Genetic ties found in colon cancer cases


With newer and improved tools in the field of genetics, our awareness has risen that approximately 10 percent of colon cancers have strong genetic roots. In other words, patients are carrying genes inherited from their parents predisposing them to develop colon cancer at an earlier age.

As a rule of thumb, the older patients are with cancer at presentation, the more environmental factors play a role. The younger they are, the more genetic factors (damaged chromosomes inherited by one or two family members) are responsible.

While we physicians can test individuals for genetic defects, there is still a heavy emphasis on detailed family histories, enabling the potential for earlier screening tests or ordering genetic tests. We know it takes approximately 10 years from the earliest cell change to a full-blown cancer.

Molecular genetics allows us to obtain blood test for changes in the chromosomes.

The two forms with which we are most concerned are a) Polyposis coli and b) Hereditary non-polyposis coli ("Lynch syndrome").

Polyposis coli patients develop hundreds of growths in the colon by the time they reach their 20s and invariably will suffer from colon cancer when they are 40. Only the removal of the entire colon will save these patients from their doomed fate. It is also important to stress that these individuals can also form cancers in other areas, such as the reproductive organs and the small bowel, and will need lifelong checkup programs.

Lynch syndrome is much more common and typically family members present with colon cancers in their 40s and 50s, often in the right side. Classically, first-degree relatives must be involved with two or more affected generations.

A ground breaking scientific discovery revealed that each and every cancer goes through multiple steps of transformation from an innocent, tiny polyp to a full-blown tumor. Only the removal at an early phase of this process can diminish one's chance of dying from colon cancer.

Everyone should start colon cancer screening at age 50 unless there is evidence of family history of the disease in which case testing should be undertaken 10 years earlier than the youngest family member was when affected.

The future holds great promises and will invariably introduce discoveries from our basic science into clinical practice. It may mean that we test stool samples for genetic mutations, obtain blood tests to determine one's individual risk and come up with a personalized way to prevent cancers.

Meanwhile, we use a carefully obtained family history to counsel our patients and our most powerful tool -- the colonoscope to remove precursors of colorectal cancer.

Dr. Harald Schoeppner is a gastroenterologist at Providence St. Mary Medical Center. This is the first in a series of four Thursday columns this month on colon health.


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