Side Effects of Radiation Therapy

Approved by the Cancer.Net Editorial Board, 12/2018

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, its location, the radiation therapy dose, and your general health.

Why does radiation therapy cause side effects?

High doses of radiation therapy are used to destroy cancer cells. Side effects come from damage to healthy cells and tissues near the treatment area. Major advances in radiation therapy have made it more precise. This reduces the side effects.

Some people experience few side effects from radiation therapy. Or even none. Other people experience more severe side effects.

Reactions to the radiation therapy often start during the second or third week of treatment. They may last for several weeks after the final treatment.

Are there options to prevent or treat these side effects?

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

Potential side effects

Radiation therapy is a local treatment. This means that 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. But radiation therapy to the scalp may cause hair loss.

Common side effects of radiation therapy include:

Skin problems. Some people who receive radiation therapy experience dryness, itching, blistering, or peeling. These side effects depend on which part of the body received radiation therapy. Skin problems usually go away a few weeks after treatment ends. If skin damage becomes a serious problem, your doctor may change your treatment plan.

Fatigue. Fatigue describes feeling tired or exhausted almost all the time. Your level of fatigue often depends on your treatment plan. For example, radiation therapy combined with chemotherapy may result in more fatigue. 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 are called late effects. One example is the development of a second cancer. This is a new type of cancer that develops because of the original cancer treatment. The risk of this late effect is low. And the risk is often smaller than the benefit of treating the primary, existing cancer.

Site-specific side effects of radiation therapy

Some side effects depend on the type and location of radiation therapy.

Head and neck. Radiation therapy aimed at a person’s head or neck may cause these side effects:

  • Dry mouth

  • Mouth and gum sores

  • Difficulty swallowing

  • Stiffness in the jaw

  • Nausea

  • Hair loss

  • 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 these side effects:

  • Difficulty swallowing

  • Shortness of breath

  • Breast or nipple soreness

  • Shoulder stiffness

  • Cough, fever, and fullness of the chest, known as radiation pneumonitis. This happens between 2 weeks and 6 months after radiation therapy.

  • Radiation fibrosis, which causes permanent lung scars from untreated radiation pneumonitis. The radiation oncologist knows how to lower the risk of fibrosis.

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

  • Nausea and vomiting

  • Diarrhea

These symptoms will likely disappear after treatment. And your doctor can prescribe drugs to manage these side effects. Making changes to your diet may also reduce your discomfort.

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

  • Diarrhea

  • Rectal bleeding

  • Incontinence, which is when a person is not able to control his or her bladder

  • Bladder irritation

Additionally, men and woman may have different symptoms.

Potential side effects for men include:

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

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

For women:

  • Changes in menstruation, such as having menstruation stop

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

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

Radiation recall

Radiation recall is a rash that looks like a severe sunburn. It is rare and happens when certain types of chemotherapy are given during or soon after external beam radiation therapy.

The rash appears on the part of the body that received radiation. Symptoms may include redness, tenderness, swelling, wet sores, and peeling skin.

Typically, these side effects start within days or weeks of radiation therapy. But they can also appear months or years later. Doctors treat radiation recall with medications called corticosteroids. Rarely, you may wait until the skin heals before continuing chemotherapy.

Coping with side effects

Everyone’s experience with cancer treatment is different. Before treatment, ask your health care team which side effects you may develop.

And continue talking with the team throughout your treatment schedule. Communicate when side effects appear or worsen. That will allow your health care team to provide treatment options.

Related Resources

What to Expect When Having Radiation Therapy

Fear of Treatment-Related Side Effects

Proton Therapy

More Information

National Cancer Institute: Radiation Therapy Side Effects

ASCO answers; Radiation TherapyDownload ASCO's free Radiation Therapy fact sheet. This 1-page printable PDF gives an introduction to radiation therapy, including an overview of the different types of radiation, what to expect during treatment, possible side effects, terms to know, and questions to ask the health care team. Order printed copies of this fact sheet from the ASCO Store.