Research > New Risk Assessment Model Estimates Probability of Inherited Colorectal Cancer in Patients
Volume 8 Number 1, Published 3-1-2002
Identifying hereditary colon cancer in
an individual or in a family can be life-saving. For patients with colorectal cancer who do not have any particular family history of the disease, the choice whether or not to undergo genetic testing to see if their disease
is hereditary may be problematic. For most, genetic testing isn’t warranted. Yet, half of those patients with the most common form of hereditary colorectal cancer may not have a family history of cancer and don’t know they are at risk.
An Accurate Predictor
Now, cancer researchers at Thomas Jefferson University Hospital have devised an approach they believe
will enable practicing clinicians to determine much more accurately
who is at risk for hereditary nonpolyposis colorectal cancer (HNPCC). HNPCC accounts for about 5 percent of colorectal cancers. This risk assessment approach also tells clinicians when it is appropriate to recommend that a patient has genetic testing for the HNPCC trait.
Researchers, led by Bruce M. Boman, MD, PhD, Director of the Division of Genetic and Preventive Medicine at Jefferson Medical College and Director of the Gastrointestinal Cancer Program at the Kimmel Cancer Center of Thomas Jefferson University, developed a model using the age
of an individual at diagnosis of colorectal cancer as the only criterion to determine his or her risk for HNPCC. Most develop the disease early, typically before age 55.
Dr. Boman presented his work October 4, 2000 at the annual meeting of the American Society of Human Genetics in Philadelphia.
“This is the first epidemiological model, as far as I know, proposed
to determine risk for hereditary colorectal cancer,” says Dr. Boman, who is a member of Jefferson’s Kimmel Cancer Center. “It’s simple. Those who develop HNPCC do
so at an early age. We simply took
the differential age distribution between colon cancer in HNPCC families versus colon cancer in the general population.”
According to the model, an individual with colorectal cancer diagnosed before age 35 and with an unknown family history would have a 77 percent chance of actually having HNPCC. For those under 65, the risk drops to 10 percent. According to statistical analysis, it turns out that genetic testing for HNPCC is most appropriate for all those patients diagnosed with colorectal cancer before age 55.
A Life-Saving Model
Dr. Boman believes the model will
be valuable for genetic counselors
in risk assessment of colorectal cancer patients. It will provide the percentage risk and will also provide a criterion for ordering genetic tests. “The model has the potential for saving lives because it allows us to find out who else in the family is at risk before that family member develops cancer.
“If the genetic tests show that there
is a trait for hereditary cancer in the individual, then the rest of the family would be tested,” he says. “If you detect a trait, you should screen other members in the family.”
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