How early is an "early onset colon cancer"? How to prevent hereditary colon cancer in current generation of family members? Why history of uterine cancer is important for colon cancer risks? Leading colorectal cancer genetics expert discusses colon cancer. Dr. C. Richard Boland, MD. In familial cases of colorectal cancer the age of cancer onset is earlier than usually. Correct. One of the very interesting aspects of understanding the pathogenesis of colorectal cancer is that sporadic cancers that occur in the general population, without specific germ line mutation, they go through the same general pathways of cancer transformation as the hereditary cancers. Sporadic cancers occur later in life because you have to have acquired mutations in both copies of cancer-causing gene. For example, in most people who have a sporadic adenomatous polyp you get bi-allelic inactivation of the APC gene. Something happens to one allele and then something happens to the other gene allele. It can be mutation, it can be deletion or it can be gene methylation. But if a person has a familial adenomatous polyposis, they are born with germline mutation in one cancer-causing APC gene allele. So every cell in their entire colon is already primed for transformation into cancer, and had a head start down that pathway. Which is why the likelihood of getting a cancer is much higher and the onset of cancer occurs at an earlier age. Dr. C. Richard Boland, MD. Obviously, if somebody knows of the family history of colorectal cancer, especially when colon cancer occurs in the younger family members, they should be vigilant and screen for colon cancer, visit a doctor, and have a preventive program to identify potential precancerous lesions. Correct! If the family history is suggestive of colon cancer, or if there are some biomarkers that we can find - such as microsatellite instability in colon cancer tumor. In these situations germ line genetic testing is appropriate, Because that will tell us whether or not this person has a very high risk of colon cancer. It will also alert us if patient's siblings and children have to be genetically tested. Because when you find one of these germ-line mutations, every first-degree relative has a 50/50 chance of inheriting the same colon cancer-causing gene. and having the same increased risk for colon cancer. And if we find out about this risk before a person ever get sick, then you can completely change the natural history of hereditary colon cancer. It might involve more colonoscopies, it might involve a preventive operation [to remove colon], but it will keep hereditary colon cancer from ever occurring. Dr. Anton Titov, MD.