Johns Hopkins Professor Frank Giardiello, M.D., Professor explains why knowing your family tree can save your life.
Following the publication of the complete sequence of the human genome in 2003, researchers announced that much of this information had been placed on a single, dime-sized glass slide called a DNA microarray or gene chip. This tool allows researchers to rapidly examine humankind’s estimated 35,000 genes so they can pinpoint those linked to disease, an achievement that promises to transform the practice of medicine in the near future.
One day gene chips may be used to generate individual genetic profiles that can quickly predict a person’s risk of many common and potentially deadly medical problems, including breast cancer, colon cancer, diabetes, heart disease, and stroke. These high-tech devices may begin to appear in your doctor’s office within the next decade or so.
In the meantime, you can harness the genetic information locked in your genes with one of the most basic and effective tools known to medicine: a detailed and accurate family history. By learning as much as you can about your own family’s health history, you can open a window on your genetic inheritance and better assess your risk of certain diseases. Armed with this information, you can step up efforts to prevent a particular disease or detect it at an early stage, when therapy is likely to be most effective.
If your family history indicates an unusually high risk of a particular condition, your doctor may suggest considering genetic testing. “Someone who has several family members, say parents or siblings, with colon cancer— and particularly if the colon cancer developed before age 50—should think about having genetic testing,” advises Frank Giardiello, M.D., Professor and Chief of Gastroenterology at Johns Hopkins.
Scientists have identified several genes that increase the risk of developing two types of hereditary colon cancer: familial adenomatous polyposis (FAP) and hereditary nonpolyposis colorectal cancer (HNPCC).
- People with FAP have hundreds, or even thousands, of polyps in the colon and nearly always develop colon cancer by age 40 unless their colon is surgically removed. Thus, they can benefit from aggressive monitoring and treatment.
- People who carry one or more of the gene mutations responsible for HNPCC have an 80% risk of developing colon cancer during their lifetime. Furthermore, women with this mutation also have a 40% to 60% lifetime risk of endometrial cancer and a 10% lifetime risk of ovarian cancer. Genetic testing for HNPCC can produce significant benefits by identifying candidates for more intensive screening since annual colonoscopy can greatly reduce the risk of dying of colon cancer. More aggressive monitoring and, perhaps, prophylactic surgery could also reduce mortality from endometrial and ovarian cancer associated with HNPCC mutations.
Because a gene mutation for colon cancer occurs more frequently in people of Ashkenazi Jewish ancestry than in the general population, genetic testing for hereditary colon cancer might also be recommended for people with this ethnic background if they have multiple colon polyps or a family history of colon cancer.
For more Alerts and Special Reports, please visit the Colon Cancer Topic page.
