Radiation Therapy Principles

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Side effects of radiation to specific areas


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 troublesome.

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, and can cause symptoms like seizures, mental status changes, headaches, trouble speaking or walking, and other changes. It can be hard to tell if these symptoms are from necrosis or from the tumor coming back. Imaging tests like MRI or PET scans can help, but biopsy may be needed to be sure. Patients with radiation necrosis usually do better than patients whose brain tumors come back. But still, a number of patients with radiation necrosis do poorly or even die.


When radiation treatments include the chest, it can affect the lungs. 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 a cough. These symptoms are sometimes treated with steroids. Depending on the location of the area getting radiation, some people also have trouble swallowing.

Radiation pneumonitis occurs in about 5 to 20% of people get radiation therapy for lung cancer. It can also be caused by radiation to the chest for breast cancer, lymphomas, or other cancers. This inflammation may occur from about 6 weeks to 6 months after completing external radiation therapy. Common symptoms include shortness of breath, chest pain, cough, and fever. Radiation pneumonitis is treated by trying to decrease the inflammation. Steroids, like prednisone, are usually used.

Another possible effect radiation can have on the lungs is fibrosis (stiffening or scarring). This means the lungs are less able to expand and take in air. Fibrosis can cause shortness of breath and make it hard to exercise. This problem may show up months or even years after treatment.

Digestive tract

Radiation to the chest and abdomen (belly) may cause swelling and inflammation in the esophagus (the tube connecting the throat to the stomach), stomach, or intestine (bowels). 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’s severe, some patients may need intravenous (IV) fluids to avoid or treat dehydration and strong medicines like morphine to treat pain. Diarrhea also can be treated with medicines and may be helped by avoiding spicy, fried, or high fiber foods.

Digestive problems usually go away within a week or 2 of the last radiation treatment. Rarely they can be serious enough to cause long-term problems – such as scarring that can cause permanent narrowing of the esophagus, or ulcers that can cause abnormal openings in the intestine. Diarrhea and bleeding can result if the colon or rectum is affected (colitis or proctitis).

Reproductive/sex organs

Fertility in men: 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 called a clam shell.

See our document called Fertility and Men With Cancer to learn more about preserving fertility in men.

Fertility in women: It’s harder to protect the ovaries when women are 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.

See our document called Fertility and Women With Cancer to learn more about preserving fertility in women.

Sexual effects of radiation therapy on women: Radiation to the pelvic area can make the vagina tender and inflamed during and for a few weeks after treatment. The area may scar as it heals. This scarring can interfere with the vagina’s ability to stretch. The lining of the vagina also gets thinner, and might bleed slightly after sex. A few women get ulcers, or sore spots, in their vaginas. It may take many months for these areas to heal after radiation therapy ends.

The scarring that normally occurs after pelvic radiation can also shorten or narrow the vagina so much that a woman might not be able to have sex or get a Pap smear 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 sex that includes vaginal penetration 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, it helps allow 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 any of these areas are being radiated, sex may be uncomfortable because of sore spots or inflamed tissues in the vulva or vagina. Other side effects of radiation can also make a person less interested in sex during treatment. Women should discuss these issues with their doctors. If you have sexual problems during or after radiation, talk with your doctor or nurse. You can read more about this in our booklet, Sexuality for the Woman With Cancer.

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

About 1 man in 3 who gets radiation in the pelvic area will notice a change in his ability to have erections. This change most often develops slowly over the first couple of years 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 of having 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. Testosterone levels usually return to normal within 6 months of radiation therapy. But if a man has problems with low sexual 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 raise low levels 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 called Sexuality for the Man With Cancer.

Last Medical Review: 10/23/2013
Last Revised: 10/23/2013