Effects of Endocrine Therapy on Cardiovascular Diseases and Type 2 Diabetes Among Breast Cancer Survivors: The National Health Insurance Service Database of Korea

Diabetes mellitus in breast cancer survivors: metabolic effects of endocrine therapy

Breast cancer is the most common invasive malignancy in the world, with millions of survivors living today. Type 2 diabetes mellitus (T2DM) is also a globally prevalent disease that is a widely studied risk factor for breast cancer. Most breast tumours express the oestrogen receptor and are treated with systemic therapies designed to disrupt oestrogen-dependent signalling. Since the advent of targeted endocrine therapy six decades ago, the mortality from breast cancer has steadily declined; however, during the past decade, an elevated risk of T2DM after breast cancer treatment has been reported, particularly for those who received endocrine therapy. In this Review, we highlight key events in the history of endocrine therapies, beginning with the development of tamoxifen. We also summarize the sequence of reported adverse metabolic effects, which include dyslipidaemia, hepatic steatosis and impaired glucose tolerance. We discuss the limitations of determining a causal role for breast cancer treatments in T2DM development from epidemiological data and describe informative preclinical studies that suggest complex mechanisms through which endocrine therapy might drive T2DM risk and progression. We also reinforce the life-saving benefits of endocrine therapy and highlight the need for better predictive biomarkers of T2DM risk and preventive strategies for the growing population of breast cancer survivors.

Changes in body composition and subsequent cardiovascular disease risk among 5-year breast cancer survivors

Introduction

Cardiovascular disease (CVD) remains a leading cause of death in breast cancer survivors, a growing population. The aim of this study was to determine whether changes in body composition, commonly observed in breast cancer survivors, is associated with subsequent CVD risk.

Methods

This cohort study used the Korean National Health Insurance Service database. The study population included 73,271 5-year breast cancer survivors aged 40 years or above. To assess changes in body composition and its effect on the risk of CVD, validated prediction equations and multivariate Cox proportional hazards regression were used. Changes in metabolic markers (blood pressure, total cholesterol, and fasting serum glucose) according to changes in body composition were calculated by multiple linear regression.

Results

Having persistently high predicted lean body and appendicular skeletal muscle mass percentages (LBMP and ASMP, respectively) among breast cancer survivors was associated with 32% and 40% lower CVD risks than a persistently low predicted LBMP or ASMP, respectively. Conversely, persistently high predicted body fat mass percentage (BFMP) was associated with a higher CVD risk than persistently low predicted BFMP. Additionally, those with a low to high change in predicted BFMP had a higher risk of CVD than those with persistently low predicted BFMP. Changes in body composition were accompanied by changes in metabolic markers.

Discussion

Maintaining high percentages of lean body and appendicular skeletal muscle mass and preventing an increase in fat mass may be beneficial in preventing CVD in breast cancer survivors.

Development of cardiometabolic risk factors following endocrine therapy in women with breast cancer

PURPOSE

Studies comparing the effect of aromatase inhibitor (AI) and tamoxifen use on cardiovascular disease (CVD) risk factors in hormone receptor-positive breast cancer (BC) survivors report conflicting results. We examined associations of endocrine therapy use with incident diabetes, dyslipidemia, and hypertension.

METHODS

The Pathways Heart Study examines cancer treatment exposures with CVD-related outcomes in Kaiser Permanente Northern California members with BC. Electronic health records provided sociodemographic and health characteristics, BC treatment, and CVD risk factor data. Hazard ratios (HR) and 95% confidence intervals (CI) of incident diabetes, dyslipidemia, and hypertension in hormone receptor-positive BC survivors using AIs or tamoxifen compared with survivors not using endocrine therapy were estimated using Cox proportional hazards regression models adjusted for known confounders.

RESULTS

In 8985 BC survivors, mean baseline age and follow-up time was 63.3 and 7.8 years, respectively; 83.6% were postmenopausal. By treatment, 77.0% used AIs, 19.6% used tamoxifen, and 16.0% used neither. Postmenopausal women who used tamoxifen had an increased rate (HR 1.43, 95% CI 1.06-1.92) of developing hypertension relative to those who did not use endocrine therapy. Tamoxifen use was not associated with incident diabetes, dyslipidemia, or hypertension in premenopausal BC survivors. Postmenopausal AI users had higher hazard rates of developing diabetes (HR 1.37, 95% CI 1.05-1.80), dyslipidemia (HR 1.58, 95% CI 1.29-1.92), and hypertension (HR 1.50, 95% CI 1.24-1.82) compared with non-endocrine therapy users.

CONCLUSION

Hormone receptor-positive BC survivors treated with AIs may have higher rates of developing diabetes, dyslipidemia, and hypertension over an average 7.8 years post-diagnosis.

Development of cardiometabolic risk factors following endocrine therapy in women with breast cancer

PURPOSE

Studies comparing the effect of aromatase inhibitor (AI) and tamoxifen use on cardiovascular disease (CVD) risk factors in hormone-receptor positive breast cancer (BC) survivors report conflicting results. We examined associations of endocrine therapy use with incident diabetes, dyslipidemia, and hypertension.

METHODS

The Pathways Heart Study examines cancer treatment exposures with CVD-related outcomes in Kaiser Permanente Northern California members with BC. Electronic health records provided sociodemographic and health characteristics, BC treatment, and CVD risk factor data. Hazard ratios (HR) and 95% confidence intervals (CI) of incident diabetes, dyslipidemia, and hypertension in hormone-receptor positive BC survivors using AIs or tamoxifen compared with survivors not using endocrine therapy were estimated using Cox proportional hazards regression models adjusted for known confounders.

RESULTS

In 8,985 BC survivors, mean baseline age and follow-up time was 63.3 and 7.8 years, respectively; 83.6% were postmenopausal. By treatment, 77.0% used AIs, 19.6% used tamoxifen, and 16.0% used neither. Postmenopausal women who used tamoxifen had an increased rate (HR: 1.43, 95% CI: 1.06-1.92) of developing hypertension relative to those who did not use endocrine therapy. Tamoxifen use was not associated with incident diabetes, dyslipidemia, or hypertension in premenopausal BC survivors. Postmenopausal AI users had higher hazard rates of developing diabetes (HR: 1.37, 95% CI: 1.05-1.80), dyslipidemia (HR: 1.58, 95% CI: 1.29-1.92) and hypertension (HR: 1.50, 95% CI: 1.24-1.82) compared with non-endocrine therapy users.

CONCLUSION

Hormone-receptor positive BC survivors treated with AIs may have higher rates of developing diabetes, dyslipidemia, and hypertension over an average 7.8 years post-diagnosis.