Cardio-Oncology: Radiation and Heart Disease

Being told you have cancer is a life-changing experience for most patients and leads to many new concerns such as:

What is my prognosis ?

What are my treatment options?

How will my life be different with cancer?

How am I going to share this news with my loved ones?

Typically, concerns about the potential impact of cancer treatment on the heart are not among the first that come to mind. However, some patients with cancer may receive radiation therapy to the chest area, and these patients should be aware of the side effects that radiation therapy may cause to the heart. These potential adverse effects are known as radiation cardiotoxicity.

Radiation cardiotoxicity may affect the heart in various ways and at any time. Some conditions develop during or soon after treatment. Others become apparent years, or even decades, after treatment. The specific adverse effects depend on which area of the heart is affected, such as injury to the heart muscle, the heart lining, or blood vessels. Examples of the conditions that may develop include cardiomyopathy, coronary artery disease, and heart rhythm problems.

Radiation treatment can be delivered using several methods. The specifics of your treatment will influence your risk of developing radiation cardiotoxicity. In addition, many other factors may increase or decrease your risk, including age, additional cancer treatments, and other heart risk factors. Your oncologist (cancer doctor), radiation oncologist (radiation doctor), or cardiologist (heart doctor) will help you understand your unique risk from radiation.

Use this condition center to learn more about radiation cardiotoxicity, radiation techniques, and tips for healthy living after cancer treatment.

Cancers Linked to Heart Problems

If you have cancer, your physician may recommend a treatment that involves radiation therapy to the chest area. You should be aware of the side effects that radiation therapy may cause to the heart. These potential adverse effects are known as radiation cardiotoxicity.

In this section, you will learn about cancers that have a higher risk of causing radiation injury to the heart.

Hodgkin’s Lymphoma

Overview: Hodgkin’s lymphoma is a cancer of the lymphatic system that arises from a type of white blood cells called lymphocytes. It frequently involves the lymph nodes in the center of the chest. This area, called the mediastinum, is next to the heart. It typically affects young adults (ages 20-35) or older adults (ages 55 and up).

Causes: The exact cause of this cancer is unclear. Some scientists believe that a virus, called the Epstein-Barr virus, causes changes in lymphocytes that lead to Hodgkin’s lymphoma.

Symptoms: Most patients have a painless mass in the neck, underarm, or groin. If the mediastinum is involved, patients may notice shortness of breath or chest pain. Some patients may also have fevers, excessive sweating (especially at night), intense itching, severe fatigue, and weight loss.

Treatment: The most common treatments for Hodgkin’s lymphoma are chemotherapy and radiation therapy.

Risk of Radiation Cardiotoxicity: Radiation therapy for Hodgkin’s lymphoma is often used to treat the mediastinum. This area is very close to the heart, and therefore the heart can receive some radiation during treatment. This risk may be increased by the use of certain chemotherapy drugs, such as anthracyclines (e.g. doxorubicin).

Breast Cancer

Overview: Breast cancer is the most common type of cancer in women. It can sometimes spread to involve the lymph nodes around the breast. These lymph nodes are found in the underarm area and next to the breastbone (sternum).

Causes: Breast cancer most commonly affects older women, although younger women can also develop breast cancer. A woman’s risk for breast cancer may be influenced by hormonal factors such as high estrogen exposure and by reproductive factors including age at first pregnancy and age at menopause. Being overweight also increases the risk of breast cancer in older women. In addition, genetic mutations may be inherited that greatly increase the risk of developing breast cancer in some families, such as mutations in the BRCA1 or BRCA2 genes.

Symptoms: Common symptoms of breast cancer may include a mass in the breast or underarm area. However, with mammograms, many breast cancers are now found before they cause symptoms.

Treatment: Surgery is a standard part of treatment for most women with breast cancer. Doctors may also treat patients with chemotherapy, radiation therapy, and/or targeted therapies

Risk of Radiation Cardiotoxicity: Women with cancer of the left breast or with cancer in the lymph nodes near the breastbone (sternum) may be at a higher risk for radiation cardiotoxicity. Radiation therapy to these areas can affect the heart. The risk of radiation cardiotoxicity may be increased by the use of certain chemotherapy drugs, such as doxorubicin.

Lung Cancer

Overview: There are many types of lung cancer, but all of them can involve the lymph nodes in the middle of the chest. This disease remains the No. 1 cause of cancer death in the United States and across the world. Lung cancer is a serious disease, but in its early stages some patients can be cured.

Causes: Smoking is the single biggest cause of lung cancer. Less common causes include exposure to radon gas and asbestos.

Symptoms: Cough, chest pain, and shortness of breath are the most common symptoms of lung cancer.

Treatment: Like many cancers, treatment of lung cancer is different depending on which parts of the body are involved. In some cases, doctors perform surgery, which may be followed by chemotherapy or radiation therapy, or both. In other cases, surgery is not performed and doctors recommend radiation therapy, or a combination of radiation therapy and chemotherapy. In many cases, doctors treat with chemotherapy or targeted radiation therapy alone.

Risk of Radiation Cardiotoxicity: Radiation therapy is frequently used in lung cancer. Lung cancers in the central lungs or in the lymph nodes at the center of the chest are close to the heart. Therefore, radiation therapy to these areas can also affect the heart.

Esophageal Cancer

Overview: The esophagus is a muscular tube that carries food from the back of the mouth, through the middle of the chest, and to the stomach. Two types of cancer can affect the esophagus: squamous cell carcinoma and adenocarcinoma.

Causes: Smoking and alcohol use are the main causes of squamous cell carcinoma of the esophagus. In contrast, adenocarcinoma of the esophagus is caused mainly by stomach acid.
Symptoms: Both types of esophageal cancer cause similar symptoms. Patients find it difficult or painful to swallow, which can lead to weight loss.

Treatment: Most patients undergo combinations of treatments for esophageal cancer. Surgery is considered standard treatment. However, patients with aggressive disease may receive radiation therapy and chemotherapy in addition to surgery. If patients cannot have surgery, they may receive radiation therapy and chemotherapy together.

Risk of Radiation Cardiotoxicity: Because the esophagus passes through the middle of the chest, directly behind the heart, treating this area with radiation therapy can affect the heart.

Heart Conditions Caused by Radiation

Radiation therapy can affect any part of the heart. Different forms of radiation cardiotoxicity result, depending on which area was damaged. This section covers the most common types of radiation cardiotoxicity.

Pericarditis and Pericardial Effusion

Radiation therapy to the heart can cause irritation and inflammation of the pericardium, a fluid-filled space surrounding the heart. Such inflammation, known as pericarditis, can occur at any time after the start of radiation, from immediately to months or years after treatment. Symptoms of pericarditis include shortness of breath and chest pain that may be eased by leaning forward. If the inflammation is significant, it can also spread to the heart muscle, and is termed “myopericarditis.”

Radiation therapy can cause pericardial effusion, or the development of a fluid collection in the pericardial sac. Such fluid buildup can cause shortness of breath, chest pressure and lightheadedness. It may need to be removed.

Cardiomyopathy and Heart Failure

Radiation therapy can injure and scar the muscle cells of the heart. This scarring can cause the heart muscle to become weak or stiff. These conditions are known as cardiomyopathies. Weakening or stiffening of the heart muscle can make it difficult for the heart to pump enough blood to meet the body’s needs, a condition called heart failure. One of the main symptoms is fluid buildup in the body, especially the lungs and legs. Cardiomyopathy and heart failure from radiation therapy generally develop many years after treatment.

Coronary Artery Disease, Atherosclerosis and Heart Attack

The coronary arteries supply blood to the heart. Any disruption in this blood supply can interfere with the heart’s pumping function. Coronary arteries can become blocked or clogged with atherosclerosis or plaque. A significant blockage or sudden blockage in the coronary arteries can be very serious. This can lead to severe damage or death of heart tissue and is known as a heart attack (also called myocardial infarction). Common symptoms of a heart attack include shortness of breath, and chest pain or pressure that can come and go or be constant. These symptoms can be observed during or made worse by exertion. Less common symptoms are sweating, nausea, weakness, lightheadedness, and fatigue. If you think you are having a heart attack, dial 911 at once.

Radiation therapy in the area of the heart can injure the coronary arteries. This injury can speed up atherosclerosis and increase the risk of a heart attack. Coronary artery disease caused by radiation therapy generally develops many years after treatment. However, with radiation, the development of heart disease occurs earlier than normal. As a result, patients who receive radiation therapy in the area of the heart can develop coronary artery disease at younger ages than normally expected. So it is important for these individuals to be screened for heart disease. Your doctor may recommend stress testing to assess your heart.

Heart Valve Disease

The heart contains four valves that help blood move through the heart normally. They open to let blood flow forward and close to prevent blood from flowing backward. Radiation therapy can cause thickening, fibrosis, and calcium buildup of the valves. This prevents the valves from fully closing, leading to backward flow (regurgitation). This can also cause thickening and narrowing of the valves, which prevents opening and limits forward flow (stenosis). Both regurgitation and stenosis can occur many years after radiation therapy. Common signs are shortness of breath (worse with exertion), swelling in the ankles, fatigue, weakness, chest pressure, and lightheadedness.

Heart Rhythm Problems (Arrhythmias)

Normal heart function relies on a series of coordinated electrical events inside the heart that occur at the right time and in the right order. This rhythm repeats tens to hundreds of thousands of times throughout the day and is controlled by the heart’s electrical wiring system (conduction system). Radiation therapy can damage the conduction system and disturb the rhythm of the heart.

Any disturbance in the heart’s rhythm is called an arrhythmia. With some arrhythmias, heart rhythm is abnormally fast, and with others, the rhythm is too slow. Arrhythmias caused by radiation therapy are not common. However, when they do develop, they can be slow arrhythmias and occur months to years after treatment. Early on, they may be fast rhythms (for example atrial fibrillation, supraventricular tachycardia).

Radiation Risks

Many factors influence the risk of radiation causing heart problems or making them worse. Your doctor will consider your individual case and work with you to select the most effective treatment for limiting your risk of developing heart problems. Here we will explore many of these considerations in radiation treatment.

Total Radiation Dose

Depending on the type of cancer you have, your doctor will use a specific total dose or amount of radiation to treat your cancer. Over time, many studies have been conducted to identify the most effective, yet safest dose, to cure or control your cancer. In some cases, data received from such studies have resulted in a decreased radiation dose compared to what has been considered standard care in the past.

For example, studies of Hodgkin’s lymphoma have led to using patient characteristics to determine the lowest dose of radiation that will control lymphoma. The dose of radiation is measured in units of Gray (Gy). As an example, in patients with favorable Hodgkin’s lymphoma, some patients may receive a dose as low as 20 Gy as compared to higher risk patients, who may require a radiation dose of 30-45 Gy to treat their lymphomas.

Radiation Fields

Radiation oncologists attempt to limit the area of tissue treated with radiation (called the radiation field) without decreasing needed treatment of the cancer. The risk of developing heart toxicities after radiation is associated with the amount and areas of the heart within the radiation field. Even if the heart is not targeted in your treatment, there may be some overlap of radiation to the heart depending on where your cancer is located.

Types of radiation fields:

Extended field radiation therapy (EFRT): With Hodgkin’s lymphoma as an example, in the past, patients were treated with larger radiation fields called “extended field radiation therapy,” which included both the cancerous lymph nodes as well as healthy lymph nodes in the region. Typically, this included lymph nodes in an area near the heart called the mediastinum.

Involved field radiation therapy (IFRT): However, with improvements in chemotherapy and radiation, studies have shown that the field can be smaller and the radiation aimed only to the region of cancerous lymph nodes. This is called “involved field radiation therapy.”

Involved site radiation therapy (ISRT): Even more recently, the concept of “involved site radiation therapy,” has been used. ISRT treats the cancerous regions and typically treats a smaller field than what would be treated with IFRT.

Your radiation oncologist will help determine what area needs to be treated by taking into consideration many factors, including a physical exam, diagnostic imaging, and a thorough medical history. The oncologist will also confirm whether chemotherapy and/or certain targeted agents being used in your treatment and, if so, your response to these therapies. Although your doctor will attempt to reduce the radiation dose to your heart, the main concern is to control the cancer.

Another disease in which radiation fields may increase the dose to your heart is breast cancer, specifically when it is on the left side. Because the heart lies just behind the left breast, there is a risk of higher radiation dose to the heart when treating this area. Radiation oncologists work to treat patients effectively for their cancers but limit the dose to the heart.

Some patients need to receive radiation to lymph nodes by the breast bone (sternum). However, there are ways that a radiation oncologist can attempt to decrease the dose to this area. Again, although it is important to limit the dose of radiation the heart receives, your doctor will not want to compromise the chance of curing your cancer.

Age

Studies have shown that receiving radiation at a younger age is associated with a greater risk of developing heart disease later in life. As treatment of cancer improves, we are, thankfully, seeing more patients survive their cancer and live many years after treatment. Since radiation effects on the heart can occur years after cancer treatment has ended, it is especially important that young cancer patients follow up regularly with doctors throughout their lives.

Radiation Techniques

Another way to limit the dose of radiation to the heart is through how the radiation is delivered.

3D-conformal radiation (3DCRT) is a delivery method that shapes the radiation dose around normal or healthy tissues in your body. This is done by taking a CT of your body in the position in which you will receive treatment. With this CT scan, the radiation oncologist and dosimetrist (a person trained in developing radiation plans using computer software systems) work to design a plan that avoids healthy tissue and targets the cancerous tissue. The treatment is delivered from a few angles. They are all focused directly at the cancer, and thus the highest dose of radiation combines from these different angles to increase the dose to the cancer and limit the dose to healthy tissue.

Intensity-modulated radiotherapy (IMRT) is similar to 3DCRT in that it is used to deliver the highest dose of radiation to the tumor and decrease the radiation to surrounding healthy tissue. This is done by using small pieces of metal that move in and out to shape the radiation around the tumor itself. However, it is important to know that this technique is not always more effective than 3DCRT. Your radiation oncologist can discuss which treatment techniques are best for your individual case.

Image-guided radiotherapy (IGRT) is another sophisticated development in radiation treatment. This technique uses special daily imaging to make small adjustments at the time of treatment. Pictures similar to an X-ray of a bone or a small CT scan are taken that allow the radiation therapists and physicians to make adjustments to precisely set you up for treatment. This helps deliver radiation to the target and helps decrease the dose to surrounding areas.

Your position for radiation treatment can also help limit how much radiation is received by the heart. For example, being treated on your stomach can shift the breast away from your heart and reduce your risk of hurting the heart.

3-D Treatment Planning

In addition to using 3DCRT to plan your treatment, you may read about or hear your doctor refer to a “dose-volume histogram” (DVH). The dose volume histogram is a computer tool that can be used to determine the dose an organ, such as your heart, will receive. Different studies have published constraints, or limits, that can be used to help determine the risk of heart problems based on the dose the heart receives. By using these techniques, the dose to the heart can be decreased significantly.

Motion Management

Another way of reducing the radiation dose to normal tissue is the use of tools to decrease motion of organs when breathing in and out. For example, if a person has lung cancer, the tumor in the lung will move up and down when the person inhales and exhales. A belt can be applied over the patient’s midsection to help the patient decrease big breaths that result in greater motion. A special type of CT scan is done that can watch the tumor’s movement and account for this breathing in treatment planning. Another technique includes a process called “gating.” This treats only the tumor during certain times in the patient’s breathing cycle. All of these efforts attempt to decrease the amount of radiation to normal tissue.

Another method of limiting radiation cardiotoxicity is called “deep inspiration breath-hold” (DIBH). This can be used for women with left-sided breast cancer to reduce the radiation dose to the heart. Patients are instructed to take a deep breath and hold the breath while they are treated with radiation. This expands the lungs with air and puts a greater distance between the heart and chest wall (the ribs and muscles just under the breast). By increasing the distance from the chest wall, the dose of radiation to the heart decreases. This can also be used in the treatment of certain lung cancer patients.

Radiation Type

Another factor that affects the radiation dose to the heart is what type of radiation is used. There are several radiation types you may have heard about including the most common form, known as “photon” radiation, which uses X-rays to treat your cancer. Additional forms of radiation treatment for cancer may include “proton” or “electron” radiation These forms of radiation have different properties that can be used in an attempt to limit the dose of radiation to your heart.

Proton therapy is a type of radiation available in only a limited number of centers. Using this therapy, radiation to normal tissues can be reduced. However, there is no current clinical data that shows proton therapy reduces cardiotoxicity.

Chemotherapy History

Certain types of chemotherapy affect the heart, including the class of medicines called “anthracyclines” (i.e. daunorubicin, doxorubicin, epirubicin, and idarubicin) and anthracycline-like medicines (i.e. mitoxantrone). When combined with radiation that may involve the heart, there is an increased potential for heart damage, heart failure and side effects.

Other Risk Factors

History of Heart Disease

Patients with underlying medical issues that are risk factors for heart disease, such as diabetes, high blood pressure, smoking, obesity, and high cholesterol, have an increased risk of developing heart disease after receiving radiation.

Studies in cancer patients also suggest that increased physical activity decreases the risk of developing heart disease.

When to Call a Doctor

During radiation treatment, you will see your radiation oncologist at least once a week to watch for any concerning symptoms. Typically, a radiation follow-up will occur between one to three months after completion of your treatment and then may rotate with other health care professionals.

Your radiation oncologist may want to follow up with you every three to six months for the first few years after your treatment ends, or he/she may have you follow up with your other oncologists. The schedule for follow-up appointments depends on your doctor and your type of cancer. Make sure to discuss long-term care before completing your radiation so you understand when you will need to see your doctor.

As always, if you are having severe chest pain at any time, you should seek emergency care and call 112

Exams and Tests

What types of heart tests might you receive before beginning your cancer treatment? Tests may include:

Electrocardiogram (ECG)

An electrocardiogram (ECG) is a picture of your heart’s electrical activity. Some cancer treatment makes certain measurements on an ECG change so you may have more than one ECG during treatment. An ECG can detect abnormal heart rhythms, called arrhythmias.

Studies to Measure Ejection Fraction

In many ways, your heart is a muscle like those in your arms or legs. The muscle of your heart is in the left ventricle. Every time your heart beats, it is expected that a certain amount of blood is pushed out of your left ventricle to the rest of your body with each heartbeat: This is known as your ejection fraction. In general, an ejection fraction of greater than or equal to about 55% is considered normal.

Some cancer treatments can lower your ejection fraction. If you have had chemotherapy or radiation in the area of the heart, you may receive several echocardiograms during treatment, for years after treatment or both. Studies for ejection fraction:

Echocardiogram

Multigated acquisition (MUGA) scan (involves your receiving a radioactive solution given through a vein using an intravenous (IV) line and then having an X-ray taken)

Cardiac MRI

Cardiac Catheterization

During a cardiac catheterization, a thin tube or catheter is guided into an artery, usually in the wrist or leg, and up to the heart. The test goes into the body to directly evaluate the arteries of the heart.

Prevention

What steps can you take to help reduce your risk of developing cardiotoxicity before, during and after radiation therapy? It’s important to take care of your heart:

Make lifestyle changes to improve your heart health

Stop smoking

Control your blood pressure and cholesterol levels

Well-controlled blood pressure is important during cancer treatment, and the goal blood pressure depends on your age and other medical problems. Due to some of the changes that cancer treatment may have on your diet, or other medications such as steroids that may be administered with chemotherapy or radiation treatment, your blood pressure may run higher or lower than usual during treatment. Therefore, it is not uncommon for people to require blood pressure medicine in lower or higher amounts during their cancer treatment.

Your blood pressure will be checked at every appointment during your treatment. If you are concerned that it is too high or too low, you can check your blood pressure at home and bring those readings with you to your appointments.

Radiation can cause atherosclerosis—the buildup of plaque in the arteries of the heart—to occur at a faster rate than would be expected naturally. We know that cholesterol also contributes to the development of atherosclerosis. Your primary health care professional or oncologist can check a fasting cholesterol panel, a type of blood test, and help you decide whether treatment of cholesterol will be helpful to you.

Medicines

Currently, no medications have been shown to protect the heart from side effects of radiation treatment. However, with modern-day techniques aiming to limit cardiac exposure, it is expected that only a small fraction of patients will have long-term side effects of radiation.

Also, medications that treat underlying heart disease (coronary disease, heart failure) and risk factors (high blood pressure, high cholesterol) should be given to patients who also have those conditions.

Limit Exposure

Remember that newer radiation techniques appear to reduce the risk of radiation-induced cardiotoxicity. (See Radiation Techniques in the “Radiation Risks” section.)