Cancer treatments and the heart

For people experiencing cancer, treatments including chemotherapy, immunotherapy and radiotherapy can be lifesaving. It’s important to know that some cancer treatments have side effects that can affect the health of your heart. This is called cancer therapy-related cardiotoxicity, or cardiotoxicity for short.

You may also hear the word cardio-oncology. This is the name for the field of medicine which studies, prevents and treats cardiotoxicity.

While it is important to be aware of these potential heart-related side effects, not all cancer treatments damage the heart. Your healthcare team will monitor you for any signs of cardiotoxicity and adjust your treatments as needed to manage these risks effectively.

What causes cardiotoxicity?

Cardiotoxicity is damage to the structure or function of the heart, caused by certain cancer treatments.

Cardiotoxicity may happen during cancer treatment or might not develop until after the treatment has finished. In some people who are already living with cardiovascular disease (CVD) before cancer treatment, it may worsen their current condition.

The risk of developing cardiotoxicity can change depending on the type of cancer treatment you are having, any pre-existing conditions you have, along with other risk factors.¹ Some shared risk factors between CVD and cardiotoxicity are:^1,2

• pre-existing CVD
• high blood pressure, high cholesterol or diabetes
• type of cancer – a higher risk of cardiotoxicity has been seen with lung, prostate, rectal and colon cancer
• previous exposure to cardiotoxic treatments – for example previous treatment with chemotherapy
• age, sex and genetics
• lifestyle risk factors – particularly smoking, alcohol consumption and low physical activity levels.

Cancer treatments and your heart

Along with surgery, chemotherapy, immunotherapy and radiotherapy are the most used treatments for cancer in Australia.

Chemotherapy

Chemotherapy uses medicines to kill cancer cells. These medicines target cells that are multiplying. This means that as well as cancer cells that are multiplying abnormally, they can also kill healthy cells that are supposed to be multiplying – sometimes causing side effects. There are many different types of medicines used for chemotherapy, and the type, dose and number of treatments depends on what type of cancer is being treated.

Some of the chemotherapy agents that might cause cardiotoxicity are:

• anthracyclines attach to the DNA inside cells, which blocks the proteins that copy a cell’s DNA from attaching where they need to. This means that the cells can’t divide and tissues can’t grow. Medicines in this group include epirubicin and doxorubicin. Anthracyclines have been linked to abnormal heart rhythms (arrhythmias), inflammation of the heart tissue, heart failure and heart attacks. Anthracycline chemotherapy may lead to cardiotoxicity which can happen within a year of treatment, or as long as 20 years later.⁴ People receiving anthracyclines are always carefully monitored during and after their treatment.

• alkylating agents damage the DNA in cells so that they can’t divide. Medicines in this group include cyclophosphamide. Alkylating agents have been linked to inflammation of the heart tissue and heart failure.^5,6

• mitotic inhibitors stop cells from building the framework they need to use when they divide. Medicines in this group include 5-fluorouracil and capecitabine. Mitotic inhibitors have been linked to reduced blood flow to the heart.⁶

Immunotherapy

Immunotherapy uses your own immune system to kill cancer cells. Part of your immune system’s job is to find and attack cells that are behaving abnormally. But cancer cells often have ways to hide. Immunotherapy helps your immune system find these cancers cells. Like chemotherapy, there are different types of immunotherapy:

• monoclonal antibodies hold on to proteins on the surface of cells, stopping the messages that tell the cell to divide. Medicines in this group include trastuzumab and bevacizumab. Monoclonal antibodies have been linked to a reduction in how much blood your heart pumps out (called reduced left ventricular ejection fraction (LVEF)), heart failure and high blood pressure (hypertension).^5,6
• immune checkpoint inhibitors hold on to proteins on the surface of cells which helps your immune system recognise them as a target. Immune checkpoint inhibitors have been linked to inflammation of the heart, atherosclerosis and cardiomyopathy.⁷

Radiotherapy

Radiotherapy uses radiation to kill cancer cells. Usually this is focused beams of high-energy x-ray, but sometimes it can be electron beams, proton beams or gamma rays. Radiotherapy may cause cardiotoxicity by causing inflammation and scar tissue to build up in your heart.^5,6

What heart conditions are associated with cardiotoxicity?

Some of the most commonly seen are:

• arrhythmias – arrhythmia is a fault in the heart’s electrical system, which affects your heart’s pumping rhythm. There are many different types of arrhythmia which can start in either the atria or ventricles of your heart and can cause a fast heartbeat (tachycardia), slow heartbeat (bradycardia) or irregular heartbeat.
• hypertension – hypertension is when your blood pressure is persistently higher than normal. High blood pressure is one of the main risk factors for heart disease, especially heart attacks and strokes.
• coronary heart disease – coronary heart disease (sometimes called coronary artery disease) occurs when a coronary artery clogs and narrows because of a buildup of plaque.
• heart failure – heart failure is a condition where your heart isn’t pumping blood to the rest of your body as well as it should. If your heart is damaged or not pumping properly, it can become enlarged, weak or stiff.
• myocarditis and pericarditis – myocarditis and pericarditis are both inflammation of the heart. Myocarditis is inflammation of the heart muscle, while pericarditis is inflammation of the sack-like tissue that surrounds the heart.
• cardiomyopathy – cardiomyopathy is a term that covers a number of conditions that involve changes to your heart muscle which make it harder for the heart to pump blood to the rest of your body.
• pericardial effusion – pericardial effusion is a build-up of fluid around the heart.⁸ This can affect the way that the heart functions.

How is cardiotoxicity diagnosed?

Diagnosing cardiotoxicity uses many of the same tests that are used for diagnosing CVD generally. These may include:¹

• electrocardiogram (ECG) – an ECG reads your heart’s electrical impulses. Small sticky dots and wire leads are put on your chest, arms and legs. The leads are attached to an ECG machine which records the electrical impulses and can detect abnormal heart rhythms.
• blood tests – cardiac troponin (cTn) and natriuretic peptide (NP) are proteins that the cells of your heart release if they are damaged. Measuring the amount of them in your blood can indicate if cardiotoxicity has occurred from your cancer treatment. You may also have measurements of cholesterol and tests for diabetes.
• echocardiogram – gives a picture of your heart using ultrasound. It can show if there are any problems with your heart’s valves and chambers and see how strongly your heart pumps blood.
• magnetic resonance imaging (MRI) – uses magnets and radiowaves to make live, three-dimensional images of your heart. It can show changes in the structure or function of the heart and how blood flows through it. This can show your healthcare team if your heart is pumping out less blood (reduced left ventricular ejection fraction (LVEF)).

In many cases these tests will be done before beginning your cancer treatment so that your healthcare team can assess your risk of developing cardiotoxicity and manage your cancer treatment accordingly.

What are the treatments for cardiotoxicity?

The treatment for cardiotoxicity will depend on what caused it and what conditions/symptoms you are experiencing. Treatments may include:¹

• changing your cancer treatment – this may mean taking a different chemotherapy medicine or stopping one of them for a short time. Sometimes more than one chemotherapy medicine is taken, so it could also mean that a different combination of medicines are prescribed to you.
• taking medicines – your healthcare team may prescribe medicines that are used to treat heart conditions. These could include beta blockers, angiotensin-converting enzyme (ACE) inhibitors or angiotension receptor blockers (ARBs) that manage your blood pressure and/or heart failure; diuretics to help with fluid retention; more advanced treatments for severe heart failure; drugs to control abnormal heart rhythms; or anticoagulants that stop blood clots from forming.
• lifestyle modification – stopping smoking and reducing alcohol intake have a beneficial effect on your heart. Being physically active can improve the symptoms and side effects of cardiotoxicity and has been shown to be particularly helpful for people recovering after cancer treatment.

It is important that these treatment decisions are made by an experienced healthcare team. Don’t start, stop or change any medicines you are taking without speaking to your healthcare provider. If you are undergoing or have recently had treatment for cancer, speak to your healthcare provider before changing your diet or beginning any new physical activities.

Living well after treatment

Because there is a range of different cancer treatments, and every person’s body can react to them in a different way, it is important to speak to your healthcare professional to develop a personalised plan that works for you.

You can help to keep you heart healthy by:

Further information and support

What research is the Heart Foundation funding?

The Heart Foundation is funding research to enhance our understanding, diagnosis and management of cardiotoxicity and cardio-oncology.

Some projects that we have funded include: