Updated January 01, 2015.

Radiation pneumonitis is an inflammation of the lungs due to radiation therapy. This side effect of radiation therapy occurs in roughly a fourth of people who go through radiation therapy for lung cancer, but can also result from radiation to the chest for breast cancer, lymphomas, or other cancers.

Symptoms most commonly occur between 1 and 6 months after completing radiation therapy.  With treatment, most people recover without any lasting effects.

Symptoms

It is important to be aware of radiation pneumonitis, because symptoms can be very similar to those caused by lung cancer alone, or can be mistaken for an infection such as pneumonia.
Common symptoms include:

• Shortness of breath that is usually more notable with exercise.
• Chest pain, especially chest pain which worsens with breathing.
• A Cough which can be dry or produce mucous.
• Low-grade fever.

In some cases, no symptoms are present, and the diagnosis is made by its appearance on a chest x-ray alone.

Who is at Risk?

Some people are more at risk than others of developing this condition.  Conditions which increase the risk include:

• Concurrent (meaning at the same time) radiation therapy and chemotherapy.  Radiation pneumonitis (RP) is more common in people receiving concurrent radiation and chemotherapy than those receiving sequential (at different times) radiation and chemotherapy.  If this is alarming it's important to look at factors other than this complication.  In a 2009 study researchers found that people with stage 3 lung cancer who received concurrent radiation and chemotherapy had double the survival after 5 years.  Other studies have also suggested improved survival when the treatments are used together.

• People who have other lung diseases, such as COPD, are at an increased risk.
• Older patients are more likely to develop radiation pneumonitis than younger patients.
• The amount of tissue treated.  The risk of RP increases with the area of the chest that is treated.  It is also more common when the middle and lower lobes of the lungs are treated.
• People who receive the chemotherapy drugs Paraplatin (carboplatin) and Taxol (paclitaxel.)

Cause

Radiation causes the lungs to produce less of the substance surfactant.  Surfactant works to keep the lungs expanded when we exhale and increases the surface area of the lungs available for the exchange of oxygen and carbon dioxide.

Diagnosis

Lab tests may show signs of inflammation, such as an increased white blood cell count. Results of a test that looks for inflammation, called a sed rate, may show non-specific elevations above normal. A chest x-ray can show the characteristic appearance of radiation pneumonitis and may suggest that you need to be treated, even if you are not having any symptoms.

Treatment

Treatment is aimed at decreasing the inflammation. Steroids, such as prednisone, are given until the inflammation subsides and then slowly decreased over time.  Other treatments may be used depending upon the location.  For example, with radiation esophagitis, medications such as proton pump inhibitors, changes in diet, and local anesthetics to help with pain may be used.

Prognosis

Radiation pneumonitis usually resolves with treatment, and is only rarely fatal.  If it goes untreated or persists, it can lead to pulmonary fibrosis (scarring of the lungs), which is often permanent.
<sub>Sources:

Chang, J. et al. Risk factors for radiation pneumonitis in lung cancer. Journal of Clinical Oncology. 2008 ASCO Annual Meeting Proceedings. 26, No 15S(May 20 Supplement):7573.

Dang, J. et al. Risk and predictors for early radiation pneumonitis in patients with stage III non-small cell lung cancer treated with concurrent or sequential chemoradiotherapy. Radiation Oncology. 2014. 9:172.

Kong, F. et al. Non-small cell lung cancer therapy-related pulmonary toxicity: an update on radiation pneumonitis and pulmonary fibrosis. Seminars in Oncology. 2005. 32(2 Suppl 3):S42-54.

Palma, D. et al. Predicting esophagitis after chemoradiation for non-small cell lung cancer: an individual patient meta-analysis. International Journal of Radiation Oncology, Biology, and Physics. 2013. 87(4):690-6.

Palma, D. et al. Predicting radiation pneumonitis after chemoradiation therapy for lung cancer: an international individual patient data meta-analysis. International Journal of Radiation Oncology, Biology, and Physics. 2013. 85(2):444-50.

Yazbeck, V. et al. Management of normal tissue toxicity associated with chemoradiation (primary skin, esophagus, and lung). Cancer Journal (Sudbury, Mass). 2013. 19(3):231-7.</sub>