Small Bowel Cancer: Scoping Out a Rarity

George Monemvasitis; Michael J. Overman, MD

Disclosures

January 09, 2015

Editor's Note: The rarity of small bowel cancer has hampered research efforts in uncovering associated molecular pathways and guiding optimal treatment strategies. There were an estimated 9160 new cases of small intestine cancer in the United States in 2014,[1] of which one third were adenocarcinomas.[2] In comparison, there were an estimated 96,830 new cases of colon cancer[1] a much larger incidence rate considering that the small bowel comprises 75% of the length and 90% of the surface area of the lower intestinal tract.[2]

In an interview with Medscape, Michael J. Overman, MD, an associate professor in the Department of Gastrointestinal Medical Oncology at the University of Texas MD Anderson Cancer Center in Houston, discusses the most common predisposing factors for small bowel adenocarcinoma; the importance of diagnosing unexplained iron deficiency anemia, especially coupled with abdominal pain or gastrointestinal bleeding; and ongoing trials that are evaluating new therapeutic options for this disease.

Medscape: What predisposing factors are associated with an increased risk for small bowel adenocarcinoma?

Michael J. Overman, MD: There are three big factors. The first is hereditary nonpolyposis colorectal cancer (HNPCC), or Lynch syndrome, which predisposes not only to colorectal cancer but also to a number of other cancers, including small bowel adenocarcinoma. The second is inflammatory bowel disease (IBD), particularly Crohn's disease; these patients can have involvement of the distal small bowel (ileal adenocarcinoma). Celiac disease would be the third factor. Celiac disease is a gluten-associated enteropathy in which you have an autoimmune attack against gluten in your diet. You'll have inflammation in the epithelial lining of your small bowel as your body reacts to the gluten in your diet, and that inflammation can lead to an increased risk for small bowel adenocarcinoma. Those are the big three predisposing factors. However, the majority of small bowel adenocarcinomas, approximately 70%, are sporadic and have unclear factors associated with them.

Medscape: Is any form of screening advisable for someone who has one or more of these predisposing factors?

Dr Overman: Screening poses several issues, given the rarity of the cancer and the challenges of imaging the small bowel. At present there are no cancer guidelines that recommend screening for small bowel adenocarcinoma. The screening modality would likely be a capsule endoscopy or enteroscopy, but these are invasive procedures for such a rare disease. For the general population, we don't have a screening test that is appropriate. For people with increased risk—the three categories I mentioned—we don't have good data, again because of the rarity of the disease. There are some data supporting screening in patients with Lynch syndrome, utilizing capsule endoscopy,[3] but screening this population is not recommended in current guidelines. The frequency of screening is also uncertain. One dataset mentions a one-time screening.[4] The majority of HNPCC patients, however, will not get small bowel adenocarcinoma. Also, screening patients with IBD could be challenging because the capsule can get stuck by strictures caused by the IBD. There's a higher risk for surgery to remove a stuck capsule [than for small bowel adenocarcinoma], so it is difficult to recommend screening in this group without good data. Overall, if you have a predisposing risk, you may want to have a discussion with your doctor.

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