Radiation therapy — which destroys cancer cells — can effectively treat breast cancer after a lumpectomy or mastectomy. Because the heart and lungs are located near the breast and chest wall, radiation can sometimes affect these organs as well.

Some heart and lung complications can develop within weeks or months of treatment, while others may not appear for many years — sometimes up to 20 years later. Knowing what to watch for can help you recognize possible symptoms and get care when needed.

If you’ve had radiation therapy for breast cancer, your doctor will monitor you for possible side effects during follow-up visits. Let your oncologist or healthcare team know about any new or unusual chest symptoms. Below are five ways breast cancer radiation may affect the heart and lungs.

🗳️ Have you experienced any heart or lung complications after radiation therapy for breast cancer?

Yes, heart complications

Yes, lung complications

Yes, both heart and lung complications

No, I haven’t

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Pneumonitis is inflammation or irritation of the lung that isn’t infectious. A 2023 study found that 38 percent of people who received radiation therapy for breast cancer developed pneumonitis of any grade (2 percent of these were asymptomatic or grade 1 pneumonitis).

Symptoms of pneumonitis include:

Treatment options include oral corticosteroids and oxygen therapy.

The risk of pneumonitis increases with higher doses of radiation. Smoking, age, and treatment in combination with the drugs goserelin (Zoladex) and tamoxifen are also risk factors.

Pneumonitis usually develops short-term, within weeks to months of radiation therapy. It can potentially lead to pulmonary (lung) fibrosis — scarring and hardening of connective tissue in the lungs. Fibrosis occurs later in the course of lung disease.

If you have asthma or other types of chest problems, your symptoms may worsen due to pneumonitis. Always discuss any preexisting lung conditions with your radiation oncologist and healthcare providers if you’re planning to have radiation treatment.

About 10 percent to 15 percent of people who have radiation for breast cancer develop radiation-induced lung fibrosis — only 1 percent to 5 percent are symptomatic. Symptoms include dry cough and shortness of breath.

Lung fibrosis progresses over time, although many people live actively with the condition. Treatment options include oxygen therapy, lung rehab programs, and medications to reduce symptoms such as inflammation.

Radiation therapy for breast cancer may slightly increase the risk of developing lung cancer later in life. A large 2023 study found that, compared with people who didn’t have radiation, the risk of lung cancer was 14 percent higher five to nine years after treatment. It was 28 percent higher after 10 years and 30 percent higher after 15 years.

This risk may increase over time and is higher in people who smoke. Using lower radiation doses and techniques such as deep-inspiration breath hold (DIBH) may help lower exposure to nearby organs.

During DIBH, you take and hold a deep breath while the radiation is given. Talk with your doctor about your personal lung cancer risk and ways to reduce it.

Radiation therapy may cause a number of different heart conditions. Higher amounts of radiation can further increase those risks. The risk is also higher when radiation treatment is left-sided, which is nearer to the heart.

In one study of women aged 55 and under living with breast cancer, 10.5 percent of those who received left-sided radiation treatment developed coronary artery disease (CAD), the most common form of heart disease in the U.S.

By comparison, only 5.8 percent of those who received right-sided radiation therapy developed CAD. Notably, that 5.8 percent is in line with the prevalence of CAD among women aged 20 and over in the U.S., according to the Centers for Disease Control and Prevention.

Short-Term Heart Complications

People who’ve undergone radiation therapy have a higher risk of developing short-term pericarditis — inflammation of the pericardium (sac) that surrounds the heart. Symptoms include:

Pericarditis is often treated with rest and nonsteroidal anti-inflammatory drugs (NSAIDs) or other anti-inflammatory medication. Most people make a full recovery.

In pericardial effusion, fluid collects in the pericardium, which can cause heart damage and be life-threatening. Symptoms include:

The condition can be treated with anti-inflammatory medication or, in more serious cases, by draining fluid with a needle or surgery.

Long-Term Complications

Some types of radiation-induced heart disease can develop over years and may be serious, including:

Factors that increase your risk for heart complications following radiation therapy include:

Smoking, excessive alcohol consumption, and high body weight are all highly detrimental to heart health.