Side Effects of Radiation Therapy

Approved by the Cancer.Net Editorial Board, 08/2020

Radiation therapy treats many types of cancer effectively. But like other cancer treatments, it often causes side effects. Each person experiences different side effects. Side effects depend on the type of cancer, its location, the radiation therapy dose, your general health, and other factors. It is important to talk with your health care team about any side effects you experience so they can find ways to help you.

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.

There have been major research advances in radiation therapy in recent years that have made it more precise. This has reduced this treatment's side effects, compared to radiation therapy techniques used in the past.

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. Or, they may last for several weeks after the final treatment. Some side effects may be long term. Talk with your treatment team about what to expect.

Are there options to prevent or treat these side effects?

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

Before treatment begins, ask what side effects are likely from the specific type of treatment you are receiving and when they may happen. And during and after treatment, let your health care team know how you are feeling on a regular basis.

What are common side effects of radiation therapy?

Radiation therapy is called a local treatment. This means that it only affects the area of the body that is targeted. For example, radiation therapy to the scalp may cause hair loss. But people who have radiation therapy to other parts of their body do not usually lose the hair on their head.

Common physical side effects of radiation therapy include:

Skin changes. 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 and other factors. Skin changes from radiation therapy usually go away a few weeks after treatment ends. If skin damage becomes a serious problem, your doctor may change your treatment plan. Lotion may help with skin changes, but be sure to check with your nurse or other health care team about which cream they recommend and when to apply it. It is also best to protect affected skin from the sun. Learn more about skin-related side effects.

Fatigue. Fatigue is a term used to describe feeling tired or exhausted almost all the time. Many patients experience fatigue. Your level of fatigue often depends on your treatment plan. For example, radiation therapy combined with chemotherapy may result in more fatigue. Learn 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 long-term or late effects. One possible late effect 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 first cancer.

What are site-specific side effects of radiation therapy?

Some side effects depend on the type and location of where radiation therapy is directed at on the body.

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 and managing eating challenges from head and neck treatments.

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:

  • Loss of appetite

  • Nausea and vomiting

  • Bowel cramping

  • Loose stool or diarrhea

These symptoms will likely go away after treatment. During treatment, your doctor can prescribe medicine to manage these side effects. Making changes to your diet may also reduce symptoms. It may be helpful to talk with an oncology dietitian.

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

  • Loose stool or diarrhea

  • Rectal bleeding

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

  • Bladder irritation

  • Sexual problems for men, 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 testicles (testes) or prostate gland. It can affect your ability to have children. Learn about ways to preserve fertility for men.

  • Changes in menstruation, such as having menstruation stop

  • Symptoms of menopause, such as vaginal itching, burning, dryness, and other changes to sexual health for women

  • If both ovaries receive radiation therapy, you may experience infertility. Learn about ways to preserve fertility for women.

What is 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, it may be necessary to wait until the skin heals before continuing chemotherapy.

Coping with side effects of radiation therapy

Everyone’s experience with radiation therapy is different. Side effects vary from person to person, even when given the same type of treatment. Before your treatment, ask your health care team which physical side effects are possible and what to watch for. There can also be emotional side effects, and seeking out mental health support to help with anxiety or stress is important.

Ask your health care team about ways to take care of yourself during the treatment period, including getting enough rest, eating well, and staying hydrated. Ask whether there are any restrictions on your regular exercise schedule or other physical activities.

And, continue talking with the team throughout your treatment. Always tell your health care team when side effects first appear, worsen, or continue despite treatment. That will allow your health care team to provide ways to help you feel better during and after treatment.

Questions to ask the health care team

  • What physical side effects are likely based on my specific radiation therapy treatment plan? When will they likely begin?

  • How can these side effects be prevented or managed?

  • How can I take care of the affected skin during my treatment period?

  • Who should I tell when a side effect appears or gets worse?

  • Are there specific side effects I should tell the doctor about right away?

  • Who can I talk with if I'm feeling anxious or upset about having this treatment?

  • If I'm having side effects that affect my nutrition, can you recommend an oncology dietitian?

  • What are other ways I can take care of myself during the treatment period?

  • Are there any restrictions on exercising or other physical activity during this treatment?

  • Could this treatment affect my sex life? If so, how and for how long?

  • Could this treatment affect my ability to become pregnant or have a child? If so, should I talk with a fertility specialist before cancer treatment begins?

  • What are the potential long-term effects of this type of radiation therapy?

  • If I'm worried about managing the financial costs of cancer care, who can help me?

  • Will special precautions be needed to protect my family and others from radiation exposure during my treatment period?

  • After radiation therapy is completed, what will my follow-up care plan be?

  • Why is follow-up care important for managing side effects of treatment?

Related Resources

Understanding Radiation Therapy

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.