Importance of Family History and the Risk of Colon Cancer
3/23/2010 - Chances are you know someone, possibly a family member, who has been diagnosed with colorectal cancer. Approximately 150,000 individuals in the U.S. were diagnosed with colorectal cancer in 2009 making it the third most common cancer. While we do not always know the specific cause of colon cancer, we do know that certain risk factors influence the likelihood of developing colon cancer. These include age, history of colon polyps, dietary factors, smoking, and family history.
One quarter of patients diagnosed with colon cancer will have a relative with colon cancer which suggests a potential for an inherited, familial risk. Yet, too often family history is not examined thoroughly enough during a medical check-up even though it can dramatically influence when and how frequently a patient should be screened for colon cancer. Having just one close relative (brother, sister, or parent) with colon cancer, or even a precancerous polyp, doubles your risk for developing colon cancer in your lifetime. The age of the relative at the time of diagnosis is important as well and can affect screening recommendations. If your close relative was diagnosed with colon cancer in their 50’s, then colon cancer screening should begin at age 40 rather than at age 50 which is the recommendation for the general population.
When more than one individual has had colon or another cancer in the family, an inherited colon cancer syndrome may be present. A cancer syndrome describes a specific pattern of cancer within a family which appears to have a hereditary or genetic connection because it has been observed in multiple, unrelated families. Generally the cancers occur more frequently and at an earlier age when compared to “sporadic” cancers. Sometimes a specific genetic test is available for a cancer syndrome which can aid in determining who “inherited the risk” and therefore requires additional cancer screening.
How do I know if there is a colon cancer syndrome in my family? The answer requires investigating the family medical history and searching for potential clues. This detective work can be initiated in the privacy of your home using confidential, online family history tools such as MyGenerations. Such tools help look at the “pattern of clues” in the family to better personalize the cancer risk you face. It can then be shared with your physician to help guide appropriate cancer screening and possibly genetic testing.
Some clues are more obvious than others. Colon cancer often starts as a polyp which grows out from the colon wall. Usually these are benign growths which do not evolve into a cancer, but some polyps, termed adenomas, have the potential to become a cancer if not removed during colonoscopy. In some families, members produce hundreds if not thousands of these pre-cancerous polyps which dramatically increases the risk for developing colon cancer and can alert physicians that a specific gene (APC) may not be functioning correctly because it is altered, that is, has a mutation. Most clues are more subtle, requiring a closer look at cancers within a family.
The cancer patterns are not always intuitive, and it is important to discuss your family cancer history with a medical professional experienced in recognizing such patterns. For example, colon cancer seen with uterine cancer in the family is suggestive of Lynch syndrome, also known as Hereditary Non-Polyposis Colorectal Cancer (HNPCC) syndrome, which accounts for approximately 2% of the colon cancers diagnosed each year.
Even with advances in genetics, family history remains the cornerstone of cancer risk assessment and personalization of care. Using family history tools and discussing results with your physician can help you understand your risk and establish a tailored cancer screening plan.