Radiation
Radiation therapy uses targeted, high-dose X-rays or other high-energy rays to kill cancer cells. External radiation therapy comes from a machine outside the body. Internal radiation therapy involves inserting radioactive materials into the body near the cancer cells. Radiation can be used alone or before or after surgery and/or chemotherapy. The doctor may also give the patient drugs called radiosensitizers that make tumors more responsive to radiation therapy.

Side effects of radiation therapy can include a sun burnt-like patch of skin on the treated area, fatigue, diarrhea and vomiting.

Chemotherapy
Chemotherapy kills cancer cells with drugs that the patient takes orally or intravenously. Treatment of cancer of the small intestine is systemic, meaning the drug enters the bloodstream and kills cancer cells throughout the body. The patient may also be given chemotherapy following surgery to kill any cancer that was not removed. This is called adjuvant chemotherapy.

Side effects of chemotherapy include damage to normal cells, nausea and vomiting, a loss of appetite, hair loss and sores in the mouth or vagina.

Immunotherapy
Immunotherapy uses materials produced by the body or made in the laboratory to stimulate the immune system to fight cancer. Scientists are currently studying its effect on small intestine cancer. Immunotherapy is sometimes called biological therapy or biological response modifier (BRM) therapy.