It seems a cruel irony: the very thing that may have saved your life after a frightening cancer diagnosis is the same thing that can ultimately endanger your heart. I first heard of the known link between cancer treatments and later heart disease when I was a text editor of the palliative care textbook called Medical Care of the Dying.1 I learned about patients with end-stage heart disease caused by their cancer treatments, sometimes decades earlier. . .
Breast cancer survivors, for example, may understandably worry about a recurrence of their cancer some day, but most should be just as concerned about damage to their hearts, according to researcher Dr. Aditya Bardia at Johns Hopkins University. In fact, for almost 80 per cent of the patients she studied, the risk of a serious cardiovascular event caused by cancer treatment was as high as the risk of recurring cancer.2
But make no mistake: as cardiologist Dr. Laxmi Mehta wrote in the first ever American Heart Association scientific statement on Cardiovascular Disease and Breast Cancer in 2018:
“We want people to undergo the best cancer treatments available. But we also want patients and their doctors to be aware that cancer treatment can damage the heart.”
The same scientific statement reported that, particularly in older individuals, the risk of dying from cardiovascular disease “exceeds the risk of dying from breast cancer.”
As survival rates improve with cancer treatment advances, it means that cancer patients live longer – long enough for resulting cardiac damage to make itself known. As a result, a new medical specialty has emerged to address this problem. Cardio-oncology is a partnership of cardiologists and oncologists who combine their knowledge to help protect the hearts of people undergoing cancer treatment.*
There are many possible treatment choices depending on the type of cancer, but the most dangerous to our hearts are:
1. Chemotherapy: Harvard cardiologist Dr. Mandeep Mehra, head of the Center for Advanced Heart Disease at Brigham and Women’s Hospital in Boston, puts it bluntly:
“Almost every chemotherapy drug has some effect on the cardiovascular system, and most are not good.”
2. Radiation therapy can affect the heart whenever any part of the heart is exposed to radiation. This is especially applicable to radiation aimed at the central chest area.
Heart-related problems can happen at any time after the start of therapy, ranging from immediately to months or even years after treatment, and can include:
- Weakening of the heart muscle: (cardiomyopathy, heart failure), generally developing many years after treatment
- Heart rhythm problems (arrhythmia): normal heart function depends on a series of coordinated electrical signals inside the heart that occur at the right time and in the right order. Cancer treatment-induced arrhythmia (CTIA) seems to be more commonly seen following radiation therapy.3
- Heart attack (myocardial infarction), caused by injury to the coronary arteries that supply blood to the heart muscle. Radiation aimed near the heart can cause heart attacks at younger ages than normally expected.
- Heart valve problems: The heart’s four valves help blood move through the heart normally. Radiation therapy can affect heart valves many years after treatment, causing thickening of the valve (regurgitation), or narrowing of the valve (stenosis).
- High blood pressure/blood clots (hypertension); some cancer drugs that suppress new blood vessel formation can cause blood pressure to rise dramatically, and may also increase the risk of blood clots.
- Inflammation of the pericardium, a fluid-filled space surrounding the heart (pericarditis). Radiation therapy can also cause pericardial effusion, or a fluid build-up in the pericardial sac that may need to be removed.
As Dr. Mehra observes:
“The cardiovascular side effects that arise from cancer therapy are frightening.”
Your risk for heart problems due to cancer treatment can also depend on your age, on how healthy your heart is, or on the specific cancer treatment you’ll be receiving. Some treatments may carry a higher risk of heart problems in those who have already been diagnosed with heart disease, and that risk could be even higher if you get a larger dose of a drug or a longer course of radiation therapy.
This makes sense. Just as cancer treatments can damage cancer cells, they can also damage other parts of the body, including the heart, says Dr. Rupal O’Quinn, a cardiologist at the University of Pennsylvania who specializes in cardio-oncology:
“Unfortunately, there are patients who received treatment decades ago when harmful effects were unknown, and are just now experiencing the after effects on their heart.”
Sometimes, heart problems happen as a late effect of treatments for cancer during childhood.
And according to The American College of Cardiology’s CardioSmart site, cardiotoxicity is seen in many types of cancer.
A few examples:
The most common treatments for Hodgkin’s lymphoma are chemotherapy with or without radiation therapy. Radiation therapy for Hodgkin’s lymphoma is often used to treat the mediastinum, an area very close to the heart. Cardiac damage may be increased by the use of certain chemotherapy drugs. Patients can be at increased risk of a heart attack for 25 years following treatment for Hodgkin’s. You may be especially at risk if you received treatment for Hodgkin’s lymphoma as a child.
Cardiac damage typically shows itself about seven years on average after treatment for breast cancer.4 Surgery is a standard part of treatment, but doctors may also treat patients with chemotherapy, radiation therapy, and/or targeted therapies. Women with cancer of the left breast or with cancer in the lymph nodes near the breastbone (sternum) are at higher risk for radiation cardiotoxicity. This effect can be increased by certain chemotherapy drugs. HER2-targeted therapies, for example, has unique side effects that can hurt the heart.
There are many types of lung cancer, but all of them can involve the lymph nodes in the middle of the chest. Lung cancers in the central lungs or in the lymph nodes at the centre of the chest are close to the heart, so radiation therapy to these areas can also hurt the heart.
Because the esophagus passes through the middle of the chest, directly behind the heart, treating this area with radiation therapy can hurt the heart. Surgery is considered standard treatment, with or without radiation therapy and chemotherapy.
If you’ve been diagnosed with cancer, you need answers to several important questions on how your cancer treatments might impact your heart. For example, ask your oncologist these questions:
- Am I receiving any cancer treatment that could affect my heart either now or in the future?
- What are my risk factors for developing cardiac side effects from treatment?
- Are there any ways to decrease the dose of radiation to my heart during treatment?
- What chemotherapies increase my risk of heart damage when combined with radiation?
- What steps can I take to help reduce my risk of developing cardiotoxicity?
- What symptoms might be a sign of cardiotoxicity? When should I call my cancer team right away?
- Do I need to see a cardiologist or cardio-oncologist during or after cancer treatment?*
* Finding a cardio-oncologist: good luck with that!
– Canada: The national Canadian Cardiac Oncology Network offers information to patients on cardiac tests, treatments, conditions, research opportunities – and a “Find a Clinic” feature that lists just four such specialist clinics in the whole country: Ottawa (Ottawa Hospital), Toronto (Scarborough Hospital), Edmonton (Mazankowski Alberta Heart Institute) and Vancouver (Vancouver General Hospital/Gordon and Leslie Diamond Health Care Centre)
– U.S.A: CardioSmart suggests that you “search the Department of Cardiology website of the medical school nearest you, or ask your cancer doctors if they know a cardio-oncologist in the area.” The International Cardio-Oncology Society also provides contact information for member chapters in over a dozen countries. But their “Find a Clinic” page says “Coming Soon”.
-Australia: The Australian Cardio-Oncology Registry (ACOR) lists a national partnership of 11 hospitals/research institutions focused on children and young adult cancer patients at risk for heart disease.
-U.K: The British Cardio-Oncology Society is a professional group associated with the British Cardiovascular Society, mostly geared to health care professionals, with links to research and practice guidelines.
1. Medical Care of the Dying, 4th Edition, G. Michael Downing, Wendy Wainwright, Victoria Hospice Society, 2006.
2. Bardia A, et al. “Comparison of breast cancer recurrence risk and cardiovascular disease risk among postmenopausal breast cancer survivors”. ASCO Breast, 2009; Abstract 133.
3. Buza, V et al. “Cancer Treatment-Induced Arrhythmias”. Circulation: Arrhythmia and Electrophysiology. 2017;10
4. Bradshaw PT et al. “Cardiovascular disease mortality among breast cancer survivors.” Epidemiology. 2016; 27:6–13.