What are the side effects of radiation therapy?

Abramson Cancer Center of the University of Pennsylvania
Last Modified: December 4, 2015

The side effects of radiation therapy vary from patient to patient. Most patients have only mild side effects that are easily managed.

There are two main types of side effects: acute and chronic. Acute side effects occur during the treatment phase and typically go away a few weeks after treatment is finished. They include fatigue, skin reactions, and side effects specific to the area being treated.

The most common acute side effect of radiation therapy is fatigue, a sense of tiredness or general weakness. It is believed to be caused by the tremendous amount of energy that is used by the body to heal itself in response to radiation therapy.

Most people begin to feel fatigued about 2 weeks after radiation treatments begin. The tired feeling goes away gradually after the treatment is finished. Normal levels of energy generally return a few weeks after completing treatment, but can take as long as a year, particularly if you received chemotherapy as well. For more information on fatigue, go to Side Effect: Fatigue.

In addition to fatigue, many patients that receive radiation therapy develop a skin reaction. Each time radiation therapy is delivered, small amounts are absorbed by the skin over the area being treated. About 2 to 3 weeks after your first radiation treatment, you may notice redness and irritation similar to a sunburn. These changes are an expected part of your therapy and are temporary. For more information on skin reactions, go to Side Effect: Skin reactions.

The other acute side effects of radiation therapy are specific to the area being treated. For example, patients receiving radiation therapy to the stomach or abdomen may have diarrhea and nausea and vomiting, whereas patients receiving treatment to the head and neck area may develop mouth sores. Only patients receiving radiation therapy to the head experience hair loss, called alopecia. Your radiation oncologist and nurse will give you specific instructions on what you can do to help prevent or minimize these side effects. For additional information see the Radiation Side Effects Menu.

Chronic side effects occur months to years after radiation therapy. They differ according to the area treated and the total dose of radiation therapy received, and may be permanent. During your initial consultation, your radiation oncologist will discuss with you any side effects that you may experience as a result of the radiation therapy treatment planned for you. You are encouraged to take this information into consideration when making decisions about your treatment.