Just one per cent of patients who contract the illness have hereditary nonpolyposis colorectal cancer hereditary nonpolyposis colorectal cancer (HNPCC), according to the study of 1-100 patients reported in the Journal of the National Cancer Institute.
Previous studies have reported rates of 5-13%.
227 of the patients had a family history of the disease and 16 had HNPCC. All the HNPCC patients in the study were under the age of 65.
As well as being the commonest of the genetic forms of the disease that are known about, HNPCC is a fast developing form of the disease and usually strikes patients at a relatively young age. It is characterized by sudden growth of tumors and an absence of pre-cancerous polyps, according to the research team from the University of California, Irvine, USA.
Researcher Hoda Anton-Cutler said: "Studies have shown that family history is a strong factor in determining the risk of getting colorectal cancer, so it is very important to determine the exact rates of its inherited forms.
"This study helps us pin down the risks of inheriting the disease and indicates that researchers still need to look for other genetic interactions that may lead to colorectal cancer. While we've shown that HNPCC is not as common as we thought, other unknown genes could be contributing to the risk of getting colorectal cancer."
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