The frequency of hereditary large bowel cancer

In brief, an unknown but small fraction of colorectal cancer in the United States is due to single gene traits that are usually easy to identify by the clinician who is aware of the many disorders which predispose to colorectal cancer. An additional, perhaps a larger fraction could be attributed to familial cancer syndromes which may arise from environmental or genetic factors or both. In any case, once a familial or mendelian trait is recognized, the risk to offspring and sibs tends to be 50%, since most predisposing traits behave in an autosomal dominant fashion. Easy means of surveillance and surgical prophylaxis are at hand. The largest hurdle, in my opinion, is to prod the health care system into thinking of and acting on the family history and to overcome the misconception that genetic disease is untreatable and unpreventable. Indeed, given poor control of the best known environmental carcinogens (sunlight and tobacco use), heritable colorectal cancer may well be the most manageable determinant of colorectal cancer--much more so, perhaps, than environmental factors like diet.