Respiratory Gating for Radiation Therapy With Breast Cancer

Protecting Your Heart From Radiation With Left-Sided Breast Cancer

woman with pink breast cancer bracelets holding her arms crossed over her chest
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Radiation therapy can improve the survival rate for some people with breast cancer but has the potential to damage your heart if you have left-sided breast cancer. Radiation therapy to your heart may also be cumulative with damage caused by other cancer treatments such as chemotherapy and targeted therapies. Learn how the breathing technique of respiratory gating and breath hold may significantly reduce the amount of radiation which hits your heart, and in doing so lower your risk for heart disease.

Radiation Therapy for Breast Cancer

Many women go through radiation therapy for breast cancer, and currently, roughly 50 percent of people with early-stage breast cancer have these treatments. Radiation therapy to the breast may be used to reduce the risk of a local recurrence in the breast after a lumpectomy. It also reduces the breast cancer death rate by one-sixth.

Radiation may also be used after a mastectomy, especially in women who have lymph nodes positive for the disease. Whole breast radiotherapy is given on different schedules depending on the cancer center but often takes place daily during the week for five to six weeks. Newer methods of radiation also offer higher doses of radiation with fewer visits at some centers.

Radiation Therapy and Heart Disease

With the survival rate for breast cancer improving due to better chemotherapy combinations, continued hormone therapy for five to 10 years, and targeted therapies for HER2 positive disease, the risk of living longer with cancer needs to be addressed.

In the past, we were not as concerned about the long-term side effects of radiation therapy as we are today. Many people can be expected to live several decades after these treatments causing us to take a serious look at potential complications which may occur years down the road.

Radiation therapy has been implicated in several different types of heart disease.

These include:

  • Coronary artery disease
  • Cardiomyopathy/congestive heart failure, a weakening of the heart muscle which reduces the ability of the heart to pump blood to the rest of the body
  • Diseases involving the valves of the heart (valvular heart disease)
  • Abnormal heart rhythms (arrhythmias)
  • Pericardial conditions: Damage to the lining of the heart (the pericardium) can lead to a built up of fluids between the tissue layers called a pericardial effusion. A pericardial effusion makes it more difficult for the heart muscle to pump and can sometimes be a medical emergency.
  • Sudden cardiac death

Studies have found that reducing the amount of radiation which reaches the heart during treatments appears to reduce the risk of cardiac toxicity (heart damage), but how important is this?

A large 2017 review looked at the risk of heart-related deaths in women diagnosed with breast cancer between 2010 and 2015. From this data as well as other studies, researchers tried to estimate the impact of radiation therapy on future heart disease and compare this with the benefits of radiation in reducing recurrence and breast cancer-related deaths.

It was found that the benefits of radiation therapy on breast cancer survival outweighed the estimated risk of heart disease related to radiation.

There was one exception, however, and in people who smoke the risk of radiation-related heart disease may outweigh its benefits for cancer. Altogether, radiation therapy was estimated to increase the risk of heart disease by around 30 percent.

Respiratory Gating: Does It Work?

Respiratory gating is a method of changing the shape of the chest in order to minimize exposure of the heart to radiation. Respiratory gating and breath hold radiation therapy are a technique in which a person takes a large breath of air and holds it while the radiation beam is directed at the breast. This breast holding is required for around 20 to 30 seconds, repeated several times during each radiation therapy visit.

According to a 2016 study, the deep inspiration breath-hold technique reduced the amount of radiation the heart received (mean heart dose) by about 50 to 60 percent relative to the heart dose of radiation in people who breathed normally and spontaneously throughout the session. Some people were able to control their breathing enough that there was minimal to no radiation reaching their heart. There are several variations of the technique including Active Breathing Control or the ABC system.

Other techniques have been tried to reduce the dose of radiation delivered to the heart, but often result in a lower (and less protective) amount of radiation being delivered to the breast tissue and chest wall.  With respiratory gating and breathe hold, radiation oncologists were able to reduce the impact on the heart without having to reduce the dose of radiation.

What Can You Expect During Your Treatments?

The first step in respiratory gating will be your treatment planning with your radiation oncologist to determine where radiation will be given and at what dose (called a dosimetric plan). During this planning stage, your radiation oncologist will make measurements and test the ability of respiratory gating to lower the amount of radiation delivered to your heart.

The procedure is tolerated quite well and roughly 80 percent of people are able to control their breathing and hold their breath for the amount of time needed. Some people have pictured themselves swimming a lap in a pool underwater as they do the breathing. During your session, a feedback system such as audio-visual biofeedback is often set up to tell you when to breathe normally and when to hold your breath. 

Limitations of Respiratory Gating and Breath Hold

As noted earlier, respiratory gating is usually well tolerated and many people are able to hold their breath for the duration of time needed. There are some limitations, however, and it was found that some people (less than 20 percent) found it difficult to keep their inspiration level within the particular range chosen.

Other Cancer Treatments Associated With Heart Disease

Radiation therapy for left-sided breast cancer may increase the risk of heart disease, but other breast cancer treatments may add to that risk.

Chemotherapy drugs for breast cancer may increase your risk of heart disease, particularly cardiomyopathy and heart failure, and your oncologist may have had you do heart tests (such as a MUGA scan) prior to beginning chemotherapy. Adriamycin (doxorubicin) is a well-known risk factor for heart failure and is used in many chemotherapy regimens for early-stage breast cancer. Cytoxan (cyclophosphamide) may also have heart-related side effects.

For women with HER2 positive breast cancer targeted drugs such as Herceptin (trastuzumab) and related drugs may be used. Roughly 5 percent of people treated with HER2-targeted therapies will experience some degree of heart failure. It is more likely to occur when combined with Adriamycin and likely adds to the cardiac risk posed by radiation therapy. Severe cardiotoxicity is somewhat lower and ranges from 0.6 to 4 percent.

For women with estrogen receptor-positive tumors, hormonal treatments for breast cancer may raise the risk of heart disease as well. Medications known as aromatase inhibitors, including Aromasin (exemestane), Arimidex (anastrozole), and Femara (letrozole), are often used for women with postmenopausal breast cancer following chemotherapy and for women with premenopausal breast cancer who have received ovarian suppression therapy.

Surgery for breast cancer doesn't appear to increase the risk of heart disease, but pain or achiness related to surgery may reduce your ability to recognize the symptoms of heart disease.

Talking to Your Doctor About Your Risk Factors for Heart Disease

While you are going through breast cancer treatment your mind is probably focused on breast cancer alone. Yet heart disease is the leading cause of death in women, and of heart disease, coronary artery disease is most common.

It's important to talk to your doctor about the risk of heart disease related to your breast cancer treatments. In addition to breast cancer treatments, other risk factors for heart disease in women may include:

  • Personal or family history of heart disease
  • Smoking
  • High blood pressure
  • Elevated cholesterol (or low HDL)
  • Overweight or obese
  • Diabetes or metabolic syndrome

Your doctor may also wish to do a blood test called a C-reactive protein (CRP). Depending on your history, risk factors, and cancer treatments, further testing may be recommended.

Know the Warning Signs of Cardiac Problems—They Are Different in Women!

In recent years, we've learned that cardiac symptoms in women often differ from those in men. This is true for heart failure as well as coronary artery disease and is thought to be one of the reasons that coronary artery disease can be more severe in women. Women who have a heart attack have longer hospitalizations for heart disease overall and are more likely to die before leaving the hospital. It's important to understand the possible reasons for this.

Heart failure related to cardiomyopathy in men often includes progressive shortness of breath and coughing up a foamy pinkish discharge from the lungs. Symptoms of heart failure in women

can be more subtle. Symptoms may include fatigue, shortness of breath which may be described as more of an exercise intolerance, and swelling of the feet and ankles.

The same is true with angina and heart attacks. Men tend to have the more classic symptoms of crushing chest pain like an elephant sitting on their chest. Angina in women often includes symptoms of nausea and vomiting, indigestion, shortness of breath, or severe and profound fatigue. While some women have "typical" symptoms of a heart attack, the symptoms of a heart attack in women often differ from those in men as well.  Women may have a hot and burning sensation in their chest, or even tenderness to touch. Minor symptoms often occur for three to four weeks prior to the heart attack in retrospect. Women may have no chest pain at all when they have a heart attack! Since heart attacks at home are more common in women, the risk of sudden death is higher as well.

"Silent" heart attacks are defined as those that are found on testing (such as an electrocardiogram) but occurred without any symptoms. These silent events are more common in women.

To complicate matters further, both women who have breast cancer and their physicians are more likely to think of a possible breast cancer complication than the real possibility that these symptoms could represent heart disease. Many of these symptoms are first attributed to the cancer and only later found to be related to heart disease.

Bottom Line on Respiratory Gating to Reduce Heart Disease From Radiation Therapy

After learning about heart disease in women, as well as other cancer treatments which may confer risk, it's easier to understand why reducing the exposure of your heart during radiation therapy for left-sided breast cancer might be important.

Respiratory gating can reduce the amount of radiation delivered to the heart but 50 to 60 percent, and sometimes eliminate this exposure altogether. Most of the time these breathing techniques are well-tolerated and may even give you "something to do" during your radiation sessions.

Not all radiation oncology centers offer this technique, but it becoming much more common around the country. Given the number of side effects related to treatment, it is also refreshing to have a technique which has little risk.

Finally, though breast cancer is probably in the forefront of your mind, it is heart disease which kills more women, including many women who were treated for breast cancer. Talk to your doctor about your risk factors and any further testing that might be recommended. And make sure you are familiar with the "atypical" symptoms of heart disease which are common to women. Women are more likely to suffer sudden death, spend more time in the hospital, and die before leaving the hospital than men who have heart disease, one reason being that it's not as high on the radar screen for women or their doctors.

Sources:

Boda-Heggermann, J., Knopf, A., Simeonova-Chergou, A. et al. Deep Inspiration Breath Hold-Based Radiation Therapy: A Clinical Review. International Journal of Radiation Oncology, Biology, and Physics. 2016. 94(3):478-92.

Schonecker, S., Walter, F., Freislederer, P. et al. Treatment Planning and Evaluation of Gated Radiotherapy in Left-Sided Breast Cancer Patients Using the Catalyst/Sentinel System for Deep Inspiration Breath-Hold (DIBH). Radiation Oncology. 2016. 11:143.

Taylor, C., Correa, C., Duane, F. et al. Estimating the Risks of Breast Cancer Radiotherapy: Evidence From Modern Radiation Doses to the Lungs and Heart and From Previous Randomize Trials. Journal of Clinical Oncology. 2017. 35(15):1641-1649.

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