What is radiation pneumonitis?

Radiation pneumonitis is a type of lung injury. While pneumonia is caused by bacteria or viruses, pneumonitis is caused by an irritant, similar to an allergy. Radiation pneumonitis happens to some people after they’ve received radiation treatments to their lungs or chest area. Between 5 and 15 percent of people receiving radiation treatment for lung cancer develop pneumonitis. However, anyone receiving radiation therapy to the chest can develop it.

While it tends to happen about 4 to 12 weeks after radiation treatment, it can develop as early as 1 week after treatment. In other cases, it develops very slowly over the course of several months.

The main symptoms of radiation pneumonitis include:

These symptoms are very similar to those of both pneumonia and lung cancer. In addition, radiation therapy can cause similar side effects, even in people who don’t develop radiation pneumonitis. As a result, many people ignore these symptoms and don’t get treatment.

If you’ve undergone radiation therapy within the last few months and notice these symptoms, tell your doctor as soon as possible.

Radiation therapy works by killing or damaging cancerous cells. During this process, it can also irritate other structures, including noncancerous cells and tissue. In the case of radiation pneumonitis, it causes inflammation of the small air sacs, called alveoli, in your lungs. This makes it harder for oxygen to pass through your alveoli and into your bloodstream.

Some people are more likely than others to develop radiation pneumonitis after radiation treatment. The biggest factor involves the size of the area receiving radiation treatment. The larger the area, the higher the risk of developing radiation pneumonitis. However, some newer, computer-assisted radiation techniques reduce this risk by delivering radiation more precisely.

Other things that can increase your risk include:

  • receiving higher doses of radiation
  • having poor lung function prior to treatment
  • being female
  • being older
  • smoking

In addition, taking chemotherapy drugs while receiving radiation therapy can also increase your risk. Chemotherapy drugs that may increase your risk include:

  • actinomycin D
  • cyclophosphamide
  • vincristine
  • bleomycin
  • methotrexate
  • mitomycin
  • doxorubicin

Radiation pneumonitis is hard to distinguish from other conditions, including pneumonia and lung cancer itself. There’s no test to determine whether or not you have it, so your doctor will likely start by ruling out other causes before making a diagnosis.

To do this, they’ll need to do some additional tests, including:

  • Chest X-ray. This test gives your doctor a basic view of your lungs. Radiation pneumonitis often causes a cloudy area to show up in chest X-rays.
  • Chest CT scan. This computer-guided X-ray provides a 3-D image of your lungs, which can offer additional information that an X-ray can’t.
  • Chest MRI scan. An MRI provide a highly detailed image that your doctor can use to get a better look at anything they found during an X-ray or CT scan. MRI scans are particularly helpful for distinguishing between pneumonitis and changes in cancerous tumors.
  • Pulmonary function test. This test uses a spirometer to measure the amount of air that goes in and out of your lungs. It gives your doctor a better idea of how well your lungs are functioning.

Treatment for radiation pneumonitis depends on how severe the condition is. For most people, symptoms clear up on their own within 7 to 10 days of appearing. However, more severe cases require aggressive treatment.

The most common treatment for severe pneumonitis is a long course of corticosteroids, such as prednisone. These are powerful anti-inflammatory medications that can reduce inflammation in your lungs by suppressing your immune system. Keep in mind that this can also increase your risk of developing an infection, so your doctor may give you additional advice for protecting yourself against infections while taking them.

Depending on your symptoms, you may also need oxygen therapy to improve your breathing. This involves administering additional oxygen through either a face mask or small tubes through your nostrils.

Other treatments for radiation pneumonitis include:

Radiation pneumonitis can have some lasting effects, especially in more severe cases that aren’t treated. Over time, it can develop into radiation fibrosis if your symptoms don’t improve. This refers to permanent scarring of your lung tissue. It usually starts to happen 6 to 12 months after radiation treatment, but it can take as long as 2 years to fully develop.

The symptoms of radiation fibrosis are similar to those of pneumonitis, but they’re usually more severe. If you have radiation pneumonitis that feels like it’s getting worse, your doctor may check for signs of fibrosis.

Most people recover from radiation pneumonitis within one or two weeks. If you need to take corticosteroids, you might see a major reduction in your symptoms within a day or two.

As you heal, there are also things you can do to help manage your symptoms, including:

  • drinking plenty of fluids to keep your throat moist
  • using a humidifier to add moisture to the air
  • sleeping on extra pillows to raise your upper body and make breathing easier
  • staying inside on very cold or hot and humid days, which can irritate your lungs
  • resting as soon as you feel short of breath

Radiation pneumonitis is a risk for anyone undergoing radiation treatments to the chest. While many cases resolve in a week or two, some eventually become radiation fibrosis, which causes permanent scarring. If you’ve recently undergone radiation treatment or plan to, make sure you know how to recognize the symptoms of radiation pneumonitis so you can begin treatment as early as possible if you need it.