Side Effects of Radiation Therapy

Approved by the Cancer.Net Editorial Board, 11/2015

Radiation therapy treats many types of cancer effectively. But like other treatments, it often causes side effects. These are different for each person. They depend on the type of cancer, location, doses, and your general health.

Why does radiation therapy cause side effects?

High doses of radiation are used to destroy cancer cells. Side effects occur because radiation can also damage healthy cells and tissues near the treatment area. Today, major advances in radiation technology have made it more precise, leading to fewer side effects.  

For some people, radiation therapy causes few or no side effects. For others, the side effects are more severe. Reactions often start during the second or third week of treatment. Also, they may last for several weeks after the final treatment.

Can side effects be prevented or treated?

Yes. Your health care team can help you prevent or treat many side effects. Preventing and treating side effects is now an important part of cancer treatment. It is part of a type of care called palliative care.

Common general side effects

Radiation therapy is a local treatment. Therefore, it only affects the area of the body where the tumor is located. For example, people do not usually lose their hair from having radiation therapy. This is only true if the radiation is aimed at a part of the body that grows hair, such as the scalp.

Skin problems. Many people who receive radiation therapy experience dryness, itching, blistering, or peeling. These issues usually stop a few weeks after treatment has finished. If skin damage becomes a serious problem, the doctor may change your treatment plan.

Fatigue. Fatigue is feeling tired or exhausted almost all the time. Your level of fatigue depends on whether you are having other treatments, such as chemotherapy. Learn more about how to cope with fatigue.

Long-term side effects. Most side effects go away after treatment. But some continue, come back, or develop later. These late effects may include developing a second cancer. However, the risk of having a second cancer because of radiation therapy is low. This risk is often smaller than the benefit of treating the primary, existing cancer. 

Side effects specific to where the radiation therapy is given

In addition to general side effects, some side effects of therapy depend on the type and location of the radiation.

Head and neck. If radiation therapy is aimed at a person’s head and/or neck, they may experience the following side effects:

  • Dry mouth

  • Mouth and gum sores

  • Difficulty swallowing

  • Stiffness in the jaw

  • Nausea

  • A type of swelling called lymphedema

  • Tooth decay. Learn more about dental health during cancer treatment.

Chest. Radiation therapy aimed at the chest may cause the following side effects:

  • Difficulty swallowing

  • Shortness of breath

  • Breast or nipple soreness

  • Shoulder stiffness

  • Cough, fever, and fullness of the chest called radiation pneumonitis that happens between two weeks and six months after radiation therapy

  • Radiation fibrosis, which is permanent scarring of the lungs from untreated radiation pneumonitis. The radiation oncologist knows how to minimize the risk of fibrosis in the planning process.

Stomach and abdomen. Radiation therapy aimed at the stomach or abdomen may cause the following side effects:

  • Nausea and vomiting

  • Diarrhea

These symptoms will likely disappear after treatment. Your doctor can prescribe drugs for these side effects, and making changes to your diet may also reduce your discomfort.

Pelvis. Radiation therapy aimed at the pelvis may cause the following side effects:

  • Diarrhea

  • Rectal bleeding

  • Incontinence

  • Bladder irritation

In addition, radiation therapy to the pelvis can cause different symptoms for men and women.

For men:

  • Sexual problems, such as impotence, which is the inability to get or maintain an erection

  • Lowered sperm counts and reduced sperm activity from radiation therapy to the testes or prostate. This may affect the ability to father a child. Learn about ways to preserve your fertility.

For women:

  • Changes in menstruation, such as stopping menstruating

  • Symptoms of menopause, such as vaginal itching, burning, and dryness

  • Infertility, which is the inability to conceive a child or maintain a pregnancy, if both ovaries receive radiation. Learn about ways to preserve your fertility.

Coping with side effects

Everyone’s experience with cancer treatment is different. Talk with your doctor or nurse about which side effects you may or may not develop before treatment begins. It is also important to continue talking with your health care team throughout your treatment schedule. There are many options for managing side effects. Your doctors and nurses need to know you are experiencing them in order to help you feel better.

More Information

Side Effects

Coping with the Fear of Treatment-Related Side Effects

Additional Resources

National Cancer Institute: Radiation Therapy Side Effects

RT Answers: Side Effects