Detecting HNPCC

Last Modified: April 18, 2003


Dear OncoLink "Ask The Experts,"
My family history involves non-polyp colon cancer: How is this type of cancer detected before it is too late if there are no polyps evident? My father had a "clean" colonoscopy 2 years prior to his diagnosis with terminal colon cancer (age 52). His father and 4 of his siblings along with their mother all died of the same disease. I have just had my first colonoscopy at age 36.  


Timothy C. Hoops, MD, Clinical Assistant Professor of Medicine in the Gastroenterology Division at the University of Pennsylvania and Director of Gastroenterology at Penn Medicine at Radnor, responds:

Generally we feel that most, if not all, cancers begin as polyps. The biology of these cancers suggests a multistep process that includes the adenomatous polyp as a precursor. Theoretically, it would be possible for a cancer to develop directly, but I doubt that. Rather, the explanation may be that a polyp was missed during a colonoscopy (we know that can happen, especially with very small or flat polyps), or that the process of developing a polyp and cancer occurred in an accelerated manner. It has been well described in the medical literature that patients can have normal colonoscopies and in 1 to 3 years a cancer is found. Most commonly this occurs in the familial syndrome HNPCC. With your family history, I think you are at risk for this disease. In these situations, I generally will recommend colonoscopies at a minimum of every two years and often every year. Genetic testing of your family might determine whether they carry a mutation causing HNPCC. If one is found, you could then be tested; if you carry the gene, you need intensive surveillance. If you don't carry the gene, you then would not be at increased risk and could revert to a standard screening program.

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