What Is Radiation Pneumonitis?

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Radiation pneumonitis (RP) is an inflammation of the lungs due to radiation therapy or stereotactic body radiotherapy (SBRT) for cancer. Radiation pneumonitis affects between 15% and 40% of people who undergo radiation therapy for lung cancer. It may also develop in patients who undergo chest radiation for breast cancer, lymphomas, thymic tumors, or esophageal cancer.

Older woman with shortness of breath
Patrick Heagney / E+ / Getty Images

Radiation Pneumonitis Symptoms

Radiation pneumonitis symptoms can be very similar to lung cancer symptoms or side effects from other cancer treatments, or they can be mistaken for an infection such as pneumonia. Thus, many people disregard or miss these common signs of RP:

  • Dyspnea: Shortness of breath that is more pronounced with physical exercise
  • Hypoxemia: Low oxygen levels in your blood, which can cause confusion and increased heart rate
  • Low-grade fever: Persistent fever below 100.4 degrees F
  • Dry cough: Frequent cough with no phlegm or mucous

These symptoms may appear as little as a month after radiation or may not develop until a year later, but most cases are diagnosed within eight months of treatment.

Often, the symptoms are mild enough for people to tolerate and recover with no need for additional medical treatment. In other cases, symptoms can be serious and result in severe respiratory problems, including acute respiratory distress syndrome, a potentially life-threatening condition.

This is a good reminder that you should talk to your oncologist about any symptoms related to your breathing or your health overall after lung cancer treatment. Don't assume that a problem is just a side effect that you need to live with. It may be a complication that your healthcare provider can treat.


While radiation can stop your cancer by killing malignant cells, it can also damage healthy cells. Specifically, radiation causes the loss of cells that secrete pulmonary surfactant, a chemical that keeps the alveoli, or lung's air sacs, open so that they can fill with air and efficiently regulate breathing.

A lack of surfactant often results in respiratory distress. You may already have familiarity with this effect if you've known a premature infant with breathing difficulties.

Not everyone who undergoes thoracic (chest) radiation has a problem with surfactant levels, and not all those who have a problem with surfactant levels develop serious respiratory problems.

Several factors, however, can put you at risk for complications:

  • Chemoradiation: Receiving chemotherapy concurrently (at the same time) as radiation therapy raises the likelihood that you'll develop radiation pneumonitis.
  • Gender: The risk of RP is estimated to be 15% in women versus 4% in men.
  • Age: Lung cancer patients over age 65 are more susceptible to radiation pneumonitis.
  • Tumor location: Several studies have shown that RP is more common when radiation is used on lower lung lobes versus higher lobes.
  • Lung function: People who have other lung diseases, such as COPD, are at an increased risk.
  • Type of chemotherapy drugs (if applicable): Paraplatin (carboplatin) and Taxol (paclitaxel) are more likely to lead to this specific pulmonary complication.

While concurrent radiation and chemotherapy may increase your risk for radiation pneumonitis, studies show that the combined treatment can improve five-year survival rates in those with non-small cell lung cancer. Be sure to discuss all the pros and cons with your healthcare provider and weigh your options carefully before ruling out radiation.

Smoking and Reduced RP Risk

While smoking is a clear risk of developing lung cancer, it seems to actually offer some protection against developing radiation pneumonitis. That is, those who continue to smoke after radiation are less likely to report symptoms.

It's unclear if nicotine actually offers some protection or if smokers, who tend to already have pulmonary symptoms before radiation, are less likely to recognize and report symptoms.

Regardless, continuing to smoke during and/or after lung cancer treatment is not advised due to the numerous health risks it imposes.


There is no specific diagnostic test to confirm radiation pneumonitis. Instead, your healthcare provider will make a clinical diagnosis based on symptoms.

The analysis might include the following:

  • Blood tests that look for signs of infection or inflammation in the blood, such as an increased white blood cell count
  • Pulmonary function tests (PFTs) to assess reduced lung volumes or stiffness of the lungs
  • Swab test of the throat to look for infection
  • Sputum (mucous) culture to check for bacteria
  • Chest X-ray that may reveal changes to the parts of the lung that were exposed to radiation
  • Computed tomography (CT) scan, which may offer a clearer picture of lung tissue that had been subjected to radiation therapy

Differential Diagnoses

Because RP's symptoms are so similar to those of other lung conditions, your healthcare provider will use the results of tests and an examination to rule out other possible causes, including:

  • Pneumonia
  • Pulmonary emboli, blood clots that usually start in the legs, break off, and travel to the lungs
  • Spread of cancer to other parts of the lung or the other lung


Radiation pneumonitis treatment is aimed at decreasing the inflammation. Corticosteroids, such as prednisone, are the main course of treatment.

Typically, your healthcare provider will treat you with 60 milligrams (mg) to 100 mg per day for two weeks and then lower the dosage, tapering you off the medication over three to 12 weeks.

Researchers have also been looking at ways to use targeted therapies to treat the problem. However, studies have yet to find a proven effective treatment.


While radiation pneumonitis can sometimes lead to serious respiratory distress, in the vast majority of cases, it is not a deadly condition. The risk of dying from RP is less than 2%.

Thus, with proper treatment, you should be able to overcome radiation pneumonitis. However, if it goes untreated, RP can lead to pulmonary fibrosis, scarring of the lungs. This condition, which can make breathing very difficult, is one of the known side effects of radiation therapy.


Researchers are looking for ways to reduce the risk of radiation pneumonitis among people going through radiation for lung cancer. For those who will be having SBRT, a positive development has been the use of the antibiotic Biaxin (clarithromycin), which seems to significantly reduce the severity of RP and may actually prevent it from developing.

Another area being researched is the association between decreased risk for RP and the consumption of soy isoflavone (soy-based foods such as tofu). It seems that soy decreases inflammation while posing no threat to the effectiveness of radiation therapy in eliminating cancer cells. You should discuss this with your radiation oncologist before making changes to your diet.

A Word From Verywell

Radiation pneumonitis is very common in people who are treated for cancers such as lung cancer and breast cancer. Thankfully, with treatment, the condition often resolves without going on to cause life-threatening problems. The most important thing you can do is be aware of the possible symptoms and talk to your healthcare provider if you experience any of them.

8 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading

By Lynne Eldridge, MD
 Lynne Eldrige, MD, is a lung cancer physician, patient advocate, and award-winning author of "Avoiding Cancer One Day at a Time."