Effects on the heart

Certain chemotherapy drugs and the targeted therapy drug trastuzumab (Herceptin®) can increase the risk of heart problems in the future. An early menopause can change the way the heart works too.

Women with conditions such as high blood pressure are more at risk and need checks during treatment. Some women will be monitored before, during and after treatment to keep a check on the heart.

Radiotherapy when it’s given to the left breast has a very low risk of causing heart problems. Newer techniques mean that the heart receives very little radiation.

Let your doctor know if you have any of the following symptoms:

  • a fast, or irregular heart beat
  • pain or discomfort in your chest
  • getting breathless easily
  • feeling weak or dizzy
  • tiring very quickly
  • swelling in the feet and lower legs.

Because they may appear a long time after treatment, it’s important to remind your doctor of the treatments you had. You may reduce your risk of heart problems by keeping active, eating healthily, not smoking and sticking to sensible drinking guidelines.

How breast cancer treatment can affect the heart

Some treatments for breast cancer may increase the risk of getting heart problems, usually many years later. You will have been monitored closely during and after treatment to reduce the risk of this happening. Most women won’t ever experience any effects on the heart. But it may help to understand more about them and how you can help look after your heart.

The most important risk factor for developing future heart problems is pre-existing heart disease, including high blood pressure. Women at risk are carefully monitored before and during their treatment to find out if their treatment needs to be changed. Many women who have these drugs won’t ever experience heart problems.


The standard chemotherapy for early breast cancer usually includes drugs known as anthracyclines, for example epirubicin or doxorubicin. This is an effective treatment for breast cancer as evidence shows that these drugs are good at reducing the risk of it coming back.

In a small number of women, treatment with anthracyclines may result in slight damage to the heart muscle. Because these changes are slight, they usually don’t cause any immediately noticeable effects. But they may lead to an increased risk of heart problems developing much later in life.


After radiotherapy to the chest, there is a very small risk of damage to the heart muscle or the major blood vessels around the heart. This is only a potential problem if you’ve had cancer in your left breast, as the heart is on the left side of the chest. Radiotherapy is now very carefully planned, so that the heart is either outside the radiation area completely, or only a small part of the heart will receive any radiation. As a result, the risk of developing any heart problems is now very low.

An early menopause

Having an early menopause due to your treatment may also increase the risk of heart problems. This is because oestrogen and progesterone help protect the heart. Hormonal drugs, called aromatase inhibitors, may also increase the risk of high cholesterol, which can lead to heart problems.

Targeted therapy

Trastuzumab (Herceptin) can cause changes in the way the heart functions, particularly in women who already have heart disease. Because of this, it’s not given to women with some types of heart condition. Tests are done before treatment and women are checked regularly throughout and after treatment.

If heart problems occur during treatment with trastuzumab, they are usually temporary, improve with medication and get better after treatment finishes.

Possible symptoms of heart problems

There are some symptoms that can be linked with heart problems. But they can be caused by lots of other things. As problems can occur many years after treatment, you may need to remind your doctor about the cancer treatments you’ve had.

Let your doctor know if you have any of these symptoms:

  • feeling your heart beating fast, hard or irregularly
  • pain or discomfort in your chest
  • getting breathless, for example when climbing stairs
  • feeling weak or dizzy
  • getting tired very easily
  • swollen feet and lower legs.

If you have heart problems, your doctor will refer you to a heart specialist (cardiologist).

What you can do

Making small changes to your lifestyle may help reduce your risk of developing heart problems. If you already have problems, small changes can help to reduce your risk of further problems.

The British Heart Foundation has lots of information and advice on keeping your heart healthy.

Keep physically active

This can help your heart health and has other benefits too. It helps you to keep to a healthy weight and reduces your risk of bone thinning (osteoporosis). It can reduce stress and improve fatigue. You’ll also look and feel better.

There’s also some evidence that regular exercise may help to reduce the risk of breast cancer coming back as well as reducing the risk of getting some other cancers.

Eat healthily

Eating healthily helps to protect your heart and keep your weight healthy. 

Try to eat:

  • at least five portions of fresh fruit and vegetables a day
  • more chicken and fish (especially oily fish)
  • more high fibre foods
  • less saturated fat (such as pastries, cakes, cheese)
  • less red and processed meat
  • less salt.

After breast cancer, some women want to know if they should avoid dairy foods or if there’s a particular diet they should follow. Studies that have looked for a connection between diets that are high in dairy products and breast cancer haven’t shown a clear link. So, cancer experts don’t recommend following a dairy-free diet. Dairy products are also a good source of calcium, which is important for bone health.

There’s also a lot of publicity about alternative diets for treating cancer, but there’s no evidence that they increase a person’s chance of survival. Some of these diets may lack important nutrients or be unbalanced in other ways and may even be harmful.

Doctors and specialist nurses recommend a healthy, well-balanced diet and one that you enjoy.

Cut down on alcohol

Too much alcohol can cause heart problems and it’s also high in calories. Stick to sensible drinking. Current guidelines recommend that both women and men drink no more than 14 units of alcohol per week.

Give up smoking

If you smoke, stopping is the healthiest decision you can make. It’s one of the major risk factors for heart disease. Stopping smoking also reduces your risk of developing lung disease, bone thinning (osteoporosis) and smoking-related cancers. You’ll also feel and look better.

Giving up smoking isn’t easy. You can increase your chance of success by preparing for possible problems in advance. You can also make sure that you have support in place to help you overcome them. Using a treatment to reduce cravings can double your chances of success. There’s a range of treatments available on prescription. Your GP can tell you about them and help you choose the one that’s best for you.