Up to a third of colon cancer cases exhibit a moderate form of inheritance. There are certain families in which colorectal cancer occurs much more frequently than would be expected by pure chance. It appears that these patients have been born with one of the abnormal (“mutated”) genes already present in each of their cells. This makes the likelihood of collecting the additional random mutations that can lead to cancer much less of a rarity. Members of such a family carry a higher risk of developing colon cancer, often at an early age.
It has been shown that having a first-degree relative (parent, brother, sister or child) with colorectal cancer doubles the risk of developing cancer. For this reason, a detailed family history will be obtained during the visit. Patients will be asked to provide information regarding any cancers and the age of diagnosis for all family members. There should be concern if a family has more than one relative with colorectal cancer or if the relative developed that cancer before the age of 50. In some cases, genetic testing for polyposis colon cancer syndromes or non-polyposis colon cancer syndromes may be warranted.