancer treatment and has been reported to be beneficial for the cardiovascular system, but it is unclear whether tamoxifen exhibits a favorable cardiovascular effect in Asian patients.

METHODS AND RESULTS

From January, 1998 to December, 2006, a breast cancer cohort study was conducted using the Taiwan National Health Insurance database. Patients were divided according to whether tamoxifen was used. Study endpoints were occurrence of acute myocardial infarction (AMI), ischemic or hemorrhagic stroke and total cardiovascular events. A total of 3,690 female subjects were enrolled (mean age 50.1±11.3), 2,056 of whom received tamoxifen and 1,634 did not. During a mean follow-up of 6.9 years, the tamoxifen group had a significantly lower incidence of AMI (0.15% vs. 0.67%, P=0.008), ischemic stroke (1.99% vs. 3.30%, P=0.008), hemorrhagic stroke (0.15% vs. 0.55%, P=0.029), and total cardiovascular events (2.24% vs. 4.16%, P<0.001) than the non-exposed group. After adjusting for comorbidities, tamoxifen was independently associated with a reduced risk of myocardial infarction (hazard ratio [HR] 0.22; 95% confidence interval [CI] 0.07-0.70, ischemic stroke (HR 0.52; 95% CI 0.35-0.78), hemorrhagic stroke (HR 0.25; 95% CI 0.07-0.92), and total cardiovascular events (HR 0.54; 95% CI 0.37-0.78).

CONCLUSIONS

In Asian female breast cancer patients, tamoxifen use was associated with reduced risks of AMI, ischemic, hemorrhagic stroke and total cardiovascular events.

Long-term effects of continuing adjuvant tamoxifen to 10 years versus stopping at 5 years after diagnosis of oestrogen receptor-positive breast cancer: ATLAS, a randomised trial

BACKGROUND

For women with oestrogen receptor (ER)-positive early breast cancer, treatment with tamoxifen for 5 years substantially reduces the breast cancer mortality rate throughout the first 15 years after diagnosis. We aimed to assess the further effects of continuing tamoxifen to 10 years instead of stopping at 5 years.

METHODS

In the worldwide Adjuvant Tamoxifen: Longer Against Shorter (ATLAS) trial, 12,894 women with early breast cancer who had completed 5 years of treatment with tamoxifen were randomly allocated to continue tamoxifen to 10 years or stop at 5 years (open control). Allocation (1:1) was by central computer, using minimisation. After entry (between 1996 and 2005), yearly follow-up forms recorded any recurrence, second cancer, hospital admission, or death. We report effects on breast cancer outcomes among the 6846 women with ER-positive disease, and side-effects among all women (with positive, negative, or unknown ER status). Long-term follow-up still continues. This study is registered, number ISRCTN19652633.

FINDINGS

Among women with ER-positive disease, allocation to continue tamoxifen reduced the risk of breast cancer recurrence (617 recurrences in 3428 women allocated to continue vs 711 in 3418 controls, p=0·002), reduced breast cancer mortality (331 deaths vs 397 deaths, p=0·01), and reduced overall mortality (639 deaths vs 722 deaths, p=0·01). The reductions in adverse breast cancer outcomes appeared to be less extreme before than after year 10 (recurrence rate ratio [RR] 0·90 [95% CI 0·79–1·02] during years 5–9 and 0·75 [0·62–0·90] in later years; breast cancer mortality RR 0·97 [0·79–1·18] during years 5–9 and 0·71 [0·58–0·88] in later years). The cumulative risk of recurrence during years 5–14 was 21·4% for women allocated to continue versus 25·1% for controls; breast cancer mortality during years 5–14 was 12·2% for women allocated to continue versus 15·0% for controls (absolute mortality reduction 2·8%). Treatment allocation seemed to have no effect on breast cancer outcome among 1248 women with ER-negative disease, and an intermediate effect among 4800 women with unknown ER status. Among all 12,894 women, mortality without recurrence from causes other than breast cancer was little affected (691 deaths without recurrence in 6454 women allocated to continue versus 679 deaths in 6440 controls; RR 0·99 [0·89–1·10]; p=0·84). For the incidence (hospitalisation or death) rates of specific diseases, RRs were as follows: pulmonary embolus 1·87 (95% CI 1·13–3·07, p=0·01 [including 0·2% mortality in both treatment groups]), stroke 1·06 (0·83–1·36), ischaemic heart disease 0·76 (0·60–0·95, p=0·02), and endometrial cancer 1·74 (1·30–2·34, p=0·0002). The cumulative risk of endometrial cancer during years 5–14 was 3·1% (mortality 0·4%) for women allocated to continue versus 1·6% (mortality 0·2%) for controls (absolute mortality increase 0·2%).

INTERPRETATION

For women with ER-positive disease, continuing tamoxifen to 10 years rather than stopping at 5 years produces a further reduction in recurrence and mortality, particularly after year 10. These results, taken together with results from previous trials of 5 years of tamoxifen treatment versus none, suggest that 10 years of tamoxifen treatment can approximately halve breast cancer mortality during the second decade after diagnosis.

FUNDING

Cancer Research UK, UK Medical Research Council, AstraZeneca UK, US Army, EU-Biomed.

Increased aortic atherosclerotic plaque development in female apolipoprotein E-null mice is associated with elevated thromboxane A2 and decreased prostacyclin production

The production of thromboxane A(2) (TXA(2)) and prostacyclin (prostaglandin I(2), PGI(2)) is known to be increased in patients with atherosclerosis. In this study, we evaluated the influence of gender on TXA(2) and PGI(2) production, and their association with the progression of atherosclerosis in apolipoprotein E-null (ApoE(-/-)) mice maintained on a high fat diet for 3 months. En face analyses of aortas showed marked increases in plaque formation in female ApoE(-/-) mice. Quantification of the hematoxylin/eosin (H&E) stained cross sections of the aortic arch revealed 3 to 4-fold higher plaque thickness in female ApoE(-/-) mice. Analyses of 24-hours urine samples for 11-dehydro TXB(2) and 2, 3-dinor-6-keto PGF(1a) indicated that female ApoE(-/-) mice produce up to 15-fold more TXA(2) and 50% less PGI(2) than the age matched males. Interestingly, the serum cholesterol levels in ApoE(-/-) females were 20% lower than males on the high fat regimen. No gender-associated changes in the number of T lymphocytes, mast cells and macrophages were evident in the lesion areas of ApoE(-/-) mice. The results suggest that the markedly elevated TXA(2) production and reduced PGI(2) production are gender-related proatherogenic risk factors in female ApoE(-/-) mice.

Potential role of UGT pharmacogenetics in cancer treatment and prevention: focus on tamoxifen and aromatase inhibitors

Tamoxifen (TAM) is a selective estrogen-receptor modulator that is widely used in the prevention and treatment of estrogen-receptor-positive breast cancer. Its use has significantly contributed to a decline in breast cancer mortality, since breast cancer patients treated with TAM for 5 years exhibit a 30-50% reduction in both the rate of disease recurrence after 10 years of patient follow-up and in the occurrence of contralateral breast cancer. However, in patients treated with TAM, there is substantial interindividual variability in the development of resistance to TAM therapy and in the incidence of TAM-induced adverse events, including deep-vein thrombosis, hot flashes, and the development of endometrial cancer. Aromatase inhibitors (AIs) have emerged as a viable alternative to TAM, working by inhibiting aromatase activity and blocking estrone/estrodiol biosynthesis in postmenopausal women. The current third-generation AIs, anastrozole, exemestane, and letrozole, were used initially for the treatment of metastatic breast cancer, demonstrating similar or greater benefit but less toxicity, compared with TAM, and are now being employed as adjuvant treatment for early breast cancer in postmenopausal women. This article will focus on the UDP-glucuronosyltransferases, a family of metabolizing enzymes that play an important role in the deactivation and clearance of TAM, anastrazole, and exemestane, and how interindividual differences in these enzymes may play a role in patient response to these agents.

Tamoxifen inhibits inward rectifier K+ 2.x family of inward rectifier channels by interfering with phosphatidylinositol 4,5-bisphosphate-channel interactions

Tamoxifen, an estrogen receptor antagonist used in the treatment of breast cancer, inhibits the inward rectifier potassium current (I(K1)) in cardiac myocytes by an unknown mechanism. We characterized the inhibitory effects of tamoxifen on Kir2.1, Kir2.2, and Kir2.3 potassium channels that underlie cardiac I(K1). We also studied the effects of 4-hydroxytamoxifen and raloxifene. All three drugs inhibited inward rectifier K(+) 2.x (Kir2.x) family members. The order of inhibition for all three drugs was Kir2.3 > Kir2.1 approximately Kir2.2. The onset of inhibition of Kir2.x current by these compounds was slow (T(1/2) approximately 6 min) and only partially recovered after washout ( approximately 30%). Kir2.x inhibition was concentration-dependent but voltage-independent. The time course and degree of inhibition was independent of external or internal drug application. We tested the hypothesis that tamoxifen interferes with the interaction between the channel and the membrane-delimited channel activator, phosphatidylinositol 4,5-bisphosphate (PIP(2)). Inhibition of Kir2.3 currents was significantly reduced by a single point mutation of I213L, which enhances Kir2.3 interaction with membrane PIP(2). Pretreatment with PIP(2) significantly decreased the inhibition induced by tamoxifen, 4-hydroxytamoxifen, and raloxifene on Kir2.3 channels. Pretreatment with spermine (100 microM) decreased the inhibitory effect of tamoxifen on Kir2.1, probably by strengthening the channel's interaction with PIP(2). In cat atrial and ventricular myocytes, 3 microM tamoxifen inhibited I(K1), but the effect was greater in the former than the latter. The data strongly suggest that tamoxifen, its metabolite, and the estrogen receptor inhibitor raloxifene inhibit Kir2.x channels indirectly by interfering with the interaction between the channel and PIP(2).

Comparative analysis of oestrogen and raloxifene effects on the phospholipid composition of high density lipoproteins in healthy postmenopausal women

The beneficial effect of selective oestrogen receptor modulators such as raloxifene in cardiovascular disease may be mediated partly by favourable changes in the phospholipid composition of high density lipoprotein (HDL) subclasses. In Group A (oestrogen alone) HDL2 phosphatidylcholine increased (P<0.001), while there was a decrease in HDL2 phosphatidylinositol (P<0.05) and HDL2 phosphatidylethanolamine (P<0.05) compared to controls (baseline). In the same group, HDL3 phosphatidylcholine increased (P<0.001) and HDL3 phosphatidylethanolamine decreased (P<0.01). In Group B (raloxifene) HDL2 phosphatidylcholine increased (P<0.001) as well as HDL2 diphosphatidylglycerol (P<0.01) while there were decreases in HDL2 sphingomyelin (P<0.01) and HDL2 phosphatidylethanolamine (P<0.05). In the same group, an increase in HDL3 phosphatidylcholine (P<0.001) and a reduction in HDL3 phosphatidylinositol (P<0.05) were observed as well as a decrease in HDL3 phosphatidylethanolamine (P<0.01) and HDL3 diphosphatidylglycerol (P<0.05). The significance of these results is discussed.

Potential role of UGT pharmacogenetics in cancer treatment and prevention: focus on tamoxifen

Tamoxifen (TAM) is a selective estrogen receptor modulator that is widely used in the prevention and treatment of estrogen receptor-positive (ER(+)) breast cancer. Its use has significantly contributed to a decline in breast cancer mortality, since breast cancer patients treated with TAM for 5 years exhibit a 30-50% reduction in both the rate of disease recurrence after 10 years of patient follow-up and occurrence of contralateral breast cancer. However, in patients treated with TAM there is substantial interindividual variability in the development of resistance to TAM therapy, and in the incidence of TAM-induced adverse events, including deep vein thrombosis, hot flashes, and the development of endometrial cancer. This article will focus on the UDP glucuronosyltransferases, a family of metabolizing enzymes that are responsible for the deactivation and clearance of TAM and TAM metabolites, and how interindividual differences in these enzymes may play a role in patient response to TAM.

GnRH analogues in the treatment of fibroids

Uterine fibroids are estimated to affect up to 25% of women of reproductive age and are a common cause of morbidity, being associated with menstrual dysfunction, iron deficiency anaemia, pregnancy wastage and subfertility. Their pathogenesis remains unknown but their association with ovarian function and oestrogen production is undisputed and supported by their occurrence only after puberty and the shrinkage observed after the menopause. This oestrogen dependency has recently been exploited therapeutically through investigation of the use of agents that induce a hypo-oestrogenic state, the gonadotrophin-releasing hormone (GnRH) or luteinizing hormone-releasing hormone (LHRH) analogues.

Functional significance of UDP-glucuronosyltransferase variants in the metabolism of active tamoxifen metabolites

Tamoxifen (TAM) is a selective estrogen receptor modulator widely used in the prevention and treatment of breast cancer. A major mode of metabolism of the major active metabolites of TAM, 4-OH-TAM and endoxifen, is by glucuronidation via the UDP-glucuronosyltransferase (UGT) family of enzymes. To examine whether polymorphisms in the UGT enzymes responsible for the glucuronidation of active TAM metabolites play an important role in interindividual differences in TAM metabolism, cell lines overexpressing wild-type or variant UGTs were examined for their activities against TAM metabolites in vitro. For variants of active extrahepatic UGTs, the UGT1A8(173Ala/277Tyr) variant exhibited no detectable glucuronidation activity against the trans isomers of either 4-OH-TAM or endoxifen. Little or no difference in TAM glucuronidating activity was observed for the UGT1A8(173Gly/277Cys) or UGT1A10(139Lys) variants compared with their wild-type counterparts. For active hepatic UGTs, the UGT2B7(268Tyr) variant exhibited significant (P < 0.01) 2- and 5-fold decreases in activity against the trans isomers of 4-OH-TAM and endoxifen, respectively, compared with wild-type UGT2B7(268His). In studies of 111 human liver microsomal specimens, the rate of O-glucuronidation against trans-4-OH-TAM and trans-endoxifen was 28% (P < 0.001) and 27% (P = 0.002) lower, respectively, in individuals homozygous for the UGT2B7 Tyr(268)Tyr genotype compared with subjects with the UGT2B7 His(268)His genotype, with a significant (P < 0.01) trend of decreasing activity against both substrates with increasing numbers of the UGT2B7(268His) allele. These results suggest that functional polymorphisms in TAM-metabolizing UGTs, including UGT2B7 and potentially UGT1A8, may be important in interindividual variability in TAM metabolism and response to TAM therapy.

Tamoxifen treatment in Danish breast cancer patients and 5-year risk of arterial atherosclerotic events: a null association

Although the effectiveness of tamoxifen in preventing the recurrence of breast cancer is well established, associations between tamoxifen and the occurrence of atherosclerotic events are not as clear. Breast cancer patients taking tamoxifen have lower serum cholesterol and other lipid levels than those not taking tamoxifen, suggesting that tamoxifen might prevent atherosclerotic events, but the existing studies are conflicting. We examined the relation between tamoxifen and incident hospitalization of angina pectoris, acute myocardial infarction, heart failure, and stroke. The study population of 16,289 women was identified from the Danish Breast Cancer Cooperative Group nationwide clinical database and includes women diagnosed with stage I or II estrogen receptor-positive breast cancer between 1990 and 2004 at ages 45 to 69. Use of a large population-based sample with complete outcome ascertainment allowed us to calculate precise measures of risks, risk ratios, and adjusted hazard ratios comparing tamoxifen-treated patients with untreated patients. We found strong evidence for null associations for each of the four outcomes of interest during the first year and first 5 years after the start of therapy. These findings are important in risk/benefit analyses as tamoxifen therapy in postmenopausal women is being replaced with aromatase inhibitors.

A case of coronary embolism in a patient with paroxysmal atrial fibrillation receiving tamoxifen

Coronary embolism is an uncommon cause of myocardial infarction which should be considered especially in patients with associated conditions like atrial fibrillation, intracardiac prosthesis or infective endocarditis. We present the case of a 64-year-old man with lone paroxysmal AF who sustained an acute anterior wall infarction due to an embolism in the LAD. The patient was being treated with tamoxifen for benign gynaecomastia. The case illustrates some therapeutic problems of embolic myocardial infarction. Rescue PTCA after unsuccessful thrombolysis first resulted in distal embolization in diagonal branches with the need for aggressive anticoagulation. While the final angiographic result was satisfactory, the patient died of an intracranial hemorrhage. We present a short overview of the therapeutic options of coronary embolism and discuss the effect of the selective estrogen receptor modulator tamoxifen on arterial and venous thromboembolic disease which is suggestive of a pathogenic role.

Glucuronidation of active tamoxifen metabolites by the human UDP glucuronosyltransferases

Tamoxifen (TAM) is an antiestrogen that has been widely used in the treatment and prevention of breast cancer in women. One of the major mechanisms of metabolism and elimination of TAM and its major active metabolites 4-hydroxytamoxifen (4-OH-TAM) and 4-OH-N-desmethyl-TAM (endoxifen; 4-hydroxy-N-desmethyl-tamoxifen) is via glucuronidation. Although limited studies have been performed characterizing the glucuronidation of 4-OH-TAM, no studies have been performed on endoxifen. In the present study, characterization of the glucuronidating activities of human UDP glucuronosyltransferases (UGTs) against isomers of 4-OH-TAM and endoxifen was performed. Using homogenates of individual UGT-overexpressing cell lines, UGTs 2B7 approximately 1A8 > UGT1A10 exhibited the highest overall O-glucuronidating activity against trans-4-OH-TAM as determined by Vmax/K(M), with the hepatic enzyme UGT2B7 exhibiting the highest binding affinity and lowest K(M) (3.7 microM). As determined by Vmax/K(M), UGT1A10 exhibited the highest overall O-glucuronidating activity against cis-4-OH-TAM, 10-fold higher than the next-most active UGTs 1A1 and 2B7, but with UGT1A7 exhibiting the lowest K(M). Although both N- and O-glucuronidation occurred for 4-OH-TAM in human liver microsomes, only O-glucuronidating activity was observed for endoxifen; no endoxifen-N-glucuronidation was observed for any UGT tested. UGTs 1A10 approximately 1A8 > UGT2B7 exhibited the highest overall glucuronidating activities as determined by Vmax/K(M) for trans-endoxifen, with the extrahepatic enzyme UGT1A10 exhibiting the highest binding affinity and lowest K(M) (39.9 microM). Similar to that observed for cis-4-OH-TAM, UGT1A10 also exhibited the highest activity for cis-endoxifen. These data suggest that several UGTs, including UGTs 1A10, 2B7, and 1A8 play an important role in the metabolism of 4-OH-TAM and endoxifen.

Elimination of antiestrogenic effects of active tamoxifen metabolites by glucuronidation

1-[4-(2-Dimethylaminoethoxy)-phenyl]-1,2-diphenylbut-1-(Z)-ene (tamoxifen, TAM) is a nonsteroidal antiestrogen that has been commonly used for the prevention and treatment of estrogen receptor-positive breast cancer. TAM is extensively metabolized into several primary active metabolites including 4-hydroxy-TAM (4-OH-TAM) and endoxifen. Glucuronidation is the major phase II metabolic pathway important in their excretion. Whereas high antiestrogenic activity has been reported for both 4-OH-TAM and endoxifen, studies examining the effect of glucuronide conjugation of these metabolites have not previously been performed. In the present study, the antiestrogenic activities of glucuronidated TAM metabolites were determined by examining their effect on the induction of the estrogen-responsive progesterone receptor (PGR) gene. 17beta-Estradiol (E(2))-mediated PGR gene expression in MCF-7 cells was determined by real-time reverse transcriptase-polymerase chain reaction for each TAM metabolite isomer. E(2) (1 x 10(-10) M) induction of PGR mRNA was 6-fold after a 12-h incubation; only unconjugated TAM metabolites inhibited this effect. A virtually identical dose-dependent inhibition of E(2)-induced PGR gene expression was found for both the trans- and cis-isomers of 4-OH-TAM and endoxifen, with maximal inhibition attained at 1 x 10(-6) M of TAM metabolite. The glucuronide conjugates of all 4-OH-TAM and endoxifen isomers exhibited no effect on E(2)-mediated induction of PGR expression at all concentrations of TAM metabolite examined in this study. These data indicate that isomers of both 4-OH-TAM and endoxifen exhibit roughly equipotent antiestrogenic effects on E(2)-induced gene expression and that glucuronide conjugates of the same metabolites effectively negate this activity. This result may have important implications in terms of both whole-body and target tissue-specific glucuronidation pathways and individual responses to TAM therapy and cancer prevention.

SERMs: Meeting the Promise of Multifunctional Medicines

The successful development and clinical evaluation of the selective estrogen receptor modulators in the Study of Tamoxifen and Raloxifene trial provides an occasion to reflect on the milestone that has been achieved and the potential for further progress in the chemoprevention of breast cancer. The evolution of tamoxifen from a successful treatment for breast cancer to the first chemopreventive for any cancer took two decades. Clinicians gained an enormous amount of experience with the use of tamoxifen as a treatment, and, as a result, there were few surprises in terms of efficacy or the side effect profile when the medicine was used to prevent breast cancer in high-risk women. In contrast, raloxifene emerged via the novel path of the evidence-based hypothesis that a drug targeted at one disease, osteoporosis, could also prevent breast cancer. Changes in health care strategies to implement chemoprevention take time, but the evidence now suggests that chemoprevention has become a reality in clinical practice.

Tamoxifen treatment of myocardial infarcted female rats exacerbates scar formation

Hormonal replacement therapy in postmenopausal women was associated with an increased incidence of nonfatal myocardial infarction. Selective estrogen receptor modulators were considered an alternative pharmacological approach. However, selective estrogen receptor modulators acting via estrogen receptor-dependent and receptor-independent mechanisms may negatively influence cardiac remodeling. The present study tested the hypothesis that tamoxifen (TAM) treatment after coronary artery ligation compromised scar formation. TAM administration (10 mg kg(-1) day(-1) for 3 weeks) to postmyocardial infarcted (MI) female adult rats significantly increased scar surface area (TAM+MI = 0.67 +/- 0.08 vs MI = 0.45 +/- 0.06 cm(2)) and weight (TAM+MI = 0.071 +/- 0.007 vs MI = 0.050 +/- 0.006 grams). In the infarct region, a significant decrease (p < 0.05) of small calibre vessels (lumen diameter <50 microm) was observed in TAM treated post-MI rats (4.5 +/- 0.8 vessels/mm(2)), as compared to untreated MI rats (7 +/- 0.7 vessels/mm(2)). Consistent with the latter finding, 4-OH TAM caused a dose-dependent suppression of vascular endothelial growth factor (VEGF)-stimulated (10(-9) mol/l) capillarity-like tubule formation by rat aortic endothelial cells in vitro via an estrogen receptor-independent mechanism. These data have demonstrated that TAM treatment of post-MI female rats exacerbated scar formation and may have occurred at least in part via the attenuation of new vessel formation in the infarct region.

Characterization of tamoxifen and 4-hydroxytamoxifen glucuronidation by human UGT1A4 variants

Introduction

Tamoxifen (TAM) is an antiestrogen widely used in the treatment and prevention of breast cancer in women. One of the major mechanisms of metabolism of TAM and one of its major active metabolites, 4-hydroxytamoxifen (4-OH-TAM), is via glucuronidation. In the present study, the glucuronidating activities of three common variant isoforms encoded by the human UDP-glucuronosyltransferase (UGT) 1A4 gene were examined against TAM, trans-4-OH-TAM and cis-4-OH-TAM.

Methods

HPLC was used to detect glucuronide conjugates in microsomes from UGT1A4-overexpressing HK293 cells. The UGT1A4 wild-type cDNA was synthesized by RT-PCR using normal human liver total RNA. The UGT1A4^24Thr/48Leu and UGT1A4^24Pro/48Val variants were generated by site-directed mutagenesis of the pcDNA3.1/V5-His-TOPO plasmid expressing wild-type UGT1A4^24Pro/48Leu. Levels of UGT1A4 expression in UGT-overexpressing cell lines were measured by western blot analysis.

Results

Microsomes from wild-type UGT1A4^24Pro/48Leu-overexpressing HK293 cells exhibited significant levels of activity against TAM, trans-4-OH-TAM and cis-4-OH-TAM, forming exclusively the tamoxifen quaternary ammonium glucuronide (TAM-N⁺-glucuronide) and the 4-hydroxytamoxifen quaternary ammonium glucuronides (trans-4-OH-TAM-N⁺-glucuronide and cis-4-OH-TAM-N⁺-glucuronide) with apparent K_m values of 2.0 μM, 2.2 μM, and 2.1 μM, respectively. Higher glucuronidation activities were found by kinetic analysis for microsomes from the variant UGT1A4^24Pro/48Val-overexpressing cell line as compared with microsomes from wild-type UGT1A4^24Pro/48Leu-overexpressing cells against TAM and against both the trans and cis isomers of 4-OH-TAM. A significantly (P < 0.02) lower K_m value (~1.6-fold to 1.8-fold) was observed for both 4-OH-TAM isomers, while a near-significant (P = 0.053) decrease in K_m was observed for TAM for the UGT1A4^24Pro/48Val variant as compared with wild-type UGT1A4. The V_max/K_m ratio for the UGT1A4^24Pro/48Val variant was significantly (P ≤ 0.005) higher than that observed for the wild-type UGT1A4 isoform for both the trans and cis isomers of 4-OH-TAM after normalization for UGT1A4 expression by western blotting. No significant effect on enzyme kinetics was observed for the UGT1A4^24Thr/48Leu variant against either isomer of 4-OH-TAM or with TAM.

Conclusion

These data suggest that the UGT1A4 codon 48 Leu>Val polymorphism significantly alters glucuronidation rates against TAM and its active hydroxylated metabolites, and that this polymorphism may play an important role in individual pharmacological response to TAM therapy.

Aromatase inhibitors and cardiac toxicity: getting to the heart of the matter

Recent advances in breast cancer treatment include the advent of aromatase inhibitors (AIs) in the adjuvant setting with better efficacy and toxicity profiles than tamoxifen. However, AIs generally do not improve lipid profile as tamoxifen does, and there has been suggestion of increased cardiovascular risk with AI use. This has become an area of concern, particularly in light of the view that tamoxifen may protect against cardiovascular disease. This review of the current literature and updated trial data examines the effect both AIs and tamoxifen have on lipids and cardiovascular risk. It also highlights the importance of interpreting such data within the larger context of cardiovascular health in postmenopausal women.

Management of early breast cancer in the elderly

Breast cancer is the most common malignancy in women with an age related increase in incidence ranging from 1 in 50 at age 50 to 1 in 10 at age 80. This is particularly significant in view of the changing demographics in the western population, characterised by an aging population and increased life expectancy. However in spite of favourable prognostic factors and less aggressive biological behaviour, elderly breast cancer patients receive less aggressive treatment when compared with their younger counterparts. Appropriate treatment should be offered depending on physiological reserve and comorbidities. Primary endocrine treatment has been shown to be associated with significant morbidity in terms of disease progression. Prompt surgery and adjuvant treatment can decrease relapse and improve survival. Radiation therapy is shown to decrease local relapse and chemotherapy may have a role in a select group of patients with adverse prognostic factors. With incidence of breast cancer bound to increase in the elderly population, it is essential to establish optimum therapy in this cohort of patients as studies reveal good outcome from standard treatment.

Tamoxifen and estrogen attenuate enhanced vascular reactivity induced by estrogen deficiency in rat carotid arteries

Recent clinical trials showed that estrogen usage in postmenopausal women did not affect coronary heart disease incidence, in contrast to several laboratory studies showing that estrogen decreased vascular reactivity. We speculated that, in some arteries, estrogen deficiency enhances endothelial function to compensate for the increased vascular smooth muscle reactivity. In this study, we examined the role of endothelium-derived vasoactive factors and the influence of in vivo estrogen and/or tamoxifen treatment on vascular reactivity of estrogen-deficient rats. Common carotid arteries were isolated from sham-operated (control), ovariectomized (Ovx), estrogen- or tamoxifen-treated Ovx rats, and Ovx rats co-treated with estrogen and tamoxifen. U46619 or phenylephrine induced similar contractions in endothelium-intact rings from all groups. Interestingly, removal of endothelium unmasked enhanced contractions in Ovx rats, which was prevented by estrogen, tamoxifen, or estrogen+tamoxifen treatment. Contractions to high K(+) were higher in both endothelium-intact and endothelium-denuded arteries from Ovx rats. Estrogen or tamoxifen treatment normalized high K(+)-induced contraction. A gap junction blocker, 18alpha-glycyrrhetinic acid, revealed enhanced contractions to U46619 in the absence or presence of l-NNA. Western blotting showed enhanced expressions of gap junctional connexin 43 in Ovx group. This study suggests that ovariectomy increases functional expression of gap junction-mediated endothelium-derived hyperpolarizing factor. Also, vascular effects of ovariectomy can be reversed by estrogen, tamoxifen or estrogen+tamoxifen treatment, suggesting that tamoxifen confers estrogenic effects in the vascular system.

Cost-effectiveness of exemestane versus tamoxifen as adjuvant therapy for early-stage breast cancer after 2-3 years treatment with tamoxifen in Sweden

Aromatase inhibitors are rapidly becoming the cornerstone of endocrine treatment for advanced disease and are now also used as adjuvant treatment in early-stage disease. The objective of this study was to assess the cost-effectiveness of adjuvant treatment with exemestane versus tamoxifen for early-stage breast cancer after 2-3 years treatment with tamoxifen in Sweden. The results are based on findings in the Intergroup Exemestane Study (IES). IES was a randomized controlled trial in which postmenopausal women who had received 2-3 years of tamoxifen therapy following primary treatment of early-stage breast cancer, were randomized to either continue on tamoxifen therapy or be switched to exemestane therapy. The results showed a disease-free survival hazard ratio of exemestane relative to tamoxifen in IES of 0.69. A Markov state-transition model was developed to simulate consequences after the end of the clinical trial, and to integrate the trial data with external data on mortality, costs and quality of life specific for Swedish women. The cost per QALY gained was about euro 20,000 in the base case analysis without inclusion of consequences of coronary heart disease. Inclusion of these events increased the cost-effectiveness ratio to about euro 31,000. This means that, based on our assumption, sequential exemestane treatment in early breast cancer is a cost-effective option compared with tamoxifen alone, although more long-term data on overall survival and consequences of adverse events would be valuable to increase the validity of the analysis further.

Tamoxifen dilates porcine coronary arteries: roles for nitric oxide and ouabain-sensitive mechanisms

BACKGROUND AND PURPOSE

Experiments were designed to determine the mechanism of the relaxation induced by tamoxifen in porcine coronary arteries at the tissue, cellular and molecular levels.

EXPERIMENTAL APPROACH

Porcine left circumflex coronary arteries were isolated and isometric tension was measured. [Ca2+]i in native endothelial cells of intact arteries was determined by a calcium fluorescence imaging technique and eNOS ser1177 phosphorylation was assayed by Western blotting.

KEY RESULTS

Tamoxifen induced an endothelium-dependent relaxation that was antagonized by ICI 182,780 and abolished by NG-nitro-L-arginine methyl ester (L-NAME) or 1H-[1,2,4]oxadizolo[4,3-a]quinoxalin-1-one (ODQ). L-Arginine reversed the effect of L-NAME while indomethacin was without effect. Tamoxifen-induced relaxation was attenuated by charybdotoxin (CTX) plus apamin, ouabain or by incubation in a K+ -free solution. Moreover, tamoxifen triggered extracellular Ca2+ -dependent increases in endothelial [Ca2+]i and this effect was abolished by ICI 182,780. Endothelium-independent relaxation to sodium nitroprusside was also inhibited by ouabain or in a K+ -free solution. Furthermore, tamoxifen increased endothelial nitric oxide synthase (eNOS) phosphorylation at Ser-1177 and ICI 182,780 prevented this effect.

CONCLUSIONS AND IMPLICATIONS

The present results suggest that tamoxifen mainly induces endothelium-dependent relaxation and that endothelial nitric oxide (NO) is the primary mediator of this effect. NO-dependent responses may result from elevated [Ca2+]i in endothelial cells; an effect abolished by ICI 182,780. NO activates Na+/K+ -ATPase in vascular smooth muscle, leading to relaxation. These results suggest that tamoxifen is able to modulate eNOS phosphorylation directly.

Comprehensive side-effect profile of anastrozole and tamoxifen as adjuvant treatment for early-stage breast cancer: long-term safety analysis of the ATAC trial

BACKGROUND

The Arimidex (anastrozole), Tamoxifen, Alone or in Combination (ATAC) trial was designed to compare the efficacy and safety of anastrozole with tamoxifen as adjuvant treatment for postmenopausal women with early-stage breast cancer. After an extended follow-up beyond the 5 years of treatment, we aimed to assess the safety, tolerability, and risk-benefit indices of these compounds.

METHODS

We analysed postmenopausal women (mean age 64 years [SD 9]) with localised breast cancer randomly assigned to anastrozole (n=3125) or tamoxifen (n=3116). Efficacy measures, including death and risk-benefit indices, were analysed by intention to treat. Safety analyses were based on treatment first received (n=3092 for anastrozole and n=3094 tamoxifen). We calculated a risk-benefit analysis using the two global indices for the Women's Health Initiative and for Disease-Free Survival and Serious Adverse Events. This study is registered as an International Standard Randomised Controlled Trial, number ISRCTN18233230.

FINDINGS

At median follow-up of 68 months (range 1-93), treatment-related adverse events occurred significantly less often with anastrozole than with tamoxifen (1884 [61%] vs 2117 [68%]; p<0.0001), as did treatment-related serious adverse events (146 [5%] vs 277 [9%]; p<0.0001) and adverse events leading to withdrawal (344 [11%] vs 442 [14%]; p=0.0002). Patients given anastrozole had significantly fewer overall events for the Global Index of the Women's Health Initiative (744 [24%] vs 851 [27%]; hazard ratio 0.85 [95% CI 0.77-0.94], p=0.001) and the Global Index of Disease-Free Survival and Serious Adverse Events (1453 [46%] vs 1594 [51%]; 0.88 [0.82-0.94]; p=0.0004).

INTERPRETATION

Anastrozole is tolerated better than tamoxifen by postmenopausal women with early-stage breast cancer, and results in fewer serious adverse events. Furthermore, it has a more favourable overall risk-benefit profile and lower recurrence rate than tamoxifen.

Adjuvant Hormonal Therapy in Peri‐ and Postmenopausal Breast Cancer

Tamoxifen has been the mainstay of endocrine treatment for early-stage breast cancer in both premenopausal and postmenopausal women for many years. Since 2001, the results of several large, randomized, clinical trials have provided evidence that aromatase inhibitor (AI) therapy, either upfront or in sequence after tamoxifen, improves disease-free survival and, in certain patients, overall survival for postmenopausal patients with hormone receptor-positive breast cancer. Thus far, with relatively short-term follow-up, AIs have been generally safe and well tolerated among the population of patients treated in these adjuvant trials. However, important side effects such as musculoskeletal and bone-related problems, including the risk for osteoporosis and fractures, remain of concern and warrant continued monitoring and follow-up. Several questions regarding the appropriate AI to use and the timing of AI therapy remain unresolved, and ongoing studies will help address these issues. Caution is warranted in the use of AIs in perimenopausal women, including those that develop chemotherapy-induced amenorrhea, and clinical evidence supports the role for AI use in postmenopausal women only. Areas of active investigation include the mechanisms of resistance to endocrine therapy with tamoxifen and AIs and clinical strategies to overcome this resistance.

Anastrozole as an adjuvant endocrine treatment for postmenopausal patients with breast cancer: emerging data

The Arimidex, Tamoxifen, Alone or in Combination (ATAC) trial compared the efficacy and safety of anastrozole versus tamoxifen versus the combination as initial adjuvant treatment for early breast cancer in over 9,000 postmenopausal women. Analyses at 33 and 47 months median follow-up showed that anastrozole significantly prolonged disease-free survival and time to recurrence and reduced the incidence of contralateral breast cancer compared with tamoxifen. Results of the completed treatment analysis at 68 months median follow-up confirmed the earlier findings, showing that the absolute difference in disease-free survival continued to increase beyond completion of treatment. Mature safety data from the ATAC trial show that, overall, anastrozole has a favorable safety profile compared with tamoxifen. In the absence of current data on further follow-up or the outcome of trials investigating proactive sequencing of endocrine therapies, we present a model based on several trials, including ATAC. This model suggests that using an aromatase inhibitor as initial adjuvant therapy is a better option than switching to an aromatase inhibitor after >/=2 years of tamoxifen. The relative toxicities of the three approved third-generation aromatase inhibitors, anastrozole, letrozole, and exemestane, are discussed. These data suggest that long-term safety profiles may differ between aromatase inhibitors, although comprehensive comparative data for letrozole and exemestane versus tamoxifen are lacking.

Letrozole as adjuvant endocrine therapy in postmenopausal women with breast cancer

The third-generation aromatase inhibitor letrozole offers a promising approach to treating hormone-sensitive breast cancer for postmenopausal women, through potent and specific inhibition of estrogen synthesis. In neoadjuvant and first-line treatment, letrozole demonstrated superior efficacy compared with tamoxifen in randomized Phase III trials. Initial results of Breast InterGroup 1-98, a large ongoing randomized trial investigating primary adjuvant endocrine treatment with either letrozole or tamoxifen, have recently been presented. Patients treated with letrozole demonstrated a 19% improvement in disease-free survival and a significant reduced risk of distant recurrences, holding out the prospect of a survival advantage over tamoxifen treatment with further maturation of the trial. For patients who have already completed 5 years of tamoxifen, extended endocrine therapy with letrozole is a new therapeutic option based on the results of the MA-17 trial. The optimal use of aromatase inhibitors remains an open question, at least until results from randomized trials (BIG 1-98, TEAM) investigating the sequential use of an aromatase inhibitor and tamoxifen in comparison with continuous monotherapy become available.

Emerging Selective Estrogen Receptor Modulators

Menopause, regardless of age at onset, is associated with a marked increase in coronary heart disease (CHD) risk. On the basis of epidemiological studies that demonstrated mainly positive effects of postmenopausal hormone therapy on CHD as well as on risk markers of CHD, it has been suggested that CHD could be prevented in postmenopausal women with long-term hormone therapy. However, since the publications of the Heart and Estrogen/progestin Replacement Study and the Women's Health Initiative trial, prescription of hormone therapy for the prevention of CHD has become controversial. Major efforts have been made to identify alternatives for hormone therapy. Compounds suggested have included selective estrogen receptor modulators (SERMs), which represent a class with a growing number of compounds that act as either estrogen receptor agonists or antagonists in a tissue-specific manner. This pharmacological profile may offer the opportunity to dissociate favourable estrogenic effects on the bone and cardiovascular system from unfavourable stimulatory effects on the breast and endometrium. Two SERMs presently on the market are tamoxifen and raloxifene. The only data available regarding the effects of tamoxifen on cardiovascular events in postmenopausal women are from breast cancer trials. These trials found fewer fatal myocardial events in women randomly assigned to tamoxifen compared with women assigned to placebo. Raloxifene is a second-generation SERM that has been shown to prevent osteoporotic fractures, is safe for the endometrium and holds high promise for the prevention of breast cancer. The effect of raloxifene on CHD is still uncertain. On the basis of the MORE (Multiple Outcomes of Raloxifene Evaluation) trial, raloxifene may offer some protection to women with CHD or to those who are at high risk of CHD. Proof that raloxifene reduces the risk of CHD requires a clinical trial with hard clinical endpoints. Such a study is currently underway. Next-generation SERMs taken into clinical development include idoxifene, droloxifene, ospemifene, arzoxifene, acolbifene/EM-800, levormeloxifene, lasofoxifene, bazedoxifene and HMR 3339. The aim is to find a compound with the ideal profile, that is, alleviation of climacteric symptoms and prevention of osteoporotic fractures, but without an adverse effect on the breast and endometrium, and no negative effect or even a beneficial effect on the cardiovascular system and the brain. Currently, limited data are available with regard to these next-generation SERMs and CHD. Nevertheless, some of these novel agents provide arguments for continuing the search for an ideal SERM.

Coronary Heart Disease Mortality After 5 Years of Adjuvant Tamoxifen Therapy: Results from a Randomized Trial

From January 1, 1983, through December 31, 1992, a total of 4610 patients entered a randomized trial that compared mortality among patients receiving 2 years of adjuvant tamoxifen therapy with that in patients receiving 5 years of adjuvant tamoxifen therapy, 4175 of whom were recurrence free after 2 years of tamoxifen therapy. Among the 2046 patients randomly assigned to the 5-year group all-cause mortality, breast cancer-specific mortality, and the incidence of contralateral breast cancer were reduced, compared with those among 2129 patients randomized in the 2-year group, but the incidence of endometrial cancer was increased. In addition, mortality from coronary heart disease was statistically significantly reduced in the 5-year group, compared with that in the 2-year group (hazard ratio = 0.67, 95% confidence interval = 0.47 to 0.94; P = .022 [two-sided Wald test]). Ten years after surgery, 2.1% of the patients in the 5-year group and 3.5% of those in the 2-year group had died from coronary heart disease. No statistically significant increases in mortality from other heart diseases, cerebrovascular diseases, or other vascular diseases were observed.

Myocardial infarction risk and tamoxifen therapy for breast cancer

Tamoxifen prevents recurrence after breast cancer and breast cancer among high-risk women, and may prevent myocardial infarction (MI). To assess the impact of tamoxifen on MI risk, we conducted a case-control study of first MI after breast cancer nested among women diagnosed with breast cancer, while enrolled in a health maintenance organisation from 1980 to 2000. We obtained information on breast cancer treatment and MI risk factors through medical record reviews and interviews. Data were analysed using conditional logistic regression. Of 11,045 women with breast cancer, 134 met MI criteria and were matched to two MI-free control subjects on year of birth and breast cancer diagnosis. After adjusting for smoking, hypertension and diabetes, tamoxifen was unassociated with MI (odds ratio (OR)=1.2, 95% confidence interval (CI)=0.7-1.9). Duration, cumulative dose and recency of use were not associated with MI. Radiation therapy was associated with MI (OR=2.0, 95% CI=1.1-3.5), an association that varied slightly but not statistically significantly by tamoxifen use (radiation with tamoxifen, OR=2.0, 95% CI=0.9-4.4; radiation without tamoxifen, OR=2.9, 95% CI=1.2-7.5). Tamoxifen treatment for breast cancer does not appear to increase or decrease MI risk, although radiation therapy appears to increase MI risk.

Toremifene and tamoxifen are equally effective for early-stage breast cancer: first results of International Breast Cancer Study Group Trials 12-93 and 14-93

BACKGROUND

Toremifene is a chlorinated derivative of tamoxifen, developed to improve its risk-benefit profile. The International Breast Cancer Study Group (IBCSG) conducted two complementary randomized trials for peri- and postmenopausal patients with node-positive breast cancer to compare toremifene versus tamoxifen as the endocrine agent and simultaneously investigate a chemotherapy-oriented question. This is the first report of the endocrine comparison after a median follow-up of 5.5 years.

PATIENTS AND METHODS

1035 patients were available for analysis: 75% had estrogen receptor (ER)-positive primary tumors, the median number of involved axillary lymph nodes was three and 81% received prior adjuvant chemotherapy.

RESULTS

Toremifene and tamoxifen yielded similar disease-free (DFS) and overall survival (OS): 5-year DFS rates of 72% and 69%, respectively [risk ratio (RR)=0.95; 95% confidence interval (CI)=0.76-1.18]; 5-year OS rates of 85% and 81%, respectively (RR = 1.03; 95% CI = 0.78-1.36). Similar outcomes were observed in the ER-positive cohort. Toxicities were similar in the two treatment groups with very few women (<1%) experiencing severe thromboembolic or cerebrovascular complications. Quality of life results were also similar. Nine patients developed early stage endometrial cancer (toremifene, six; tamoxifen, three).

CONCLUSIONS

Toremifene is a valid and safe alternative to tamoxifen in postmenopausal women with endocrine-responsive breast cancer.

Tamoxifen-treated breast carcinoma patients and the risk of acute myocardial infarction and newly-diagnosed angina

BACKGROUND

It is known that tamoxifen therapy favorably affects blood cholesterol levels and other cardiovascular disease risk factors; however, to our knowledge, few studies to date have reported a lower risk of heart disease for breast carcinoma patients who are treated with tamoxifen.

METHODS

A nested, matched, case-control study design was used with data from the General Practice Research Database to examine whether patients with breast carcinoma who had been treated with tamoxifen were at reduced risk of having a first acute myocardial infarction (MI) or of developing angina compared with unexposed women. All women between age 30 years and age 85 years who had been diagnosed with breast carcinoma and treated with tamoxifen, or who had been diagnosed with carcinoma of the bladder or colorectum, or nonmelanoma skin cancer between January 1991 and December 1999 were identified. From this population, all women were identified who had newly diagnosed acute MI or angina that occurred at least 1 year after their cancer diagnosis. Four female control participants were matched to each case based on age (+/- 1 year), date of MI or angina diagnosis (corresponding date for matched controls), and date of cancer diagnosis (+/- 6 months). Odds ratios (ORs) and 95% confidence intervals (95% CIs) were generated using conditional logistic regression, controlling for the matching factors, and adjusting for important risk factors, including body mass index, use of hormone replacement therapy, smoking status, and treated hypertension.

RESULTS

Current users of tamoxifen had a reduced rate ratio of acute MI or angina (adjusted OR, 0.4; 95% CI, 0.2-0.7) compared with nonusers. The effect persisted with increasing cumulative dose and length of use.

CONCLUSIONS

The treatment of breast carcinoma with tamoxifen was found to reduce a woman's risk of acute MI or angina during the 5 years of recommended therapy.