Effects of tamoxifen on serum lipid and apolipoprotein levels in postmenopausal patients with breast cancer

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.

Cancer Treatment-Related Cardiovascular Toxicity in Gynecologic Malignancies: JACC: CardioOncology State-of-the-Art Review

Improvements in early detection and treatment of gynecologic malignancies have led to an increasing number of survivors who are at risk of long-term cardiac complications from cancer treatment. Multimodality therapies for gynecologic malignancies, including conventional chemotherapy, targeted therapeutics, and hormonal agents, place patients at risk of cancer therapy-related cardiovascular toxicity during and following treatment. Although the cardiotoxicity associated with some female predominant cancers (eg, breast cancer) have been well recognized, there has been less recognition of the potential adverse cardiovascular effects of anticancer therapies used to treat gynecologic malignancies. In this review, the authors provide a comprehensive overview of the cancer therapeutic agents used in gynecologic malignancies, associated cardiovascular toxicities, risk factors for cardiotoxicity, cardiac imaging, and prevention strategies.

Breast Cancer and the Cardiovascular Disease: A Narrative Review

Breast cancer is the most common malignancy affecting females worldwide and is also among the top causes of all cancer-related deaths. Cardiovascular disease (CVD) is known to have the highest rate of mortality in women. There are several risk factors for both CVD and breast cancer that overlap, such as diet, smoking, and obesity, and also the current breast cancer treatment has a significant detrimental effect on cardiovascular health in general. Patients with exposure to potentially cardiotoxic treatments, including anthracyclines, trastuzumab, and radiation therapy, are more likely to develop CVD than non-cancer controls. Early detection and treatment may reduce the risk of the development of cardiac morbidity and mortality and would increase the number of breast cancer survivors. This article provides a comprehensive overview of breast cancer, identifies shared risk factors among breast cancer and CVD, and the cardiotoxic effects of therapy. It also reviews possible prevention and treatment of CVD in breast cancer patients and reviews literature about chemoprevention of cardiac disease in the setting of breast cancer treatment.

The effect of tamoxifen on the lipid profile in women: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND AND AIM

The effect of tamoxifen administration on serum lipids in females remains unclear. The studies which have explored this topic have produced conflicting results, probably due to discrepancies in the length of the intervention, differences in baseline variables or other factors. To answer this research question, we decided to conduct this systematic review and meta-analysis to assess the effects of tamoxifen on the lipid profile in women.

METHODS

A comprehensive search was conducted in Web of Science, Scopus, PubMed/Medline and Embase, from the inception of these databases up to June 2021. We used a random effects meta-analysis to generate the combined results.

RESULTS

The overall findings were generated from 18 eligible trials. As compared to placebo, tamoxifen led to a notable reduction of the total cholesterol (TC) (WMD: -23.03 mg/dL, 95% CI: -25.94 to -20.12, P˂0.001), and the low-density lipoprotein-cholesterol (LDL-C) (WMD: -18.68 mg/dL, 95% CI: -24.31 to -13.04, P˂0.001). However, tamoxifen did not alter triglycerides (TG) concentrations (WMD: +1.06 mg/dL, 95% CI: -11.08 to 13.20, P = 0.864) significantly. A pronounced reduction of the high-density lipoprotein-cholesterol (HDLC) was noted in the RCTs with a duration of ≤52 weeks (WMD: -2.06 mg/dL) and when tamoxifen was administered in participants with a BMI ≥25 kg/m² (WMD: -1.42 mg/dL). Notable reductions in TC (WMD: -23.57 mg/dL) and LDL-C (WMD: -19.21 mg/dL) was detected when the dose of tamoxifen was ≥20 mg/day. Moreover, a significant reduction of TC (WMD: -20.23 mg/dL) and LDL-C (WMD: -24.13 mg/dL) was observed in the RCTs with a duration of ≤52 weeks.

CONCLUSION

Tamoxifen can alter the lipid profile in females, particularly by decreasing TC, LDL-C and HDLC. Tamoxifen can further reduce TC and LDL-C if the dose of administration is ≥20 mg/day, the treatment duration is ≤52 weeks and if it prescribed in subjects with dyslipidemia.

Circulating lipids and breast cancer prognosis in the Malmö diet and cancer study

Purpose

Examine the association between circulating lipids and breast cancer outcomes in patients enrolled in the Malmö Diet and Cancer Study (MDCS).

Patients and methods

Circulating lipid levels were measured in blood sampled upon enrollment in the female MDCS cohort (N = 17,035). We identified all MDCS participants with incident invasive breast cancer diagnosed between 1991 and 2014. Follow-up time began at breast cancer diagnosis and continued until the first event of breast cancer recurrence, death, emigration, or 5 years of follow-up. We estimated the incidence rates of recurrence at 5 years and fit Cox regression models to compute crude and adjusted hazard ratios (HRs) with 95% confidence intervals (95% CI) of breast cancer recurrence as well as all-cause mortality according to cohort-specific tertiles of apolipoprotein A-1 (Apo A-1) and apolipoprotein B (Apo B).

Results

We enrolled 850 eligible patients. During the 5 years of follow-up, 90 invasive breast cancer recurrences were diagnosed over 3807 person-years. In multivariable analyses, high baseline levels of Apo B were associated with an increased rate of recurrence (tertile 3 vs. 1, HR = 2.30 [95% CI 1.13–4.68]). However, high baseline levels of Apo B were not associated with all-cause mortality (tertile 3 vs. 1, HR = 1.23 [95% CI 0.68–2.25]). We observed no associations between levels of Apo A-1 and recurrence (tertile 3 vs. 1, HR = 1.34 [95% CI 0.70–2.58]) or all-cause mortality (tertile 3 vs. 1, HR = 1.12 [95% CI 0.61–2.05]).

Conclusion

High pre-diagnostic levels of Apo B were associated with an increased risk of recurrence among breast cancer patients. Circulating Apo A-1 was not associated with breast cancer outcomes.

Endocrine therapy use and cardiovascular risk in postmenopausal breast cancer survivors

Objective

Examine the effect of tamoxifen and aromatase inhibitors (AIs) on the risk of 12 clinically relevant cardiovascular outcomes in postmenopausal female breast cancer survivors.

Methods

We carried out two prospective cohort studies among postmenopausal women with breast cancer in UK primary care and hospital data (2002–2016) and US Surveillance, Epidemiology and End Results-Medicare data (2008–2013). Using Cox adjusted proportional hazards models, we compared cardiovascular risks between AI and tamoxifen users; and in the USA, between users of both drug classes and women receiving no endocrine therapy.

Results

10 005 (UK) and 22 027 (USA) women with postmenopausal breast cancer were included. In both countries, there were higher coronary artery disease risks in AI compared with tamoxifen users (UK age-standardised incidence rate: 10.17 vs 7.51 per 1000 person-years, HR: 1.29, 95% CI 0.94 to 1.76; US age-standardised incidence rate: 36.82 vs 26.02 per 1000 person-years, HR: 1.29, 95% C I1.06 to 1.55). However, comparisons with those receiving no endocrine therapy (US data) showed no higher risk for either drug class and a lower risk in tamoxifen users (age-standardised incidence rate tamoxifen vs unexposed: 26.02 vs 35.19 per 1000 person-years, HR: 0.74, 95% 0.60 to 0.92; age-standardised incidence rate AI vs unexposed: 36.82 vs 35.19, HR: 0.96, 95% CI 0.83 to 1.10). Similar patterns were seen for other cardiovascular outcomes (arrhythmia, heart failure and valvular heart disease). As expected, there was more venous thromboembolism in tamoxifen compared with both AI users and those unexposed.

Conclusions

Higher risks of several cardiovascular outcomes among AI compared with tamoxifen users appeared to be driven by protective effects of tamoxifen, rather than cardiotoxic effects of AIs.

Estrogen-mediated protection against coronary heart disease: The role of the Notch pathway

Estrogen regulates a plethora of biological processes, under physiological and pathological conditions, by affecting key pathways involved in the regulation of cell proliferation, fate, survival and metabolism. The Notch receptors are mediators of communication between adjacent cells and are key determinants of cell fate during development and in postnatal life. Crosstalk between estrogen and the Notch pathway intervenes in many processes underlying the development and maintenance of the cardiovascular system. The identification of molecular mechanisms underlying the interaction between these types of endocrine and juxtacrine signaling are leading to a deeper understanding of physiological conditions regulated by these steroid hormones and, potentially, to novel therapeutic approaches to prevent pathologies linked to reduced levels of estrogen, such as coronary heart disease, and cardiotoxicity caused by hormone therapy for estrogen-receptor-positive breast cancer.

Acquired resistance to aromatase inhibitors: where we stand!

Aromatase inhibitors (AIs) are one of the principal therapeutic approaches for estrogen receptor-positive (ER⁺) breast cancer in postmenopausal women. They block estrogen biosynthesis through aromatase inhibition, thus preventing tumour progression. Besides the therapeutic success of the third-generation AIs, acquired resistance may develop, leading to tumour relapse. This resistance is thought to be the result of a change in the behaviour of ER in these breast cancer cells, presumably by PI3K/AKT pathway enhancement along with alterations in other signalling pathways. Nevertheless, biological mechanisms, such as apoptosis, autophagy, cell cycle modulation and activation of androgen receptor (AR), are also implicated in acquired resistance. Moreover, clinical evidence demonstrated that there is a lack of cross-resistance among AIs, although the reason is not fully understood. Thus, there is a demand to understand the mechanisms involved in endocrine resistance to each AI, since the search for new strategies to surpass breast cancer acquired resistance is of major concern.

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.

Cardiovascular Disease and Breast Cancer: Where These Entities Intersect: A Scientific Statement From the American Heart Association

Cardiovascular disease (CVD) remains the leading cause of mortality in women, yet many people perceive breast cancer to be the number one threat to women's health. CVD and breast cancer have several overlapping risk factors, such as obesity and smoking. Additionally, current breast cancer treatments can have a negative impact on cardiovascular health (eg, left ventricular dysfunction, accelerated CVD), and for women with pre-existing CVD, this might influence cancer treatment decisions by both the patient and the provider. Improvements in early detection and treatment of breast cancer have led to an increasing number of breast cancer survivors who are at risk of long-term cardiac complications from cancer treatments. For older women, CVD poses a greater mortality threat than breast cancer itself. This is the first scientific statement from the American Heart Association on CVD and breast cancer. This document will provide a comprehensive overview of the prevalence of these diseases, shared risk factors, the cardiotoxic effects of therapy, and the prevention and treatment of CVD in breast cancer patients.

Extended adjuvant endocrine therapy - A standard to all or some?

Patients with estrogen receptor-positive (ER +) early breast cancer (EBC) are at a continuous risk for distant relapse despite 5 years of standard endocrine therapy, even after 10-15 years after primary diagnosis. Hence, large randomized clinical trials were conducted to evaluate the role of extended endocrine treatment (ET) with the primary goal to prevent or at least delay distant relapse. Two very large trials of extended tamoxifen (TAM), the ATLAS and the aTTom trial, proved the efficacy of prolonged TAM particularly important after 10 years due to the carry-over effect of the five initial years. Additionally, the extended use of AIs after 5 years of tamoxifen, also proved to be efficacious in preventing late distant relapses. For letrozole (LET) it was shown in the MA.17 trial that it also improves overall survival (OS) in node-positive BC patients. There are many options and still unanswered questions related to extended ET, which are discussed in this review. The most important issue in deciding prolonged duration of ET is undoubtfully how to identify ER+ patients who benefit most from this approach. With this purpose, not only classical pathological factors have been studied, but also molecular profiles of individual tumors, which might help us in the near future to better tailor ET. Not only efficacy, but also toxicity of such prolonged treatment is essential for optimal use, particularly maintained compliance in a routine clinical practice. These issues are discussed in this review.

Tamoxifen regulation of sphingolipid metabolism--Therapeutic implications

Tamoxifen, a triphenylethylene antiestrogen and one of the first-line endocrine therapies used to treat estrogen receptor-positive breast cancer, has a number of interesting, off-target effects, and among these is the inhibition of sphingolipid metabolism. More specifically, tamoxifen inhibits ceramide glycosylation, and enzymatic step that can adventitiously support the influential tumor-suppressor properties of ceramide, the aliphatic backbone of sphingolipids. Additionally, tamoxifen and metabolites N-desmethyltamoxifen and 4-hydroxytamoxifen, have been shown to inhibit ceramide hydrolysis by the enzyme acid ceramidase. This particular intervention slows ceramide destruction and thereby depresses formation of sphingosine 1-phosphate, a mitogenic sphingolipid with cancer growth-promoting properties. As ceramide-centric therapies are becoming appealing clinical interventions in the treatment of cancer, agents like tamoxifen that can retard the generation of mitogenic sphingolipids and buffer ceramide clearance via inhibition of glycosylation, take on new importance. In this review, we present an abridged, lay introduction to sphingolipid metabolism, briefly chronicle tamoxifen's history in the clinic, examine studies that demonstrate the impact of triphenylethylenes on sphingolipid metabolism in cancer cells, and canvass works relevant to the use of tamoxifen as adjuvant to drive ceramide-centric therapies in cancer treatment. The objective is to inform the readership of what could be a novel, off-label indication of tamoxifen and structurally-related triphenylethylenes, an indication divorced from estrogen receptor status and one with application in drug resistance.

Apolipoprotein E genetic polymorphism, serum lipoprotein levels and breast cancer risk: A case-control study

The purpose of this study was to evaluate the association between apolipoprotein E (APOE) allelic frequency, serum lipoproteins and breast cancer (BC). We conducted a nested case-control study within a cohort including 47 cases and 165 controls. Polymerase chain reaction-restriction fragment length polymorphism analyses of the APOE polymorphism were performed. In general, participants with the genotype including alleles e2 and e3 tended to have lower serum triglycerides, total cholesterol and low-density lipoprotein cholesterol levels and higher high-density lipoprotein (HDL) cholesterol levels compared to participants homozygous for the e3 allele and participants heterozygous for the e3 and e4 alleles, respectively. BC patients exhibited higher mean levels of total serum cholesterol (P=0.070), dietary fat intake (P=0.020) and dietary cholesterol intake (P=0.017) compared to control subjects. The allelic distribution between the two groups revealed that the presence of the e2 allele was positively associated with the absence of BC, whereas the e4 allele was positively associated with the BC case group (P=0.019). The distribution of the APOE genotypes was not significantly different between cases and controls (P=0.172). The concomitant presence of the e2 and e4 alleles was positively associated with the absence of BC and e4/e4 homozygosity was positively associated with BC (P=0.021). Our findings suggested that APOE polymorphism plays an important role in the development of BC, particularly when associated with higher serum triglyceride levels.

Intima-media thickness, myocardial perfusion and laboratory risk factors of atherosclerosis in patients with breast cancer treated with anthracycline-based chemotherapy

An increased incidence of complications of atherosclerosis has been noted in cancer survivors. The aim of the present study was to evaluate, in patients with breast carcinoma, the effect of antracycline-based chemotherapy on carotid intima-media thickness (IMT), myocardial perfusion, assessed by single-photon emission tomography (SPECT) and laboratory parameters associated with the risk of atherosclerosis. Thirty-six patients with breast cancer were evaluated before and after anthracycline-based chemotherapy. Retinol, alpha-tocopherol, glycosylated hemoglobin and urinary neopterin were measured by high-performance liquid chromatography. Peripheral blood cell count, D-dimers, fibrinogen, antithrombin, glucose, magnesium, creatinine, uric acid, albumin, C-reactive protein, lipoprotein (a), cholesterol, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, triglycerides, homocysteine, urinary albumin and N-acetyl-beta-D-glucosaminidase (NAG) were determined with routine methods. No significant differences were observed between patients and 16 controls. Compared to the measurement before the start of therapy, peripheral blood leukocyte and platelet count, hemoglobin, creatinine, HDL cholesterol, retinol, albumin, urinary albumin and NAG decreased, and total cholesterol, LDL cholesterol, triglycerides, neopterin and mean IMT increased significantly after the treatment. Of the 36 patients who had SPECT after treatment, perfusion defects were noted only in two cases, including the patient who had perfusion defects at baseline examination and a patient who did not have a baseline SPECT. In conclusion, a significant increase in carotid IMT, total cholesterol, LDL cholesterol, triglycerides and urinary neopterin and a decrease of peripheral blood leukocyte and platelet counts, hemoglobin, creatinine, HDL cholesterol, retinol, albumin and NAG were observed after the treatment.

Review of the ATAC study: tamoxifen versus anastrozole in early-stage breast cancer

A 5-year regimen of tamoxifen hormone therapy has historically been the recommendation for hormone receptor-positive, postmenopausal women with early-stage breast cancer. With the advent of aromatase inhibitors, there has been extensive work carried out to investigate the role of these agents in the adjuvant setting. Studies have been designed to answer whether these agents should be used upfront (instead of tamoxifen) or in conjunction (either in a switch or extended program). The Arimidex, Tamoxifen Alone or in Combination (ATAC) trial is a landmark trial that demonstrated the superiority of upfront anastrozole over tamoxifen. This article reviews the trial and discusses both the optimum timing of initiation of aromatase inhibitors and the future approach of more individualized therapy, with the detection of predictive markers.

The effects on lipid serum levels of a 2-year adjuvant treatment with exemestane after tamoxifen in postmenopausal women with early breast cancer

BACKGROUND

The third-generation aromatase inhibitor exemestane represents a new development in the treatment of estrogen-positive breast cancer. The aim of this study was to evaluate the effects on lipid profile and body composition of the shift from tamoxifen to exemestane.

METHODS

After 2-3 years of tamoxifen adjuvant treatment, 68 postmenopausal women were randomly assigned to either continue tamoxifen 20 mg/day (n = 35) or to switch to exemestane 25 mg/day (n = 33).

RESULTS

No significant changes in lipid profile were found in patients continuing on tamoxifen. In the exemestane group, serum HDL-cholesterol (HDL-C) and triglycerides (TG) decreased significantly (p < 0.01) and serum LDL-cholesterol (LDL-C) increased significantly (p < 0.05) with respect to baseline. The difference between the two groups was significant. Moreover, in the exemestane group, fat mass (FM) and fat-free mass (FFM) showed an opposite trend, which determined a progressive and significant increase in the FFM/FM ratio.

CONCLUSION

This study shows that the choice of first-line treatment or adjuvant therapy for breast cancer should also take the individual lipid and body composition profile into account.

Effects of hormonal treatment on lipids in patients with cancer

Patients with malignant disease may need hormonal therapy as primary or adjuvant treatment or for palliation. Oestrogens usually decrease serum levels of total cholesterol (TC) and low density lipoprotein cholesterol (LDL-C), increase high density lipoprotein cholesterol (HDL-C) concentration, but induce an elevation in serum triglyceride (TG) levels. Progestogens in the short-term decrease TC, LDL-C and HDL-C concentrations, and increase TG levels. In long-term treatment, progestogens usually have a small impact on lipid profile. Tamoxifen induces a decrease in TC and LDL-C levels, an increase in TG concentration, whereas either an increase, decrease or no change has been reported for HDL-C levels. Aromatase inhibitors induce an elevation, reduction or no change in lipid variables. These results depend mainly on the trial design, i.e. whether patients received prior treatment with tamoxifen or not and the duration of therapy. Gonadorelin analogues increase all lipid variables, but LDL-C alterations are usually non-significant. Anti-androgens usually decrease TC, LDL-C and HDL-C levels, whereas TG alterations vary. Information regarding the effects on lipid profile of somatostatin analogues is available almost exclusively in patients with acromegaly. In these patients somatostatin analogues usually induce no change or a decrease in TC and LDL-C levels, whereas they increase HDL-C and decrease TG serum concentrations. Oncologists should consider the lifestyle changes, and if needed hypolipidemic treatment, used to lower cardiovascular risk in non-cancer patients. Tamoxifen may rarely cause serious TG-related side effects, like acute pancreatitis.

Adjuvant Endocrine Therapy in Early Postmenopausal Breast Cancer

Five years of adjuvant tamoxifen treatment has been the gold standard for women with early hormone-responsive breast cancer. Results from two large phase III, adjuvant studies have indicated that the third-generation aro-matase inhibitors (AIs) letrozole and anastrozole offer greater protection against recurrence than tamoxifen in upfront substitution strategies in the first 5 years. Similarly, changeover to an AI (exemestane or anastrozole) after 2-3 years of tamoxifen has been more efficient to prevent recurrence than 5 years of tamoxifen. Most early breast cancer recurrences occur 5 or more years after surgery. Letrozole has been shown to offer greater protection against recurrence than placebo in the 5 years after a standard course of tamoxifen. The optimal adjuvant use (duration and sequencing) of AIs requires further investigation. Safety implications of treatment with these AIs for 5 years or more are closely monitored. The anticipated effects of estrogen deprivation on bone health may be treatable with bisphosphonates. Effects on the cardiovascular system, and other estrogen-sensitive systems such as the central nervous system, are currently examined. The AIs letrozole, anastrozole, and ex-emestane have recently replaced tamoxifen as the recommended adjuvant endocrine therapy, on the basis of greater efficacy and better tolerability.

Letrozole compared with tamoxifen for elderly patients with endocrine-responsive early breast cancer: the BIG 1-98 trial

PURPOSE

To explore potential differences in efficacy, treatment completion, and adverse events (AEs) in elderly women receiving adjuvant tamoxifen or letrozole for five years in the Breast International Group (BIG) 1-98 trial.

METHODS

This report includes the 4,922 patients allocated to 5 years of letrozole or tamoxifen in the BIG 1-98 trial. The median follow-up was 40.4 months. Subpopulation Treatment Effect Pattern Plot (STEPP) analysis was used to examine the patterns of differences in disease-free survival and incidences of AEs according to age. In addition, three categoric age groups were defined: "younger postmenopausal" patients were younger than 65 years (n = 3,127), "older" patients were 65 to 74 years old (n = 1,500), and "elderly" patients were 75 years of age or older (n = 295).

RESULTS

Efficacy results for subpopulations defined by age were similar to the overall trial results: Letrozole significantly improved disease-free survival (DFS), the primary end point, compared with tamoxifen. Elderly patients were less likely to complete trial treatment, but at rates that were similar in the two treatment groups. The incidence of bone fractures, observed more often in the letrozole group, did not differ by age. In elderly patients, letrozole had a significantly higher incidence of any grade 3 to 5 protocol-specified non-fracture AE compared with tamoxifen (P = .002), but differences were not significant for thromboembolic or cardiac AEs.

CONCLUSION

Adjuvant treatment with letrozole had superior efficacy (DFS) compared with tamoxifen in all age groups. On the basis of a small number of patients older than 75 years (6%), age per se should not unduly affect the choice of adjuvant endocrine therapy.

Do endocrine treatments for breast cancer have a negative impact on lipid profiles and cardiovascular risk in postmenopausal women?

Although cardiovascular disease occurs infrequently in premenopausal women, the incidence increases dramatically after menopause. Endocrine agents used to treat postmenopausal women with breast cancer further reduce estrogen levels and have the potential to adversely affect lipid metabolism, although the relevance of this to cardiovascular risk remains uncertain. Until recently, the standard endocrine treatment for breast cancer was tamoxifen, which appears to have a generally favorable effect on lipid parameters, although this does not translate into cardioprotective effects. The third-generation aromatase inhibitors (AIs), including anastrozole, have recently emerged as alternatives for the treatment of postmenopausal women with hormone-sensitive breast cancer. Anastrozole, currently the only AI with established long-term safety data in the adjuvant setting, results in significantly fewer thromboembolic and cerebrovascular events compared with tamoxifen, and a similar incidence of ischemic cardiovascular events. However, the effects of other AIs on lipid values are variable, and any relationship with cardiovascular events in long-term studies is currently unknown.

Comparative assessment of lipid effects of endocrine therapy for breast cancer: Implications for cardiovascular disease prevention in postmenopausal women

Cardiovascular disease (CVD) is the leading cause of death in the developed world for both men and women. Women experience significant alterations in lipid profiles during the years following menopause, including a reduction in plasma high-density lipoprotein cholesterol and an elevation of plasma low-density lipoprotein cholesterol, and are at an increased risk of CVD. These changes are due in part to the reduction in estrogen production following the onset of the menopause. Therefore, agents that have anti-estrogenic effects, such as most endocrine therapies for breast cancer, may increase the risk of CVD. Tamoxifen, historically the standard endocrine therapy, has an overall beneficial effect on lipid profiles. However, long-term data from clinical trials have failed to demonstrate a cardioprotective effect and patients treated with tamoxifen did not experience fewer cardiovascular events compared with those receiving placebo. Indeed, a number of studies have shown that tamoxifen may have a detrimental effect, with a significantly increased risk of venous thromboembolic events, pulmonary embolism and stroke. The third-generation aromatase inhibitors (AIs) have demonstrated an improvement in efficacy and tolerability over previous treatments. Since they have a different mechanism of action to tamoxifen, they are not anticipated to exert the same impact on lipid profiles. Clinical trials with anastrozole demonstrated no clinically relevant impact on lipid profiles in postmenopausal patients with advanced breast cancer. However, as lipid profiles are surrogate endpoints, the most appropriate endpoint is the incidence of cardiovascular events in long-term studies. This is of particular relevance in the treatment of early breast cancer, where endocrine agents may be used in the adjuvant setting for periods of 5 years or more. Long-term adjuvant anastrozole treatment resulted in significantly fewer thromboembolic and cerebrovascular events and a similar incidence of ischemic cardiovascular events compared with tamoxifen. The effects of the other AIs on lipid levels are variable, and any correlation with cardiovascular events is currently unknown.

Optimizing the use of aromatase inhibitors in adjuvant therapy for postmenopausal patients with hormone-responsive early breast cancer: current and future prospects

PURPOSE

Five years of tamoxifen treatment after primary surgery has had a significant impact on outcomes for women with early breast cancer, but the third-generation aromatase inhibitors (AIs) are now challenging tamoxifen as the gold standard endocrine adjuvant treatment. Results from two large, phase III, early adjuvant studies have indicated that the AIs letrozole and anastrozole offer greater protection against recurrence than tamoxifen in upfront substitution strategies in the first 5 years after surgery. Similarly, changeover to an AI (exemestane or anastrozole) after 2-3 years of tamoxifen has been shown to offer greater protection against recurrence than 5 years of tamoxifen. More than 50% of early breast cancer recurrences occur five or more years after surgery. Letrozole has been shown to offer greater protection against recurrence than placebo in the 5 years after a standard course of tamoxifen. The safety implications of treatment with these potent AIs for 5 years or more are being closely monitored. Anticipated effects of estrogen deprivation on bone health may be treatable with bisphosphonates, and this strategy is under investigation. Effects on the cardiovascular system, and other estrogen-sensitive systems such as the central nervous system, are currently unclear and further results are awaited.

CONCLUSION

Current evidence indicates that the third-generation AIs will improve outcomes for many women with early breast cancer.

Aromatase inhibitors as adjuvant treatment of breast cancer

The development of the novel, third-generation aromatase inhibitors and inactivators represents a major improvement of endocrine therapy in breast cancer. Subsequent to phase III studies revealing clinical superiority of these drugs compared to conventional therapy as second- and first-line treatment for advanced disease, several randomised studies have found these compounds, administered either as monotherapy or in sequence with tamoxifen, to improve relapse-free survival compared to tamoxifen monotherapy in the adjuvant setting. Notably, we lack data on long-term follow-up with respect to efficacy as well as side effects, and there are currently no data on head to head comparisons between the different aromatase inhibitors. Several critical issues, like influences of treatment on bone and blood lipid profiles underline the need for long-term follow-up with respect to clinical events like bone fractures and cardiovascular events. Finally, we need data on cost-utility with respect to the different strategies as well as with respect to patient age and risk profile.

Comparative effects of anastrozole, tamoxifen alone and in combination on plasma lipids and bone-derived resorption during neoadjuvant therapy in the impact trial

BACKGROUND

Estrogen has beneficial effects on lipid metabolism and bone preservation. The IMPACT trial evaluated neoadjuvant therapy with anastrozole or tamoxifen alone, or a combination. The comparative effects of these treatments on serum lipids and bone resorption were assessed.

PATIENTS AND METHODS

Non-fasting clotted blood samples were taken from 176 postmenopausal patients at baseline, 2 and 12 weeks for assessment of serum levels of estradiol, the bone resorption marker CTx and lipid profiles [total cholesterol (TC), high density lipoprotein cholesterol (HDL-C) and non-HDL cholesterol (N-HDL-C)].

RESULTS

After 12 weeks, tamoxifen was associated with a significant increase in HDL-C (26.5%), and a decrease in TC (6.5%) and N-HDL-C (12.3%). Anastrozole was associated with a significant increase in HDL-C (11.2%), and a non-significant increase in TC (2.9%) and N-HDL-C (3.4%), both of which were significantly different from tamoxifen. The combination was associated with a significant increase in HDL-C (9.4%), and a decrease in TC (10.9%) and N-HDL-C (13.9%). For tamoxifen and the combination, there were non-significant decreases in CTx compared with a significant increase (45.6%) with anastrozole. No correlation between serum estradiol and CTx was seen in any of the treatment groups.

CONCLUSION

Anastrozole did not have a detrimental effect on lipid profiles following 3 months of therapy. There was a significant increase in CTx with anastrozole in contrast to tamoxifen.

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.

Serum leptin levels are associated with tamoxifen-induced hepatic steatosis

PURPOSE

Tamoxifen, used in breast cancer treatment, may induce hepatic steatosis. It has been suggested that leptin, which has a relationship with body fat stores, may be involved in the pathogenesis of hepatic steatosis. In this study, we compared serum leptin levels in tamoxifen-treated patients with and without hepatic steatosis.

METHODS

Thirty-four women with breast cancer receiving tamoxifen were included in the study. Serum samples were obtained from the patients before and 3 months after tamoxifen therapy.

RESULTS

Increased hepatic steatosis was detected in 15 of 34 (44%) patients after 3 months of tamoxifen therapy. Serum leptin levels were found to be significantly elevated in patients with increased hepatic steatosis (37.3 +/- 17.7 to 50.5 +/- 22.4 ng/ml, p = 0.023) compared to (48.2 +/- 20.2 to 42.6 +/- 14.9 ng/ml, p > 0.05) after tamoxifen treatment.

CONCLUSION

Leptin may play a role in tamoxifen-induced hepatic steatosis. The exact mechanism involved should be investigated in further studies.

Cardiovascular effects of tamoxifen in women with and without heart disease: breast cancer prevention trial. National Surgical Adjuvant Breast and Bowel Project Breast Cancer Prevention Trial Investigators

BACKGROUND

The overall effect of prophylactic tamoxifen in women depends on the balance between the effects of the drug, which include preventing breast cancer and altering cardiovascular risk. In a recent clinical trial, postmenopausal estrogen-progestin therapy was shown to increase the risk of early cardiovascular events among women with a history of coronary heart disease (CHD). The cardiovascular effects of tamoxifen in women with and without CHD are not known. The National Surgical Adjuvant Breast and Bowel Project Breast Cancer Prevention Trial (BCPT) is the only clinical trial that provides data to assess the cardiovascular effects of tamoxifen in women with and without CHD.

METHODS

A total of 13 388 women at increased risk for breast cancer were randomly assigned in the BCPT to receive either tamoxifen (20 mg/day) or placebo. Cardiovascular follow-up was available for 13 194 women, 1048 of whom had prior clinical CHD. Fatal and nonfatal myocardial infarction, unstable angina, and severe angina were tabulated (mean follow-up: 49 months). All statistical tests were two-sided.

RESULTS

Cardiovascular event rates were not statistically significantly different between women assigned to receive tamoxifen and those assigned to receive placebo, independent of pre-existing CHD. Among women without CHD (6074 on tamoxifen versus 6072 on placebo), risk ratios (95% confidence intervals [CIs]) for tamoxifen users were 1.75 (0.44 to 8.13) for fatal myocardial infarction, 1.11 (0.55 to 2.28) for nonfatal myocardial infarction, 0.69 (0.29 to 1.57) for unstable angina, and 0.83 (0.32 to 2.10) for severe angina. In women with CHD (516 on tamoxifen versus 532 on placebo), risk ratios (95% CIs) for tamoxifen users were 0.00 (0 to 1.58) for fatal myocardial infarction, 1.25 (0.32 to 5.18) for nonfatal myocardial infarction, 2.26 (0.87 to 6.55) for unstable angina, and 1.39 (0.23 to 9.47) for severe angina. There was no evidence that the lack of association between tamoxifen and cardiovascular events was related to an early increase in risk that may have been offset by a late decrease in risk.

CONCLUSION

When used for breast cancer prevention in women with or without heart disease, tamoxifen is not associated with beneficial or adverse cardiovascular effects.

Apolipoprotein E genetic polymorphism, serum lipoproteins, and breast cancer risk

Apolipoprotein E (apoE) is a polymorphic gene involved in lipid metabolism with three common variant alleles (epsilon2, epsilon3, and epsilon4). The epsilon4 allele has been associated with elevated levels of cholesterol as well as greater risk of coronary heart disease and Alzheimer's disease. In this case-control study we examined whether apoE genotype affected the association between serum lipids and breast cancer risk. In a subset of a study in western New York, 260 women with incident, primary breast cancer and 332 community controls were interviewed and provided blood samples. Polymerase chain reaction-restriction fragment length polymorphism analyses of the apoE polymorphism were performed. Participants were classified as apoE2 (epsilon2, epsilon2 or epsilon2, epsilon3), apoE3 (epsilon3, epsilon3), or apoE4 (epsilon4, epsilon4 or epsilon4, epsilon3). No unconditional logistic regression was used to compute adjusted odds ratios (ORs) and 95% confidence intervals (CI). Compared with women with the apoE3 genotype, there were no associations with risk for women with the apoE2 (OR=1.0; 95% CI=0. 91-1.64) or apoE4 genotype (OR=0.97; 95% CI=0.63-1.54). Higher serum levels of total cholesterol, HDL cholesterol, and LDL cholesterol were not associated with risk, either in the total sample or among subgroups of women defined by apoE genotype. Women with the highest serum triglyceride levels had an increase in risk (OR=1.63; 95% CI=1. 03-2.59) compared to women with the lowest levels. This effect was not apparent among women with the apoE2 or apoE3 genotype, but much stronger among women with the apoE4 genotype (OR=4.69; 95% CI=1. 49-14.7). These data suggest that the apoE4 genotype may modify the association between serum triglycerides and breast cancer risk.

Inhibition of LDL oxidation by a new estradiol receptor modulator compound LY-139478, comparative effect with other steroids

Oxidation of low-density lipoprotein (LDL) is postulated to be essential for the development of atherosclerosis. LY-139478 is a new non-steroidal potent estrogen analog, but its effects on in vitro LDL oxidation have not been completely elucidated. We investigated the ability of LY-139478 to inhibit in vitro copper sulfate-mediated LDL oxidation using several methods, including conjugated diene (CD) accumulation, relative electrophoretic mobility on agarose gel, thiobarbituric acid-reactive substances (TBARS) assay, and superoxide anions scavenging activity. The antioxidative potential of LY-139478 was compared to testosterone (T), 17-alpha-estradiol (17alphaE), 17-beta-estradiol (17betaE), dehydroepiandrosterone (D), and dehydroepiandrosterone-3-sulfate (DS). LY-139478 was superior to 17alphaE and 17betaE in prolonging the lag phase and decreasing the slope and peak concentration of the conjugated diene accumulation, decreasing the rate of migration of LDL on agarose gel electrophoresis, and inhibiting the production of melonyldialdehyde (MDA) in the TBARS assay. T, D and DS were ineffective in all three assays. It was previously shown that when native LDL is oxidized by previously oxidized LDL (secondary oxidation) the lag phase is lost (Schnitzer et al. Free Rad Res 1995;23:137). LY-139478 was at least 15-fold more effective than 17alphaE, and 17betaE in slowing the propagation phase and reducing CD accumulation in this secondary oxidation, with 50% inhibition at 10 microM and 98% inhibition at 100 microM. However, none restored the lag phase. T, D and DS were ineffective. Superoxide anion generation was inhibited only by DS at high doses (500 microM). These results demonstrate that LY-139478 is an effective inhibitor of LDL oxidation and is superior to natural steroidal hormones, including 17betaE, in protecting against primary and secondary LDL oxidation.

Administration of long-term tamoxifen therapy modifies the plasma lipoprotein-lipid concentration and lipid transfer protein I activity in postmenopausal women with breast cancer

Tamoxifen remains one of the most effective agents in the treatment of breast cancer. However, the development of persistent side effects from chronic administration of tamoxifen remains a concern. The objective of this project was to investigate the effect of long-term tamoxifen therapy (2 years) on the plasma lipoprotein concentration and lipid transfer activity in postmenopausal women diagnosed with breast cancer. Two distinct populations of breast cancer patients were recruited for this study: postmenopausal women diagnosed with breast cancer that have never been on tamoxifen and postmenopausal women diagnosed with breast cancer that have been on tamoxifen (20 mg once daily) for 2 years (n = 18 each group). Blood was collected for total and lipoprotein cholesterol (C) and triglyceride (TG) analysis by established enzymatic assays prior to and 2 years following the initial tamoxifen dose. To determine the effect of tamoxifen administration on lipid transfer between lipoprotein fractions, lipid transfer protein (LTP I) activity was measured. A significant decrease in total and low-density lipoprotein (LDL) cholesterol levels and a moderate increase in high-density lipoprotein (HDL) triglyceride levels were observed in plasma samples from postmenopausal women with breast cancer who were administered tamoxifen for 2 years. No significant differences in total and lipoprotein C and TG plasma levels were observed in samples from women with breast cancer that never received tamoxifen. LTP I activity was significantly decreased in patients receiving tamoxifen compared to patients who never received tamoxifen. These specific tamoxifen-induced effects may be important for a number of reasons. Although the apparent decrease in total C and LDL-C levels are favorable for reducing the risk of cardiovascular disease, the elevated levels of HDL-TG have been related to the increased risk of ischemic heart disease. Furthermore, understanding how tamoxifen influences LTP I activity provides valuable insight into how the administration of tamoxifen modifies plasma lipoprotein-lipid levels.