A 69-year-old woman presents to her cardiologist with shortness of breath. She was diagnosed with congestive heart failure (CHF). An echocardiogram showed an ejection fraction (a measure of the pumping function of the heart) of 25%, representing a severe weakness of the heart muscle. Her past medical history is remarkable for left sided breast cancer diagnosed in 2000. She was treated with lumpectomy and chemotherapy. She was felt to be cancer free in 2008. What caused her CHF and her weak heart?
Breast cancer is the most common form of cancer in woman in the United States. Approximately 1 in 8 women will develop breast cancer. Breast cancer does occur in men as well, although it is rare, accounting for only a few cases per year. Breast cancer is treated with surgery, radiation therapy and chemotherapy. Fortunately, cancer treatments are curing more and more breast cancer. Unfortunately, those same treatments can cause heart disease, often years later. Radiation, especially to the left side, can affect all of the layers of the heart. It can affect the outer layer of the heart causing inflammation and chest pain (pericarditis). Radiation can damage the heart muscle and cause it to weaken. Lastly, radiation can cause blockage in the heart arteries. Studies have shown that patients who had radiation for left-sided breast cancer are twice as likely to have heart artery disease as patients with right-sided cancer. Radiation can accelerate blockage starting about 5 years after therapy and the effect may persist for up to 30 years. Chemotherapy agents are very good at inducing cures, but two agents in particular can cause significant heart damage. Adriamycin acts as a toxin to the heart muscle. It causes weakening and a reduction in the ejection fraction, leading to CHF, often 10 to 20 years after the chemotherapy is given. Unfortunately, Adriamycin’s effect is irreversible. Another agent, Herceptin (Trastuzumab) also causes a weak heart muscle and CHF. However, stopping the agent does allow the heart to recover function, so vigilance is needed during its administration.
Breast cancer and heart disease share a number of risk factors including: older age, poor diet, alcohol use, obesity, sedentary lifestyle and smoking. In a two for one deal, exercising, keeping weight down, not smoking and limiting alcohol not only reduces the risk for heart disease, but also lowers the chance of getting breast cancer. This advice is valid for both women and men (remember, men can get breast cancer as well). Two strategies in particular are worth noting for their reduction in both heart disease and breast cancer: exercise and taking a statin for cholesterol. Exercise capacity has shown to be a prognostic factor in breast cancer. Patients with higher levels of physical activity have a lower risk of developing breast cancer and dying from the disease. Patients with better cardiorespiratory reserve, developed from years of exercising, can tolerate the toxic effect of chemotherapy. These patients suffer less cardiac side effects during treatment. In addition, these patients are more likely to stay active during chemotherapy, thus lessening their risk further. Statins may be protective as well. Women who were taking a statin during chemotherapy had a lower risk for CHF. This may be because, beyond lowering cholesterol, statins decrease inflammation and stress in heart cells.
Screening for breast cancer may be a useful tool for screening for heart disease too. The mammogram (an X-ray of the breast) is the standard test for screening for and detecting breast cancer. If a suspicious area is seen on mammography, then a biopsy is done to confirm or rule out cancer. Breast artery calcification may also be seen on mammography. Breast artery calcification, like heart artery calcification, signifies the presence of plaque or blockage in the arterial wall. Heart artery calcification on CT scan is associated with a higher risk for heart attack and heart death and a reason to intensify preventive treatments. Does breast artery calcification have the same prognostic significance? In a study of 5000 women (all over age 60) who did not have breast cancer or heart disease, 26% were found to have breast artery calcification. Those with calcification were twice as likely to have heart disease or stroke. In another two for one deal, it looks like mammography can screen for bother breast cancer and heart disease.
The index case and the three intersections between breast cancer and heart disease teach us the following lessons. Patients who have had breast cancer and who had radiation or certain types of chemotherapy must remain vigilant about heart symptoms and see their doctor if symptoms do occur. With common risk factors, following a healthy lifestyle reaps rewards in numerous ways. Lastly, artery calcification anywhere in the body must be taken seriously and preventive medications must be initiated. Following these measures can help avoid two deadly diseases: breast cancer and cardiovascular disease.
