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Radiation Therapy for Small Intestine Cancer (Adenocarcinoma)

(Note: This information is about small intestine cancers called adenocarcinomas. To learn about other types of cancer that can start in the small intestine, see Gastrointestinal Carcinoid Tumors, Gastrointestinal Stromal Tumors, or Non-Hodgkin Lymphoma.)

Radiation therapy uses high-energy radiation to kill cancer cells. It may be an option for those whose cancer cannot be removed completely with surgery and is causing problems such as pain or bleeding into the intestines.  Radiation might also be used after surgery to try to kill any remaining cancer cells (known as adjuvant therapy), although it’s not yet clear how helpful this is.

External-beam radiation therapy is the type of radiation used most often for small intestine cancer. For this treatment, radiation beams are aimed at the tumor from a machine outside the body.

Before treatment starts, the radiation team will take careful measurements to find the correct angles for aiming the radiation beams and the proper dose of radiation. This planning session, called simulation, usually includes getting imaging tests such as CT or MRI scans.

Radiation therapy is much like getting an x-ray, but the radiation is much stronger. The treatment itself is painless. It lasts only a few minutes, although the setup time – getting you into place for treatment – usually takes longer. You might get radiation treatment for several days in a row.

Possible side effects

The main side effects of radiation therapy to the intestines include:

  • Fatigue (tiredness)
  • Nausea and vomiting
  • Diarrhea
  • Skin changes in the area where the radiation beams passed through, which can range from mild redness to blistering and peeling

More information about radiation therapy

To learn more about how radiation is used to treat cancer, see Radiation Therapy.

To learn about some of the side effects listed here and how to manage them, see Managing Cancer-related Side Effects.

The American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as editors and translators with extensive experience in medical writing.

Chamberlain RS, Krishnaraj M, Shah SA. Chapter 54: Cancer of the Small Bowel. In: DeVita VT, Lawrence TS, Rosenberg SA, eds. DeVita, Hellman, and Rosenberg’s Cancer: Principles and Practice of Oncology. 10th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2015.

Cusack JC, Overman MJ. Treatment of small bowel neoplasms. UpToDate. Accessed at on January 18, 2018.

Doyon L, Greenstein A, Greenstein A. Chapter 76: Cancer of the Small Bowel. In: Niederhuber JE, Armitage JO, Doroshow JH, Kastan MB, Tepper JE, eds. Abeloff’s Clinical Oncology. 5th ed. Philadelphia, Pa: Elsevier; 2014.

National Cancer Institute. Physician Data Query (PDQ). Gastrointestinal Stromal Tumors Treatment. 2017. Accessed at on January 18, 2018.

Last Revised: February 8, 2018

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