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Lung Radiation Side Effects

Normal lung tissue is sensitive to radiation and can be injured. If the radiation just inflames the lung it is called radiation pneumonitis. See the  review articles about radiation pneumonitis here and here. If the lung tissue is more damaged it may be replaced by scar tissue (called radiation fibrosis).

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The side effects of radiation to the lung region are related to how large the radiation field (the larger, the more side effects) how much normal lung is in the way (the more normal lung, the more scar tissue or fibrosis) what other structures are in the way (if the tumor is near the esophagus, then a sore throat or swallowing problems would be more likely) and whether the patients is also getting chemotherapy (which increase the frequency and severity of side effects.)

Radiation can definitely inflame/damage normal lung tissue in the way (see pictures of radiation pneumonitis here, here, here and here, radiation chest wall inflammation here and radiation fibrosis here).

There are limits to the safe doses of radiation (go here, here, here, here and here) which basically recommend keeping the total lung volume that gets 20Gy (V20) below 25% or the V10 below 40% and  the mean lung dose under 20Gy. Recent review on safe doses go here.

See the NCCN guidelines here) and here

New techniques are being used to evaluate the functional parts of the lung (go here).

The  PET shows a complete remission (no evidence of cancer) at 14 months. The cancer was 'hot' on the first two pictures (meaning the cancer cells are alive and consuming a  lot of glucose, called hyper-metabolic)  but now there is only some radiation fibrosis (the gray tissue, no longer yellow or hyper-metabolic) ) that is typical after high dose radiation, also note that the left lung cavity looks smaller (called volume loss) again this is  due to some scarring and shrinkage from the radiation effects


Typical side effects are listed in the consent form below from the recent RTOG lung trial
Short term there is little risk from radiating the heart (though the dose should be limited as noted here) but long term there is an increased risk of coronary artery disease (see here.)

Consent form for RTOG 0324    Risks from Radiation Therapy
Radiation therapy to the chest
Very Likely
Difficulty, pain, or burning sensation when swallowing, which is temporary; the use of chemotherapy withradiation may increase this risk. You should avoid acidic or spicy foods and alcoholic beverages.
Fatigue (tiredness) for no apparent reason, which is temporary
The skin in the treatment area may become reddened and/or dry, and chest hair may not grow back.
Decrease in blood counts while undergoing treatment, which could lead to an increased risk of infection, weakness, and/or in bleeding and bruising easily Cough
Some difficulty breathing, due to lung damage, as described below

Less Likely, But Serious
 Irritation of the lining around the heart, which can cause chest pain, shortness of breath, and irregular or rapid heart beat; rarely, this can require surgery to correct.
 Irritation and/or damage to the muscle of the heart; rarely, this can cause a heart attack, heart failure, and/or death.
 Irritation and/or damage to the spinal cord (the major nerve within the spine), which can lead to weakness, tingling or numbness of the lower body and legs; very rarely, this can lead to inability to move or control the lower half of the body.
 Narrowing of the esophagus (tube to the stomach)

Chest radiotherapy can cause changes in normal lungs. These changes can be as unimportant as small amounts of "scarring" seen on x-rays that does not cause symptoms. Sometimes chest radiotherapy can cause lung damage that leads to symptoms such as shortness of breath, cough, or fever. Rarely, these symptoms can be severe or life threatening. The combined use of chemotherapy and radiotherapy, as in this study, may increase the risk of developing symptoms due to lung damage.

 

Radiation to the lung causes scar tissue (or fibrosis) of  the lung alveoli and can decrease the function of the lungs. This can be measured by pulmonary functions tests as shown below

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