Hereditary Non-Polyposis Colorectal Cancer (HNPCC)

My dad died of colon cancer; so did his mother. My uncle got it when he was 48. My sister has ovarian cancer. I'm 44, my son is twelve, and my daughter is seven--of course I wonder if I'm next, but I worry the most about their future.

The most common form of inherited colon cancer--hereditary nonpolyposis colorectal cancer, or HNPCC--may be responsible for one in six colon cancers. Over a million Americans may carry one of four mutated genes known to be involved in HNPCC. People with a defective gene face about an 80 percent chance of developing colon cancer, usually before age 50. HNPCC carriers also have higher risks for stomach and kidney cancers, and women have higher risks for ovarian and uterine cancers. An NCI researcher wrote:

Since 1913, scientists have suspected a genetic connection in families with an unusually high incidence of cancer. In 1993 scientists discovered that the responsible mutation for certain colorectal cancers occurs in a gene critical for repairing damaged DNA. The function of this gene was first determined in studies of bacteria and yeast. Only recently have researchers had the tools to move from observations to the unequivocal identification of culprit genes. Now we have the knowledge and the tools to move toward repairing or circumventing the defect. This was science fiction only 10 years ago. The pace of discovery will accelerate from now on.

In HNPCC, the gene mutations cause a breakdown in the system that corrects DNA duplication errors during cell division. Over time, uncorrected errors in other key genes allow cancers to develop at an accelerated pace. This is a primary cause of cancer--a pathway that enables a cell to evolve quickly from a normal cell to a cancerous one. HNPCC cancer cells also seem able to resist normal signals to stop dividing or die. The same problems have been found in cancers that do not appear to be inherited, which means that knowledge gained from HNPCC research may be relevant to many other cancers.

Now we need to focus on the biological basis of these genetic changes and learn how interactions with other genes and with environmental factors influence which HNPCC gene carriers develop cancer. Then we can find ways to keep those at high risk from developing malignancies. We have to learn how best to screen and counsel people about their cancer risk, and we must address the important medical, social, ethical, and legal issues that come with genetic knowledge.

I will be tested. I'll let my children decide for themselves when they are older. We are doing what we can to minimize the risk by eating a high-fiber, low-fat diet. I'm very encouraged by the research. By the time my kids might get cancer, I think they'll know how to reverse the effects of these faulty genes. I want this sword lifted from over my family's head.

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