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Potential side effects of radiation therapy for small intestine cancer

Side effects can occur with any type of treatment for small intestine cancer, but not everyone has them or experiences them in the same way. Side effects of radiation therapy will depend mainly on the:

  • size of the area being treated
  • specific area or organs being treated
  • total dose
  • treatment schedule

Radiation therapy damages cancer cells, but healthy cells in the treatment area can also be damaged, even though steps are taken to protect them as much as possible. Different cells and tissues in the body tolerate radiation differently.

Side effects can happen any time during radiation therapy. Some may happen during, immediately after or a few days or weeks after radiation therapy. Most side effects go away after radiation therapy is completed. Late side effects can occur months or years after radiation therapy. Some side effects may last a long time or be permanent.

It is important to report side effects to the healthcare team. Many side effects can be relieved by medications, a change in diet or other measures. Doctors may also grade (measure) how severe certain side effects are. Sometimes radiation therapy treatments need to be adjusted if side effects are severe.


Fatigue is one of the most common side effects of radiation therapy. Fatigue may be caused by anemiaanemiaA reduction in the number of healthy red blood cells., poor appetite or depression. It may also be related to toxic substances that are produced when cancer cells break down and die.

Fatigue usually occurs during the second week of radiation treatment or later. Symptoms of fatigue may increase or become more severe over the course of treatment. Fatigue usually goes away gradually after treatment has ended, but some people continue to feel tired for several weeks or months after radiation therapy.

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Skin reactions

Skin reactions occur because external beam radiation travels through the skin to reach the area being targeted for treatment. The skin in the radiated area may become red, dry or change colour (become darker or tanned looking). Most skin reactions occur within the first 2 weeks of receiving radiation treatment and these are usually mild with treatment for small intestine cancer. They usually go away a few weeks after treatment. Some skin changes, like skin darkening or scarring, can persist. Some people do not experience any skin reactions with radiation therapy.

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Nausea and vomiting

Nausea and vomiting is not a common problem with radiation therapy, but can occur depending on the area being treated. People receiving radiation to the stomach and upper abdomen are more likely to have nausea and vomiting. Nausea and vomiting occur a few hours after radiation treatment.

Nausea and vomiting should be reported to the radiation therapy team. It may help to have a small snack or not eat for a few hours before treatment, or to wait a few hours after treatment before eating again.

Nausea and vomiting can usually be managed with anti-nausea medicine and usually go away after treatment is finished.

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Diarrhea is frequent and very loose (watery) stools. Abdominal cramping may occur with the diarrhea. Diarrhea often begins 2–3 weeks into radiation therapy. Diarrhea usually goes away once radiation therapy treatments are completed.

Report diarrhea to the radiation therapy team. They may recommend a change in diet and can suggest over-the-counter or prescription medicines to help relieve diarrhea.

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Radiation enteritis

Radiation enteritis is irritation of the small and large intestine that occurs during or after radiation therapy to the abdomen, rectum or pelvis. The intestine is very sensitive to the effects of radiation and larger doses of radiation are sometimes needed to treat tumours in the abdomen or pelvis. The intestine in the radiated area becomes inflamed and causes nausea, vomiting, abdominal cramping and diarrhea. It can occur when radiation therapy is first given and up to 8 weeks after a radiation treatment (called acute radiation enteritis). A small percentage of people will develop a long-term problem called chronic radiation enteritis.

Report cramping and diarrhea to the radiation therapy team. They can suggest over-the-counter medicines or may prescribe medications to help relieve diarrhea.

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