Colorectal cancer is the second leading cause of cancer–related deaths in the United States. It may affect as many as 1 in 20 persons over their lifetimes. But did you know that an estimated 1 out of every 4 colorectal cancer patients has a significant genetic or inherited component to his cancer? An accurate and complete family history help determine your individual risk factor for colorectal cancer, and will help your physician determine the most appropriate schedule for screening colonoscopy. The presently recommended guidelines state that starting at the age of 50 (45, if African- American), people should undergo routine colonoscopy screening every 10 years. However, this may not be appropriate if there is a significant family history.
There are two forms of inherited colon cancer, which may be acquired even if only one of your parents had it. Familial Polyposis usually manifests itself at an early age, with hundreds of polyps. Ninety percent of those with Familial Polyposis will develop colon cancer by age 50, and oftentimes much younger. Those suspected of having this condition need screening beginning in their teens and yearly thereafter. There is genetic testing that can help determine if this condition is existent in any person. Overall, however, Familial Polyposis represents 1% or less of all colorectal cancers.
Lynch Cancer Family Syndrome
The other strongly inherited form, the Lynch Cancer Family Syndrome (also known as HNPCC, or Hereditary Non-polyposis Colon Cancer Syndrome) is much more difficult to distinguish from sporadic, non-inherited colon cancer, and may represent up to 6% of all cases of colorectal cancer. Family history is the key to suspecting it. It is important to know which family members had colon cancer or polyps, and at what age they developed the cancer or polyps. Additionally, with the Lynch Cancer Family Syndrome, there is a significantly higher incidence of other cancers. It is therefore also important to know if any family members have had cancers that occur in this syndrome. Such cancers include endometrial cancer, bladder and other cancers of the urinary tract, ovaries and stomach. In addition to knowing the history of any cancers or polyps that may have occurred in your first degree relatives (parents, siblings, children), it is also important to know whether any such conditions occurred in your second degree relatives (grandparents, aunts/uncles, cousins, nephews/nieces). The age of onset of these conditions is also important.
The majority of patients who have a strong inherited tendency for colorectal cancer do not have either the Lynch Syndrome or Familial Polyposis. In both of these conditions, you inherit a single defective gene that causes the condition, from one parent or the other. In most families with a strong tendency to colorectal cancer, we believe that you inherit multiple genes, each of which slightly predisposes you to colorectal cancer. As such, there is no blood test that can be checked. For these families, the strategy for preventing colon cancer depends on earlier and more frequent colonoscopy screening. When and how often a colonoscopy is recommended depends on the family history. In general, the more first degree relatives you have with colorectal cancer or polyps, and the younger they were when they developed colorectal cancer or polyps, the stronger the inherited tendency.
So, don’t be embarrassed to talk about health issues at the next family reunion. Reach out to some of your other relatives who may be able to fill you in on family health issues that you may not be aware of. What you find out just may save your life.