Small-Intestine Cancer: Patient Guide

The small intestine is the longest stretch of the digestive tract, yet cancer starts there far less often than in the colon. The American Cancer Society projects 14,450 new cases in the United States in 2026, and 2,170 deaths. That is 0.7 percent of all new cancer diagnoses.

Two facts shape everything else. The organ is long and folded, so it is hard to see. And the disease is uncommon enough that many general surgeons and oncologists see only a handful of cases.

Incidence is climbing. Age-adjusted rates rose an average of 2.3 percent per year over 2014 to 2023. The rate of new cases was 2.7 per 100,000 people per year for 2019 to 2023, and the median age at diagnosis was 66.

The first thing to get from your pathology report is the cell type, because the diseases behave differently and are treated differently.

• Adenocarcinoma. The most common. NCI puts it at roughly 25 to 50 percent of primary malignant tumors of the small intestine. Most occur in the duodenum, the first segment just past the stomach.
• Neuroendocrine tumors. About 20 percent of malignant lesions here. They occur more often in the ileum, the last segment, than in the duodenum or jejunum.
• Lymphoma. Uncommon, and of the non-Hodgkin type.
• Sarcoma. Leiomyosarcoma is the most common one, and it turns up most often in the ileum.
• Gastrointestinal stromal tumors, usually called GISTs.

If your report says neuroendocrine tumor or GIST, most of what follows about adenocarcinoma staging and chemotherapy does not apply to you. Ask which disease you actually have before reading further about treatment.

NCI lists these risk factors for small intestine cancer:

• Eating a high-fat diet.
• Having Crohn disease.
• Having celiac disease.
• Having familial adenomatous polyposis, known as FAP, an inherited condition that causes many polyps in the colon.

Two of those matter for surveillance. If you have Crohn disease or FAP, tell any new gastroenterologist. Long-standing abdominal symptoms in someone with Crohn disease are easy to attribute to the Crohn disease itself.

The symptoms NCI lists are ones most people would sit on for months:

• Pain or cramps in the middle of the abdomen.
• Weight loss with no known reason.
• A lump in the abdomen.
• Blood in the stool.

None of those point clearly at the small bowel. Iron-deficiency anemia with no obvious cause is another common route in, because slow bleeding from a small bowel tumor shows up in blood counts before it shows up in the toilet.

A standard upper endoscopy sees the esophagus, stomach, and duodenum. A colonoscopy sees the colon and the very end of the ileum. Between them lies a long stretch that neither reaches, which is why the tests below exist.

• Capsule endoscopy. You swallow a capsule containing a light and a tiny wireless camera, which photographs the bowel as it passes.
• Double balloon endoscopy. Two tubes, one inside the other, with inflatable balloons that pleat the bowel over the scope so it can be advanced much further.
• CT and MRI, for cross-sectional pictures of the tumor and any spread.
• Upper GI series with small bowel follow-through, which uses barium as a contrast agent.
• Biopsy, and sometimes laparotomy, meaning an operation to look inside the abdomen directly.

One practical point about capsule endoscopy: it takes pictures but cannot take tissue. If it finds something, a scope or an operation still has to reach it.

For adenocarcinoma, staging uses the AJCC TNM system. T describes how deep the tumor has grown through the bowel wall:

• T1a: invades the lamina propria, the layer just under the surface lining.
• T1b: invades the submucosa, the layer beneath that.
• T2: invades the muscularis propria, the muscle layer.
• T3: grows through the muscle layer into the subserosa or nearby perimuscular tissue.
• T4: perforates the visceral peritoneum, the membrane covering the bowel, or invades other organs or structures.

N counts involved lymph nodes, and the cut point is three:

• N1: cancer in one or two regional lymph nodes.
• N2: cancer in three or more regional lymph nodes.

M1 means distant spread. The stage groupings follow directly:

• Stage 0: Tis, N0, M0.
• Stage I: T1 or T2, N0, M0.
• Stage IIA: T3, N0, M0.
• Stage IIB: T4, N0, M0.
• Stage IIIA: any T, N1, M0.
• Stage IIIB: any T, N2, M0.
• Stage IV: any T, any N, M1.

Notice that any positive node makes it stage III regardless of depth. This is why the number of nodes the surgeon removes and the pathologist examines matters. Ask for that count.

Surgery is the core. NCI describes resection, meaning removal of the affected segment of bowel along with nearby tissue. When the tumor cannot be removed, a bypass may be done to route food around a blockage and relieve symptoms.

Radiation and chemotherapy are used after surgery as adjuvant treatment, or on their own for symptom control. Immunotherapy and radiosensitizers, drugs that make tumors more responsive to radiation, are being tested in clinical trials.

Because duodenal tumors sit near the pancreas and bile duct, removing them can require a larger operation than people expect. Ask what specific operation is planned and what it removes.

SEER reports a 5-year relative survival of about 71.8 percent overall for small intestine cancer, based on people diagnosed between 2016 and 2022, with a clear gradient by extent of disease:

• Localized: 86.3 percent.
• Regional: 79.6 percent.
• Distant: 47.9 percent.

These pool every cell type together, including neuroendocrine tumors, which generally behave less aggressively than adenocarcinoma. Your own numbers depend on cell type as much as stage.

• You are vomiting repeatedly and passing no gas or stool, which can mean bowel obstruction.
• Your abdomen becomes swollen, hard, and severely painful.
• You vomit blood, or pass black tarry stools.
• You have a fever with severe abdominal pain.

• Which cell type is this, and does that change the whole plan?
• Which segment is it in: duodenum, jejunum, or ileum?
• How many lymph nodes were removed, and how many contained cancer?
• Should I be tested for Lynch syndrome or FAP, and should my relatives be?
• Is there a clinical trial for this specific cell type?
• How many of these operations does this surgeon do in a year?

https://www.cancer.gov/types/small-intestine/hp/small-intestine-treatment-pdq

https://www.cancer.gov/types/small-intestine/patient/small-intestine-treatment-pdq

https://seer.cancer.gov/statfacts/html/smint.html