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

Aromatase inhibition increases blood pressure and markers of renal injury in female rats

Aromatase is a monooxygenase that catalyzes the rate-limiting step of estrogen biosynthesis from androgens. Aromatase inhibitors are widely used for the treatment of patients with hormone receptor-positive breast cancer. However, the effects of aromatase inhibitors on cardiovascular and renal health in females are understudied. Given that estrogen is protective against cardiovascular and kidney diseases, we hypothesized that aromatase inhibition elevates blood pressure and induces kidney injury in female Sprague-Dawley rats. Twelve-week-old female rats were implanted with radiotelemetry transmitters to continuously monitor blood pressure. After baseline blood pressure recording, rats were randomly assigned to treatment with the aromatase inhibitor anastrozole (ASZ) or vehicle (Veh) in drinking water. Twenty days after treatment initiation, rats were shifted from a normal-salt (NS) diet to a high-salt (HS) diet for an additional 40 days. Rats were euthanized 60 days after treatment initiation. Body weight increased in both groups over the study period, but the increase was greater in the ASZ-treated group than in the Veh-treated group. Mean arterial pressure increased in ASZ-treated rats during the NS and HS diet phases but remained unchanged in Veh-treated rats. In addition, urinary excretion of albumin and kidney injury marker-1 and plasma urea were increased in response to aromatase inhibition. Furthermore, histological assessment revealed that ASZ treatment increased morphological evidence of renal tubular injury and proximal tubular brush border loss. In conclusion, chronic aromatase inhibition in vivo with ASZ increases blood pressure and markers of renal proximal tubular injury in female Sprague-Dawley rats, suggesting an important role for aromatization in the maintenance cardiovascular and renal health in females.NEW & NOTEWORTHY Aromatase enzyme catalyzes the rate-limiting step in estrogen biosynthesis. Aromatase inhibitors are clinically used for the treatment of patients with breast cancer; however, the impact of inhibiting aromatization on blood pressure and renal function is incompletely understood. The present findings demonstrate that systemic anastrozole treatment increases blood pressure and renal tubular injury markers in female rats fed a high-salt diet, suggesting an important role for aromatization in preserving cardiovascular and renal health in females.

Are aromatase inhibitors associated with higher myocardial infarction risk in breast cancer patients? A Medicare population-based study

BACKGROUND

Theoretically, the estrogen deprivation induced by aromatase inhibitors (AIs) might cause ischemic heart disease, but empiric studies have shown mixed results. We aimed to compare AIs and tamoxifen with regard to cardiovascular events among older breast cancer patients outside of clinical trials. We hypothesized that AIs increase the risk of myocardial infarction.

METHODS

We identified women age ≥67 years diagnosed with breast cancer from June 30, 2006 to June 1, 2008 in the surveillance, epidemiology, and end results (SEER)-Medicare database, treated with either tamoxifen or an AI, and followed through December 31, 2012. To compare myocardial infarction (MI) risk for the treatment groups of AIs vs tamoxifen, we developed and assigned stabilized probability of treatment weights and used the Fine and Gray model for time to MI with death not related to MI as a competing risk.

RESULTS

Of the cohort of 5648 women, 4690 were treated with AIs and 958 with tamoxifen; a total of 251 patients developed MI, and 22 patients died of MI during the study period while 476 died of other causes. The hazard for MI was not significantly different between AI vs tamoxifen groups (HR = 1.01, 95% CI 0.72-1.42), after adjusting for the following known MI risk factors at the start of adjuvant therapy: diabetes, ischemic heart disease, congestive heart failure, MI, and peripheral vascular disease.

CONCLUSIONS

In this SEER-Medicare-based population study, there were no significant differences in the risk of MI between AI and tamoxifen users after adjustment for known risk factors.

Incidence of comorbidities in women with breast cancer treated with tamoxifen or an aromatase inhibitor: an Australian population-based cohort study

Background

The development of comorbidities has become increasingly relevant with longer-term cancer survival.

Objective

To assess the pattern of comorbidities among Australian women with breast cancer treated with tamoxifen or an aromatase inhibitor.

Design

Retrospective cohort study using Pharmaceutical Benefits Scheme (PBS) data (10% sample) from January 2003 to December 2014. Dispensing claims data were used to identify comorbidities and classified with the Rx-Risk-V model. The breast cancer cohort had tamoxifen or an aromatase inhibitor dispensed between 2004 and 2011 with no switching between types of endocrine therapy. Comparisons were made between the breast cancer cohort and specific control groups (age- and sex-matched at 1:10 ratio without any dispensing of anti-neoplastic agents during the study period) for the development of five individual comorbidities over time using Cox regression models.

Results

Women treated with tamoxifen had a higher incidence of cardiovascular conditions, diabetes, and pain or pain-inflammation, but a lower incidence of hyperlipidaemia compared with non-cancer control groups, as indicated by PBS data. Women treated with aromatase inhibitors were more likely to develop cardiovascular conditions, osteoporosis, and pain or pain-inflammation compared with non-cancer control groups. The risks of hyperlipidaemia and osteoporosis were significantly lower among tamoxifen users compared with aromatase inhibitor users.

Conclusions

Women with hormone-dependent breast cancer treated with an endocrine therapy had a higher risk of developing specified comorbid conditions than women without cancer, with different comorbidity profiles for those on tamoxifen versus aromatase inhibitors. Further research into the causes and mechanism of development and management of comorbidities after cancer is needed.

Comparison of Changes in the Lipid Profiles of Eastern Chinese Postmenopausal Women With Early-Stage Breast Cancer Treated With Different Aromatase Inhibitors: A Retrospective Study

Cardiovascular morbidity is closely associated with serum lipid level. We aimed to investigate the effects of different aromatase inhibitors, including letrozole, anastrozole, and exemestane, on the lipid profile of eastern Chinese breast cancer patients. We evaluated a retrospective cohort of eastern Chinese postmenopausal women with early-stage breast cancer who received aromatase inhibitors. A total of 116 postmenopausal women with early-stage breast cancer without prior cardiovascular disease were included. Lipid changes at 3, 6, 12, and 24 months were compared across the endocrine therapy categories. Our data demonstrated that exemestane treatment significantly decreased triglyceride level compared with letrozole after 24 months. However, the aromatase inhibitors had almost equivalent impacts on high-density liportein cholesterol, low-density lipoprotein cholesterol, and triglyceride after long-term aromatase inhibitor treatment. As a small-size retrospective study, our data do not support a judgment about whether one AI or another carries more or less risk in terms of lipid disorders in eastern Chinese breast cancer patients. The exact effects need further randomized, controlled trials to investigate.

Contemporary Breast Radiotherapy and Cardiac Toxicity

Long-term cardiac effects are an important component of survivorship after breast radiotherapy. The pathophysiology of cardiotoxicity, history of breast radiotherapy, current methods of cardiac avoidance, modern outcomes, context of historical outcomes, quantifying cardiac effects, and future directions are reviewed in this article. Radiation-induced oxidative stress induces proinflammatory cytokines and is a process that potentiates late effects of fibrosis and intimal proliferation in endothelial vasculature. Breast radiation therapy has changed substantially in recent decades. Several modern technologies exist to improve cardiac avoidance such as deep inspiration breath hold, gating, accelerated partial breast irradiation, and use of modern 3-dimensional planning. Modern outcomes may vary notably from historical long-term cardiac outcomes given the differences in cardiac dose with modern techniques. Methods of quantifying radiation-related cardiotoxicity that correlate with future cardiac risks are needed with current data exploring techniques such as measuring computed tomography coronary artery calcium score, single-photon emission computed tomography imaging, and biomarkers. Placing historical data, dosimetric correlations, and relative cardiac risk in context are key when weighing the benefits of radiotherapy in breast cancer control and survival. Estimating present day cardiac risk in the modern treatment era includes challenges in length of follow-up and the use of confounding cardiotoxic agents such as evolving systemic chemotherapy and targeted therapies. Future directions in both multidisciplinary management and advancing technology in radiation oncology may provide further improvements in patient risk reduction and breast cancer survivorship.

Long-term breast cancer survivors' symptoms and morbidity: differences by sexual orientation?

PURPOSE

Because little is known about morbidity and symptoms among sexual minority women with breast cancer, that is, lesbian or bisexual-identified women, and women with a preference for a woman partner, we examined differences by sexual orientation in long-term survivors' symptoms and morbidity, considering arm morbidity, systemic therapy side effects, hypertension, and number of comorbidities.

METHODS

From a state cancer registry, we recruited 257 heterosexual and 69 sexual minority women (SMW) with a diagnosis of primary, nonmetastatic breast cancer. To increase the number of SMW, we used convenience recruitment methods and obtained an additional 112 SMW who fit the same eligibility criteria as the registry-derived sample. Using a telephone survey, we collected demographic and self-reported data on arm morbidity and systematic therapy side effects, using the European Organization for Research and Treatment of Cancer Quality of Life scale, QLQ-BR23 and a comorbidity measure developed for breast cancer survivors.

RESULTS

Sexual orientation was more strongly associated with arm morbidity and systemic side effects than with high blood pressure and comorbidities. Sexual orientation related indirectly to systemic side effects and arm morbidity through cancer treatments and some demographic factors.

CONCLUSIONS

Our finding that SMW respond more negatively to certain cancer treatments compared to heterosexual women suggests an opportunity to intervene with education and support for SMW breast cancer survivors for whom these life-saving treatments are necessary.

IMPLICATIONS FOR CANCER SURVIVORS

Because breast cancer survivors are at risk for multiple severe and persistent symptoms, assessing such symptoms is an important aspect of survivorship care. Cultural differences in perception of symptoms, communication issues, cultural barriers to reporting of symptoms, and different cultural norms about expressing pain or impairments have been established by studies. Knowledge about differences in impairment and symptoms by sexual orientation will help providers' efforts to provide high quality care to breast cancer survivors and may enhance cancer survivorship.

Putting the cardiovascular safety of aromatase inhibitors in patients with early breast cancer into perspective: a systematic review of the literature

In the adjuvant setting, the third-generation aromatase inhibitors (AIs) anastrozole, letrozole and exemestane are recommended at some point during treatment, either in the upfront, switch after tamoxifen or extended treatment setting after tamoxifen in postmenopausal patients with hormone receptor-positive early breast cancer. AIs have demonstrated superior disease-free survival and overall benefit-to-risk profiles compared with tamoxifen. Potential adverse events, including cardiovascular (CV) side effects, should be considered in the long-term management of patients undergoing treatment with AIs. AIs reduce estrogen levels by inhibiting the aromatase enzyme, thus reducing the levels of circulating estrogen. This further reduction in estrogen levels may potentially increase the risk of developing CV disease. This systematic review evaluated published clinical data for changes in plasma lipoproteins and ischaemic CV events during adjuvant therapy with AIs in patients with hormone receptor-positive early breast cancer. The electronic databases MEDLINE, EMBASE, Derwent Drug File and BIOSIS were searched to identify English-language articles published from January 1998 to 15 April 2011 that reported data on AIs and plasma lipoproteins and/or ischaemic CV events. Overall, available data did not show any definitive patterns or suggest an unfavourable effect of AIs on plasma lipoproteins from baseline to follow-up assessment in patients with hormone receptor-positive early breast cancer. Changes that occurred in plasma lipoproteins were observed soon after initiation of AI therapy and generally remained stable throughout the studies. Available data do not support a substantial risk of ischaemic CV events associated with adjuvant AI therapy; however, studies with longer follow-up are required to better characterize the CV profile of AIs.

Cardiotoxicity of molecularly targeted agents

Cardiac toxicity of molecularly targeted cancer agents is increasingly recognized as a significant side effect of chemotherapy. These new potent therapies may not only affect the survival of cancer cells, but have the potential to adversely impact normal cardiac and vascular function. Unraveling the mechanisms by which these therapies affect the heart and vasculature is crucial for improving drug design and finding alternative therapies to protect patients predisposed to cardiovascular disease. In this review, we summarize the classification and side effects of currently approved molecularly targeted chemotherapeutics.

Patient and physician perceptions on continuing aromatase inhibitors beyond the 5-year mark

Aromatase inhibitors (AIs) have been shown to improve disease-free survival and in certain cases, overall survival in the treatment of postmenopausal women with hormone receptor positive early breast cancer. Trials are ongoing to determine if AI therapy should be continued for patients who have already completed 5 years of AI treatment. The objective of this study was to assess the minimum disease-free and overall survival benefit acceptable to physicians and to women undergoing AI therapy to continue treatment beyond 5 years. A self-administered survey was completed by women with stage I-III breast cancer, who were undergoing adjuvant AI therapy for at least 1 year. The survey assessed relevant cancer-related, treatment, social and comorbid factors, and FACT-ES (V4). Minimum acceptable treatment benefit was denoted as a percentage decrease in cancer recurrence risk, and percentage increase in survival at 5 years. Medical oncologists (MOs) treating breast cancer across Canada were also surveyed. A total of 153 patients were surveyed; median age was 60, 51% had node-negative disease, 89% had prior radiation therapy, 61% had prior chemotherapy, and 59% had prior tamoxifen therapy. Mean duration of AI therapy was 31 months. Approximately 30% of women required a 5-year survival benefit of less than 1%, and 27.5% needed a decrease in risk of recurrence of less than 1% to continue an AI beyond the initial 5 years. In contrast, 45% of the 40 surveyed MOs required a 5-year survival benefit of at least 1-2%, and 37.5% preferred a decrease in recurrence risk of 2-5% to prescribe an AI for an additional 5 years. There was a significant correlation between severity of endocrine symptoms experienced on AIs and an increased minimum survival benefit required for women to continue therapy (r = 0.18, p = 0.036). Patients were willing to continue on AIs for smaller treatment benefits than physicians would prefer to prescribe them beyond 5 years. Patient preference to continue on AIs correlated somewhat to the severity of AI-related side effects.

Matters of the heart: cardiac toxicity of adjuvant systemic therapy for early-stage breast cancer

Breast cancer remains the most common malignancy in women. Since the late 1980s, significant advances have been made in the treatment of this cancer. Those advances, particularly the ones in the adjuvant setting, have led to declines in the mortality associated with breast cancer. But another result has been treatments that are more complex and that potentially carry more toxicity. One key toxicity related to the adjuvant therapy of breast cancer is cardiac toxicity. Some of the agents commonly used for the treatment of breast cancer, including anthracyclines, trastuzumab, and possibly even aromatase inhibitors, have been associated with cardiac toxicity. The present article reviews the current understanding of cardiac toxicity risk and strategies to minimize cardiac morbidity associated with cytotoxic chemotherapy, trastuzumab therapy, and hormonal therapy with aromatase inhibitors for early-stage breast cancer.

The impact of an aromatase inhibitor on body composition and gonadal hormone levels in women with breast cancer

Aromatase inhibitors (AIs) have become the standard adjuvant therapy of postmenopausal breast cancer survivors. AIs induce a reduction of bioavailable estrogens by inhibiting aromatase, which would be expected to induce alterations in body composition, more extensive than induced by menopause. The objectives are to examine the impact of AIs on (1) DXA-scan derived body composition and (2) gonadal hormone levels. This is a sub-analysis of a 2-year double-blind, placebo-controlled, randomized trial of 82 women with nonmetastatic breast cancer, newly menopausal following chemotherapy, who were randomized to risedronate (35 mg once weekly) versus placebo, and stratified for their usage of AI versus no AI. Outcomes included DXA-scan derived body composition and gonadal hormone levels. As a group, total body mass increased in women over 24 months. Women on AIs gained a significant amount of lean body mass compared to baseline as well as to no-AI users (P < 0.05). Women not on an AI gained total body fat compared to baseline and AI users (P < 0.05). Free testosterone significantly increased and sex hormone binding globulin (SHBG) significantly decreased in women on AIs compared to no AIs at 24 months (P < 0.01) while total estradiol and testosterone levels remained stable. Independent of AI usage, chemotherapy-induced postmenopausal breast cancer patients demonstrated an increase of total body mass. AI users demonstrated maintenance of total body fat, an increase in lean body mass and free testosterone levels, and a decrease in SHBG levels compared to no-AI users. The mechanisms and implications of these changes need to be studied further.

Expert opinion on the use of anthracyclines in patients with advanced breast cancer at cardiac risk

Anthracyclines are considered to be among the most active agents for the treatment of breast cancer. However, their use is limited by cumulative, dose-related cardiotoxicity. Such cardiotoxicity results in a permanent loss of cardiac myocytes and a progressive reduction in cardiac function following each subsequent dose of anthracycline. Initially, damage to the heart is subclinical; however, increasingly impaired cardiac function can result in cardiovascular symptoms, with serious cardiac injury resulting in chronic heart failure. Since the early detection and treatment of cardiotoxicity can reduce its clinical effects, it is important that oncologists are aware of these adverse effects and manage them appropriately. This review examines the risk factors for anthracycline-associated cardiotoxicity and offers recommendations on strategies to reduce the cardiotoxicity of anthracyclines in the management of patients with advanced breast cancer.

Do adjuvant aromatase inhibitors increase the cardiovascular risk in postmenopausal women with early breast cancer? Meta-analysis of randomized trials

BACKGROUND

Despite the advantages from using aromatase inhibitors (AIs) compared with tamoxifen for early breast cancer, an unexpectedly greater number of grade 3 and 4 cardiovascular events (CVAE) (as defined by National Cancer Institute of Canada-Common Toxicity Criteria [version 2.0] was demonstrated.

METHODS

Phase 3 randomized clinical trials (RCTs) comparing AI with tamoxifen in early breast cancer were considered eligible for this review. The event-based risk ratios (RRs) with 95% confidence intervals (95% CIs) were derived, and a test of heterogeneity was applied. Finally, absolute differences (ADs) in event rates and the number of patients needed to harm 1 patient (NNH) were determined.

RESULTS

Seven eligible RCTs (19,818 patients) reported CVAE results. When considering all RCTs, the AD of the primary endpoint (CVAE) between the 2 arms (0.52%), tamoxifen versus AI, was statistically significant (RR, 1.31; 95% CI, 1.07-1.60; P= .007). This translated into an NNH value of 189 patients; when only third-generation AIs were considered, the difference (0.57%) remained significant (RR, 1.34; 95% CI, 1.09-1.63; P= .0038). Thromboembolic events were significantly more frequent in the tamoxifen arm, regardless of the strategy adopted (RR, 0.53; 95% CI, 0.42-0.65; P< .0001), without significant heterogeneity (P= .21). An AD of 1.17% and an NNH value of 85 patients were observed.

CONCLUSIONS

According to the results from this meta-analysis, the risk of grade 3 and 4 CVAEs in patients who were receiving AIs was higher compared with the risk in patients who were receiving tamoxifen, and the difference reached statistical significance. However, the AD was relatively low, and from 160 to 180 patients had to be treated to produce 1 event.