Cancer and Heart Disease

February is Heart Month and let's talk about the impact of cancer on heart disease!

It is well established that some cancer treatments can affect the heart with either short-term and/or long-term risks. Some of the heart conditions that are associated with cancer treatment include congestive heart failure, coronary artery disease, high blood pressure, high cholesterol, and arrhythmias (irregular or fast/slow heartbeats). There are a number of cancer drugs that can increase the risk of heart disease including anthracycline chemotherapy (this includes doxorubicin, which many refer to as the “red devil.”), anti-HER2 based treatments, immunotherapy drugs, some targeted therapies such as tyrosine kinase inhibitors, among others. Left sided radiation for breast cancer or treatment for Hodgkin lymphoma as a child can also increase risk. People with prior heart disease or cardiac risk factors (including high blood pressure, diabetes, high cholesterol and smoking history) may be at higher risk of developing heart disease from cancer treatment. Cardio-oncology is a cardiology subspecialty that focuses on treating and preventing cancer-related heart disease.

Photo by Mara Ket on Unsplash

A question I get often is “how do I know if I need to see a cardiologist (or a cardio-oncologist)?” If your cancer treatment increased your risk for heart disease, it is worth considering (and especially if you have underlying cardiac risk factors or already diagnosed heart disease). People who are about to start cancer treatment and have a high baseline cardiovascular risk are often referred as well. Both of these are preventive approaches to try to reduce the risk of heart disease in the future. Of course, if you develop any cardiac problems during treatment or after treatment (that’s related to your treatment), you will be referred to a cardiologist as well. **Not all cancer centers or hospitals have dedicated cardio-oncology programs but it is a good question to ask your medical team. If you are not sure whether your cancer treatment puts you at higher risk for heart disease, ask your oncologist and they can help you decide whether seeing a cardiologist is right for you.

Do calcium supplements increase the risk of heart disease?

We know that calcium is important for bone health. The Bone Health and Osteoporosis Foundation recommends that women under age 50 need 1,000 milligrams of calcium daily and women age 50 and older (or any woman who is not menstruating) need 1,200 milligrams of calcium daily. This recommendation is a combination of diet and supplements. Some studies, however, have shown that calcium supplementation may increase cardiovascular risk. There are some limitations and caveats to some of these studies and so this topic remains controversial. We do know that if there is a risk, it is going to be with higher amounts of calcium supplementation (>1,000-2,000 milligrams daily). This does not apply to dietary calcium risk. I recommend trying to focus on calcium intake through diet and supplement what you are not consuming. Calcium amounts are reported on nutrition labels so you can get a sense of how much calcium you consume on a daily basis.

What is the risk of cardiovascular disease from anthracyclines?

Anthracyclines (doxorubicin, daunorubicin, idarubucin, epirubin) are chemotherapy drugs that can cause cardiotoxicity. These drugs are used to treat many different cancers including breast cancer, leukemia and lymphoma. Anthracyclines can affect the left ventricular function of the heart (the left ventricle is what supplies oxygenated blood to the body). This is measured as the ejection fraction. A decrease in left ventricular function can lead to heart failure. Some people may have a mild drop in the ejection fraction but will not have symptoms from it and others will have heart failure symptoms (such as shortness of breath, fatigue and swelling in the legs).

There can be acute cardiotoxicity which develops during or shortly after anthracycline treatment and is generally reversible when the drug is discontinued. This is rare and occurs in <1% of cases. Most commonly, we see early onset cardiotoxicity which appears within the first year after treatment. The risk of late onset cardiotoxicity (more than 1 year after exposure) is not as common but can happen. Older patients and those with underlying cardiac risk factors such as diabetes or high blood pressure are at higher risk of developing cardiotoxicity.

Cardiotoxicity is dose dependent and there is a cumulative lifetime dose (there are unique situations where you may need more anthracyclines and than that requires close monitoring and cardioprotective medications). The incidence of cardiotoxicity varies depending on which study you look at but several large studies have shown an incidence of a decline in ejection fraction of about 6-7% (this does not necessarily mean someone is symptomatic). Everyone should have an echocardiogram before starting anthracycline therapy and ASCO recommends a 6 to 12 month follow up echocardiogram after completion of therapy in patients at high risk of cardiac toxicity. We don’t have any other routine recommendations beyond that so it is important to talk to your doctor about whether you would benefit from seeing a cardiologist.

What is the risk of cardiovascular disease with endocrine therapy?

Tamoxifen is associated with an increased rate of venous thromboembolic events (deep venous thrombosis and pulmonary embolism- blood clots in the extremities (usually in legs) and in the lungs). The risk is about 2-3 times higher in people taking tamoxifen compared with those not taking tamoxifen. A careful assessment of blood clot risk before starting tamoxifen (including family history of blood clots) is important. We typically avoid tamoxifen in people with prior blood clots. Some, but not all, data also suggest a higher risk of stroke. On a positive side, tamoxifen may improve cardiovascular events but this data is conflicting as well (some studies do not show a benefit).

What about aromatase inhibitors? AIs can increase blood pressure and cholesterol and both should be monitored regularly. Some studies have shown that AIs are associated with cardiovascular disease but this data is not consistent and some of the risk may come from the elevation of blood pressure and cholesterol. Given the potential protective benefit of tamoxifen, the studies have shown that aromatase inhibitors do have a higher risk of cardiovascular disease when compared to tamoxifen but in general, do not have a higher risk when compared to placebo.

Ultimately, cardiovascular risk and blood clot risk are some of the factors that we consider when making a decision between tamoxifen and aromatase inhibitors.

These are some of the most common questions I receive about cancer and heart disease! I hope you found this helpful and please share with someone who may find this helpful as well. Let me know if you have other heart disease and cancer questions I can address!