One of the side effects of radiation therapy (also called radiotherapy) involves the lungs. When high-energy rays are used to damage cancer cells and stop them from growing and dividing, it is inevitable that normal cells are also affected.
Especially after radiation treatments for tumors within the chest or the breast, the lungs may become inflamed. The lung inflammation from radiotherapy is termed radiation pneumonitis.
Radiotherapy is usually given on an outpatient basis in a hospital or clinic 5 days a week for several weeks. Radiation pneumonitis tends to show up 2 weeks to 6 months after the end of radiotherapy.
By no means is everyone with radiation pneumonitis ill. The radiation pneumonitis may be seen as an incidental finding on a chest x-ray in someone who had radiotherapy but has no symptoms.
Blood testing usually shows an abnormal white blood count and an elevated sedimentation rate, signs that inflammation may be present somewhere in the body, but not pointing specifically at the lungs.
If radiation pneumonitis persists, it can lead to scarring of the lungs, a condition called radiation fibrosis.
Radiation fibrosis typically occurs a year after the completion of radiation treatments. Radiation fibrosis is usually not reversible.