Common Side Effects

Common Side Effects

What are the common side effects caused by radiation therapy?

Radiation therapy can cause both early (acute) and late (chronic) side effects. Acute side effects occur during treatment, and chronic side effects occur months or even years after treatment ends. The side effects that develop depend on the area of the body being treated, the dose given per day, the total dose given, individual medical condition, and other treatments given at the same time.

Acute radiation side effects are caused by damage to rapidly dividing normal cells in the area being treated. These effects include skin irritation or damage at regions exposed to the radiation beams. Examples include skin reddening or blistering, mouth soreness and dryness with difficulties swallowing when the head or neck area is treated, or urinary problems when the lower abdomen is treated. Fatigue is a common side effect of radiation therapy regardless of which part of the body is treated. Nausea with or without vomiting is common when the abdomen is treated and occurs sometimes when the brain is treated. Medications are available to help prevent or treat nausea and vomiting during treatment. Most acute effects disappear after treatment ends.

Late side effects of radiation therapy may or may not occur. Depending on the area of the body treated, late side effects can include:

  • Chronic cough and shortness of breath

  • Dry mouth and difficulty swallowing

  • Damage to the bowels, causing diarrhea, bleeding and bowel blockage from adhesions

  • Memory loss

  • Fibrosis (the replacement of normal tissue with scar tissue, leading to restricted movement of the affected area)

Whether or not you experience late side effects depends on other aspects of your cancer treatment in addition to radiation therapy, as well as individual risk factors. Some chemotherapy drugs, genetic risk factors, and lifestyle factors (such as smoking) can also increase the risk of late side effects. If you smoke, the most important thing you can do to reduce your risk of a second cancer is to quit smoking. When suggesting radiation therapy as part of your cancer treatment, the radiation oncologist will carefully weigh the known risks of treatment against the potential benefits (including relief of symptoms, shrinking a tumor, or potential cure). The results of hundreds of clinical trials and doctors’ individual experiences help radiation oncologists decide which patients are likely to benefit from radiation therapy.

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Does radiation therapy cause other cancer?

The risk of developing a second tumor because of radiation therapy is very low. For many people, radiation therapy can cure the cancer. This benefit far outweighs any small risk that the treatment could cause a later cancer. However, you should discuss the risks and benefits of all of your treatments with your treatment team. 

Second cancers that develop after radiation therapy depend on the part of the body that was treated. For example, girls treated with radiation to the chest for Hodgkin lymphoma have an increased risk of developing breast cancer later in life. In general, the lifetime risk of a second cancer is highest in people treated for cancer as children or adolescents.