Small intestine cancer starts when cells in the small intestine start to grow out of control. The small intestine is the largest part of the gastrointestinal tract (GI tract), which processes food for energy and rids the body of solid waste. The small intestine is not as common as other cancers of the GI tract such as colon, rectal, stomach, and esophageal cancers in the United States. They account for fewer than 1 in 10 cancers in the GI tract, and fewer than 1 in 100 cancers overall. (American Cancer Society, 2023)
Small intestine cancer can be subdivided into duodenal cancer (the first part of the small intestine) and cancer of the jejunum and ileum (the latter two parts of the small intestine). Duodenal cancer has more in common with stomach cancer, while cancer of the jejunum and ileum have more in common with colorectal cancer. Five-year survival rates are 65%.[1]
Experts believe that small intestine cancer develops much like colorectal cancer. It first begins as a small growth on the inner lining of the intestine (polyp), which over time becomes cancer. (American Cancer Society, 2023)
Approximately 50% of adenomas of the small intestine arise in the duodenum even though this location comprises only 4% of the length of the small intestine. These adenomas occur mainly close to the ampulla of Vater, the outlet of the common bile duct from which bile acids are released.[2] This area is also closely associated with the pancreas, so they are treated as pancreatic cancer.
The small intestine works by mixing food and gastric juices into a thick fluid in the stomach and then emptied into the small intestine. It then continues to break down and absorb the nutrients. Although it is referred to as the small intestine, it is the longest section of the GI tract being approximately 20 feet long. The length of the small intestine comprises 75% of the length of the entire gastrointestinal tract[3]
There are three parts of the small intestine. The duodenum is the 1st section of small intestine and only about a foot long. The jejunum and ileum make up most of the small intestine. Most of the nutrients in food are absorbed into the bloodstream in these two parts. (American Cancer Society, 2023)
Relative incidence of histopathologic types of small intestine cancers, and their prognoses.[4]
Subtypes of small intestine cancer include:
Adenocarcinoma-This cancer begins in the gland cells that line the inside of the intestine. Adenocarcinomas account for about 1 in 3 small intestine cancers.
Carcinoid tumors of the midgut-This is a type of neuroendocrine tumor (NET). They tend to be slow growing and are the most common type of small intestine tumor. (American Cancer Society, 2023)
Most small intestine cancers (especially adenocarcinomas) develop in the duodenum. Cancers developed in the duodenum are often found at the ampulla of Vater. (American Cancer Society, 2023)
Risk factors for small intestine cancer include:[5][6]
Age: Cancer risk increases with age. The average age diagnosis is 65.(Cleveland Clinic, 2022)
Race: In the U.S., small intestine cancer is slightly more common among people who identify as African Americans. Although lymphoma is more common among people who identify as white.(Cleveland Clinic, 2022)
HIV/AIDS- treatments like radiation therapy may weaken your immune system and make you more susceptible to small intestine cancer. Drugs that suppress your immune system may also increase your risk.(Cleveland Clinic, 2022)
Sex: Males are 25% more likely to develop the disease.(Cleveland Clinic, 2022)
Diet: Various research has suggested that diets high in red meat and salted or smoked foods may raise the risk of small intestine cancer.(Cleveland Clinic, 2022). A human prospective study observed a markedly elevated risk for carcinoid tumors of the small intestine associated with dietary intake of saturated fat[7]
Cholecystectomy, which alters the flow of bile to the small intestine, increases the risk of small intestinal adenocarcinomas,[8] and this risk declines with increasing distance from the common bile duct.
^Ross RK, Hartnett NM, Bernstein L, Henderson BE. Epidemiology of adenocarcinomas of the small intestine: is bile a small bowel carcinogen. Br J Cancer 1991;63:143–5
^Maguire A, Sheahan K. Primary small bowel adenomas and adenocarcinomas-recent advances. Virchows Arch 2018;473:265–73
^Delaunoit T, Neczyporenko F, Limburg PJ, Erlichman C (March 2005). "Pathogenesis and risk factors of small bowel adenocarcinoma: a colorectal cancer sibling?". Am. J. Gastroenterol. 100 (3): 703–10. PMID15743371.
^Cross AJ, Leitzmann MF, Subar AF, Thompson FE, Hollenbeck AR, Schatzkin A. A prospective study of meat and fat intake in relation to small intestinal cancer. Cancer Res 2008;68:9274–9
^Lagergren J, Ye W, Ekbom A. Intestinal cancer after cholecystectomy:
is bile involved in carcinogenesis. Gastroenterology 2001;121:542–7
American Cancer Society. (2023). Key statistics for small intestine cancer. American Cancer Society. Retrieved April 3, 2023, from https://www.cancer.org/cancer/small-intestine-cancer/about/what-is-key-statistics.html
Cleveland Clinic. (2022). Small intestine cancer: Symptoms, causes, Prognosis & Treatment. Cleveland Clinic. Retrieved April 4, 2023, from https://my.clevelandclinic.org/health/articles/6225-small-intestine-cancer
Markman, M. (2022, July 20). Intestinal cancer: Causes, symptoms & treatments. Cancer Treatment Centers of America. Retrieved April 4, 2023, from https://www.cancercenter.com/cancer-types/intestinal-cancer
Radhakrishnan, R. (2021, May 6). Is small intestine cancer curable? MedicineNet. Retrieved April 4, 2023, from https://www.medicinenet.com/is_small_intestine_cancer_curable/article.htm
