New method identifies important mutations behind hereditary non-polyposis colorectal cancer Colorectal cancer is the third most common form of cancer. While 90% of cases are in people older than 50, there is an as-yet unexplained rising incidence in younger people. Family history ranks high among risk factors for developing colorectal cancer, and people with such a history are often advised to get more frequent screening tests or start screening sooner than the recommended age of 45 years old. Those with a family history of cancer often seek out genetic tests to look for mutations linked to cancer risk. However, those tests don't always provide helpful information.