Is Colon Cancer Hereditary?

Dr. Timothy Hoops
Last Modified: November 1, 2001

Dear OncoLink "Ask the Experts,"
I have just been diagnosed with a Dukes B adenocarcinoma of the colon, which has now been removed, and I am about to start a course of chemotherapy (5-FU). I am only 26 years old and have been told it is very unusual for someone of my age to get bowel cancer. Doctors are saying that it is most likely a genetic cause. Can you explain how this happens?  
Thank you

Dr. Timothy Hoops, Clinical Assistant Professor of Medicine in the Gastroenterology Division at the University of Pennsylvania and Director of Gastroenterology at Penn Medicine at Radnor, responds:

Colon cancer is very unusual in people younger than 50 years old, but as you and several others in the news can testify, it can and does occur. In many situations, this is related to the inheritance of one of several genes that predispose that person to colon cancer. Since it is related to these genes, one usually sees other members of the family affected with colon cancer or other related cancers.

No mention is made of any family history in this case. If there is a family history, it may be worthwhile to explore that possibility. If there is no family history of cancer, it is still possible that this could be related to a gene defect. Presumably, this would be due to a new mutation. Some have suggested that anyone with an early-onset colon cancer should be tested for genetic mutations regardless of family history. The advantages of doing this would be to get a better understanding of what lead to the disease, to increase awareness of other possible associated tumors and to know what the risks are for transmission of the cancer susceptibility to children (if a mutation were found, they could also be tested as they grew older).

It is important to understand, however, that the chance of finding a genetic mutation is still relatively small. The important thing for anyone with colon cancer is that after the treatment phase, an active surveillance program is necessary given the risk for the development of new cancers. Additionally, any first-degree relatives should also undergo colonoscopies as they are also at a significantly increased risk for colon cancer.