Small Intestine Cancer, from the CureRays guide library.

Small intestine cancer is an uncommon tumor of the long middle section of the gut; surgery is the main treatment, with chemotherapy and focused radiation in supporting roles.

What it is.

Small intestine cancer is an uncommon cancer that begins in the small bowel — the long, coiled tube between the stomach and the colon where most of the body's food is digested and absorbed. Even though the small intestine makes up most of the length of the digestive tract, cancer there is rare compared with the stomach or colon, partly because food moves through it quickly and its lining renews itself often. Several different cancers can arise here, and they behave differently from one another, so identifying the exact type is an important first step. Because symptoms — like belly pain, cramping, anemia, or a blockage — can be vague and come on slowly, small intestine cancer is sometimes found later than other gut cancers. Treatment is tailored to the specific type, with surgery as the backbone for cancers that can be removed.

How radiation treats it.

Radiation uses focused high-energy x-rays to damage the DNA inside tumor cells so they can no longer grow and divide. The small intestine itself is sensitive to radiation and is always moving, so it has historically not been the main treatment for small bowel cancer. But modern, image-guided techniques make it possible to concentrate a precise dose on a fixed target — such as a tumor in the duodenum or a deposit in the liver — while protecting the rest of the gut. In small intestine cancer, radiation is used selectively: to help treat tumors that are hard to remove, to relieve bleeding, pain, or blockage, and to control specific spots that have spread. Treatments are painless and brief, given over a small number of sessions. Side effects depend on the area treated and are usually temporary, such as fatigue, nausea, or loose stools. Radiation works best here as a precise, supportive tool alongside surgery and medicine.

The ways we can treat it.

Targeted external-beam radiation. Precise radiation, sometimes combined with chemotherapy, can treat tumors in the duodenum that are difficult to remove surgically, or shrink them before an operation.

Palliative radiation. Focused radiation aimed at a bleeding or obstructing tumor, or a painful deposit, to relieve symptoms and improve comfort when surgery isn't the right option.

Stereotactic body radiation (SBRT). Highly precise, high-dose radiation in a few sessions can control a limited number of metastatic spots, such as in the liver, while sparing the surrounding bowel.

Questions we hear often.

Why is small intestine cancer so uncommon? The small intestine makes up most of the digestive tract's length, yet cancer there is rare. Doctors believe this is partly because food passes through quickly, the lining renews itself frequently, and the contents are more liquid and less irritating than in the colon.

Is small intestine cancer the same as colon cancer? Not exactly. The most common type, adenocarcinoma, is similar to colon cancer and treated in comparable ways, but the small intestine can also develop other cancers — neuroendocrine tumors, lymphoma, and GIST — each with its own treatment. Identifying the exact type guides care.

Will I need radiation? Often not. Surgery and, when needed, chemotherapy are the mainstays. Radiation is used selectively — for example, to treat a duodenal tumor that's hard to remove, to relieve bleeding or pain, or to control a deposit that has spread. Your team will tell you whether it fits your case.

This guide is informational only. It is not medical advice — please confirm anything here with your care team.