Ten percent of colorectal cancer cases are due to inherited genes. Among these inherited conditions, hereditary nonpolyposis colorectal cancer (HNPCC) is associated with extremely high risk of colorectal cancer. The risk of having colorectal cancer by the age of 70 is 80% for individuals with the HNPCC gene. This is 60 times higher than the risk of colorectal cancer in the general population.
Researchers had identified three genes that are connected to HNPCC: MLH1, MSH2 and MSH6. Under normal conditions, these genes actually help the body to resist cancers. On the other hand, mutations of these genes will make the body more susceptible to cancer, more specifically, colorectal and endometrial cancers.
If you have a first degree relative that has an early onset of colorectal cancer or colorectal cancer classified as HNPCC, the chance is that you might have the mutations as well. First degree relatives include your mother, father, sister, brother, son or daughter. It is therefore important to test whether you have mutations in MLH1, MSH2, and MSH6
Recently, Myriad Genetics, a company specializing in molecular diagnostics, has developed COLARIS to test for mutations in MLH1, MSH2, and MSH6.
It is estimated that only 1% of the people that might have HNPCC undergo genetic testing. COLARIS is a simple genetic test that will help health care providers to manage HNPCC.If the patient has the HNPCC gene, it is recommended that patients with HPNCC to undergo colonoscopy frequently every 1-3 years. Screening should start at the age of 20 or at 10 years from earliest diagnose of CRC in family. Chemoprevention is another option being investigated in reducing risk of HPCC.
Myriads also have several other products along this line: COLARIS AP is a test for hereditary polyps, BRCA1 and BRCA2 for breast cancer.
Aarnio M et al. Cancer risk in mutation carriers of DNA-mismatch-repair genes. Int J Cancer. 1999;81:214-218.
Vasen HFA et al. Cancer risk in families with hereditary nonpolyposis colorectal cancer diagnosed by mutation analysis. Gastroenterology 1996;110:1020-1027. 4.
Burke W et al. Recommendations for follow-up care of individuals with an inherited predisposition to cancer. I. Hereditary nonpolyposis colon cancer. Cancer Genetics Studies Consortium. JAMA. 1997;277:915-9.