Normal body tissues vary in their response to radiation. As with tumors, normal tissues in which cells are quickly dividing may be affected. This causes some of the side effects of radiation treatment. Since radiation is a local treatment, many side effects depend on the area of the body being treated. The early effects of radiation may be seen a few days or weeks after treatments have started and may go on for several weeks after treatments have ended. Other effects may not show up until months, or even years, later. The major side effects are discussed below. Please see our document, Understanding Radiation Therapy: A Guide for Patients and Families for more ideas on dealing with side effects.

Fatigue

Fatigue is extreme tiredness that does not get better with rest. It is a common effect of radiation, but the exact cause is unknown. Sometimes tumors cause the immune system to make substances that lead to fatigue. Fatigue may also be caused by anemia (a low red blood cell count), poor nutrition, pain, medicines such as steroids or chemotherapy, depression, and stress.

There is no single treatment for fatigue, but if a cause can be found it should be treated. For example, if the fatigue is in part caused by anemia, some patients may benefit from blood transfusions or from medicines that cause the body to make more red blood cells.

Fatigue can last for a long time after treatment is over and some people never have as much energy as they did before treatment. Light or moderate exercise with frequent rest breaks may help to reduce fatigue. Talk with your doctor about this and other treatments that may work for you.

Skin changes

Radiation therapy today causes less skin damage than it did in the past because most of the radiation dose is delivered below the surface of the skin. You may still find that your skin shows a response to treatments. During the first 2 weeks of treatment, you may notice a faint redness. Your skin may become tender or sensitive. Dryness and peeling of the skin may occur in 3 to 4 weeks. After that, the skin over the treatment area may become darker. This is because of the effect radiation has on the cells in the skin that produce pigment (color). You also may have hair loss in the skin over the area that is being treated.

The skin may also become dry and itchy. Moisturizing the skin with aloe vera, lanolin, or vitamin E may help. Before using any skin products during treatment, ask the radiation doctor or nurse if it is OK. Some lotions that are fine to use after treatment is finished can actually make things worse during therapy. Avoid perfumes, deodorants, and skin lotions that contain alcohol or perfume. Also avoid powders unless approved by your doctor or nurse. Stay out of the sun as much as you can. If you must be outdoors, wear a hat and clothes that will protect your skin. After about a month of treatment, some people getting radiation may notice skin peeling and moist (weeping) areas. Let your medical care team know if this happens to you.

Later effects of radiation may include thinning of the skin. The skin may feel hard, especially if surgery has also been done in the same area. Some people may have trouble with wound healing in the area that was treated.

Mouth and throat problems

Mucositis (inflammation inside the mouth) is a short-term side effect that may happen when radiation is given to the head and neck area. It usually gets better within a few weeks after treatments are completed. Dry mouth and a loss of taste can be caused by radiation damage to the salivary glands and taste buds. Thick, rope-like saliva and swallowing problems may develop, too. These side effects often go away after treatments are finished, but in some cases may be permanent.

Keeping the mouth clean is important to lower the risk of infection. If your mouth becomes sore, you may be given medicine to numb the mouth or help the pain. It is taken before meals and may make it easier to eat. Be sure to tell your doctor about any pain and whether the medicines to help it are working.

Good nutrition is important for people with cancer. If the pain and irritation make it hard to eat or swallow, you may need to have a feeding tube put into your stomach for a while so you can take in enough nourishment. Your health care team will help you develop a plan to manage your symptoms. For more suggestions, see our documents, Understanding Radiation Therapy: A Guide for Patients and Families, Caring for the Person with Cancer at Home: A Guide for Patients and Families, and Nutrition for the Person with Cancer: A Guide for Patients and Families. 

Radiation to the head and neck area can affect your teeth, too, and increase your chances of getting cavities. Mouth care to prevent problems will be an important part of your treatment. Before starting radiation therapy, talk to your dentist and have a complete check-up. Also ask your dentist to talk to your radiation oncologist before your radiation treatments begin. Any dental work that you need may have to be done before radiation begins and daily fluoride treatments may be prescribed to protect your teeth.

Side effects when certain areas are treated

Brain

Radiation therapy to large areas of the brain can sometimes cause changes in brain function that can lead to memory loss, lower sexual desire, or poor tolerance for cold weather. Nausea, unsteady walking, and changes in vision may also be noticed. Usually these symptoms are minor compared to those caused by a brain tumor, but they can be a bother.

Sometimes a large area of dead cells, called radiation necrosis, forms at the site of the radiation in the brain. This can happen months to years after radiation is given. Patients with radiation necrosis usually do better than patients whose brain tumors come back. But still, a small number of patients with radiation necrosis do poorly or even die.

Lung

When radiation treatments include the chest area, the lungs can be affected. One early change is a decrease in the levels of a substance, called surfactant, which helps keep the air passages open. Low surfactant levels keep the lungs from fully expanding. This may cause shortness of breath or cough. These symptoms are sometimes treated with steroids. Depending on the location of the radiation, some people also have trouble swallowing.

Another possible effect of radiation on the lungs is fibrosis (stiffening or scarring). This reduces the ability of the lungs to inflate and take in air. If a large area of the lungs is exposed to radiation, these changes can cause shortness of breath and less tolerance for physical exercise. This problem may show up months or years after treatment is completed.

Digestive tract

Radiation to the chest and abdomen (belly) may cause swelling and inflammation in the esophagus (swallowing tube), stomach, or intestine. This can cause pain, nausea, vomiting, or diarrhea. Antacids, sometimes combined with a numbing medicine such as lidocaine, may help relieve pain from an inflamed esophagus. Nausea and vomiting can also be treated with medicines. If it is severe, some patients may need intravenous fluids to avoid or treat dehydration. Diarrhea can be treated with medicines and may be helped by avoiding spicy, fried, or high fiber foods.

Reproductive/sex organs

Fertility: Radiation to the testicles can cause permanent loss of sperm production. Unless the cancer is in the testicles, they can usually be protected from radiation by using a shield that is known as a "clam shell."

It is harder to protect the ovaries in women getting radiation to the abdomen (belly). If both ovaries are exposed to radiation, early menopause and permanent infertility can result. Sparing one ovary can prevent these side effects. If the uterus (womb) is exposed, radiation can cause scarring and fibrosis. This can cause problems with normal expansion during a later pregnancy.

Sexual impact of radiation therapy in women: Radiation to the pelvic area can cause the vagina to be tender and inflamed during and for a few weeks after treatment. Scarring of the area may occur as it heals and can interfere with the ability of the vagina to stretch. The lining of the vagina also gets thinner, which may cause light bleeding after sex. A few women get ulcers, or sore spots, in their vaginas. It may take many months after the end of radiation therapy for these areas to heal.

The scarring that normally occurs after pelvic radiation could shorten or narrow the vagina so much that a woman may not be able to have sex without pain. This can often be prevented by stretching the walls of the vagina a few times a week. One way to do this is to have sexual intercourse at least 3 to 4 times a week. Another option is to use a vaginal dilator. A dilator is a plastic or rubber rod or tube used to stretch out the vagina. It feels much like putting in a large tampon for a few minutes. Even if a woman is not interested in staying sexually active, keeping her vagina normal in size allows her doctor to do pelvic exams. This is an important part of follow-up care after treatment. Doctors, nurses, and other health care team members can tell you more.

As long as a woman is not bleeding heavily from a tumor in her bladder, rectum, uterus, cervix, or vagina, she may be able to have sex during pelvic radiation therapy. The outer genitals and vagina are just as sensitive as usual. But if the vagina is being radiated, sex may be uncomfortable because of sore spots or inflamed tissues. Women should follow their doctors' guidelines about sex during radiation therapy. Talk with your doctor or nurse about any sexual problems you may have. You can read more about this in our booklet, Sexuality for the Woman with Cancer.

Sexual impact of radiation therapy in men: Radiation therapy to the pelvis can damage the arteries and nerves that supply the penis and cause problems with erections. The higher the dose of radiation and the wider the area of the pelvis that is treated, the greater the chance that an erection problem will develop.

About 1 in 3 men who get radiation in the pelvic area will notice a change in his ability to have erections. This change most often develops slowly over the first year or so after radiation treatment. Some men continue to have full erections but lose them before reaching climax. Others no longer get firm erections at all. Men who are older, who didn't have full erections before they were treated, who have high blood pressure, or who have been heavy smokers seem to have a higher risk for erection problems after radiation.

Testosterone is a male hormone that plays an important role in erections. Some men have less testosterone after pelvic radiation. The testicles, which make testosterone, may be affected either by a mild dose of scattered radiation or by the general stress of cancer treatment. The testosterone level will usually recover within 6 months of radiation therapy. But if a man notices erection problems or low desire after cancer treatment, the doctor may decide to do a blood test to find out if testosterone is low. Some men can take testosterone to get low levels back to normal. Men with prostate cancer should know that replacement testosterone can speed up the growth of prostate cancer cells. You can read more about sexual problems during cancer in our booklet, Sexuality for the Man with Cancer.

Go back to Radiation Principles.

Last Medical Review: 07/17/2009
Last Revised: 07/17/2009