Effects of Breast Cancer Treatments on Cardiovascular Disease Risk Factors

The survival rate of women with breast cancer has been steadily increasing each year since 2007. The 5-year survival rate for women with nonmetastatic invasive breast cancer is currently 90%.¹ As survival rates have increased, studies have demonstrated that rates of cardiovascular disease in the same population have been increasing as well. This is an important observation, as cardiovascular disease is already a common condition in women, and is currently the leading cause of death in women in the United States.² 

The recently published Pathways Heart Study sought to determine the risk of cardiovascular disease and death in women who underwent treatment for breast cancer compared with women who did not have breast cancer. The study looked at multiple treatments for breast cancer, including chemotherapy, radiation, and endocrine therapy. The chemotherapy groups were further broken down into 4 subset groups: anthracyclines without trastuzumab, anthracyclines with trastuzumab, trastuzumab without anthracyclines, and chemotherapy that did not include either trastuzumab or anthracyclines.³ 

For those who underwent radiation therapy, both sides of the body were recorded, with special focus on those who received radiation to the left side. Endocrine therapy was grouped into treatment with tamoxifen or aromatase inhibitors.³ 

Cardiovascular Risks With Breast Cancer Treatments

Trastuzumab The cardiac risk factors associated with the HER2-directed therapy trastuzumab are well established. Trastuzumab has the potential to cause left ventricular (LV) dysfunction, hypertension, and arrhythmias, and requires routine cardiac evaluation during therapy. If LV dysfunction is documented, trastuzumab should be held and rechallenged based on improvement of LV function.⁴ 

Anthracyclines Cardiotoxicity is a known risk with use of anthracyclines, and due to cumulative risk, lifetime dosages have been established. The exact cardiovascular risk is dependent upon the age of the patient as well as the cumulative dose of anthracyclines they received. Cardiotoxicity from anthracyclines primarily consists of cardiomyopathy resulting in heart failure. 

Radiation Radiotherapy for breast cancer has the potential to cause long-term cardiac toxicities, including coronary artery disease, myocardial infarction, heart failure, arrhythmias, and valvular disease.⁵ 

Endocrine therapy Studies have demonstrated that the cardiovascular risks associated with endocrine therapy are most likely to occur with use of aromatase inhibitors over tamoxifen. Aromatase inhibitors have the potential of causing coronary artery disease, myocardial infarction, arrhythmias, heart failure, pericarditis, and valve disease. Tamoxifen has actually shown to be cardioprotective but does carry an increased risk of venous thromboembolism (VTE).⁶