Memorial Sloan-Kettering has established a registry for families who are affected with various forms of hereditary colorectal cancer.
This registry will help researchers learn more about the genetic causes of colorectal cancer and aid in the development of new ways to prevent, diagnose, and treat cancers of the colon and rectum. Participation can be educational for families by helping them learn more about their colorectal cancer risk. For patients already diagnosed with a hereditary colorectal cancer, the registry will help to keep them abreast of new research that may affect their medical care. For eligibility and contact information, please visit our clinical trial database.
About Genetics & Colorectal Cancer
About 5-10 percent of all cases of colon cancer are thought to berelated to heredity. Physicians today recognize two diseases that account for some, but not all, of those cases: familial adenomatous polyposis (FAP) and hereditary non-polyposis colorectal cancer (HNPCC), which is also known as Lynch syndrome.
Familial Adenomatous Polyposis
People who have inherited the FAP syndrome -- accounting for less than 1 percent of all colorectal cancers -- usually develop hundreds or thousands of colon polyps at a young age. The polyps are benign, but some become cancerous over time. For that reason, annual colon examinations are recommended as early as elementary school, and a preventive, or risk-reducing, colectomy -- surgical removal of the colon -- is also recommended by their late teens. Without a colectomy, the risk of developing colorectal cancer approaches 100 percent.
Hereditary Non-Polyposis Colorectal Cancer
Hereditary non-polyposis colorectal cancer (HNPCC) is a more common form of inherited colorectal cancer, accounting for about 3-5 percent of all colorectal cancers. HNPCC also develops at a younger age than non-inherited colorectal cancer, although not as young as in patients with FAP. People with HNPCC typically develop cancer while in their 40s. It is also known to be a fast-growing form of cancer. About 70 percent of people who carry this genetic mutation will develop colon cancer by the age of 80. They are also at much higher risk for uterine, ovarian, stomach, kidney, and other cancers. A study by Memorial Sloan-Kettering researchers found that people who develop colorectal cancer before age 40 are more likely than older patients to have HNPCC. People with HNPCC are advised to have annual colonoscopies because approximately 70 percent of people who carry this genetic mutation will develop colon cancer by the age of 80.
Other Hereditary Colorectal Cancers
A third form of inherited colon cancer -- one that affects only people of Ashkenazi Jewish descent -- was recently discovered. This syndrome does not cause hundreds of polyps like FAP or a very high risk of cancer like HNPCC. Further studies to clarify this form of inherited cancer are in progress.
Microsatellite Instability
When mutations occur in genes that help to repair genetic errors, these genetic errors multiply in the cells. This is known as microsatellite instability (MSI) is present in many early age-of-onset colon and rectal cancer. Also, young patients with MSI-positive tumors have an increased risk for HNPCC.
Previous retrospective studies have suggested that patients with MSI-positive tumors tend to have better overall survival compared to patients with MSI-negative tumors. Our investigators have now started a clinical trial to determine if having an MSI-positive tumor influences survival in people who develop colon or rectal cancer before age 50, and to learn if having an MSI-positive tumor increases the risk of developing colon polyps and/or additional colon or rectal cancers in the future. By learning more about the risk associated with this particular type of colorectal tumor, physicians will be able to develop guidelines to follow and treat individuals at increased risk. For more information, please visit our clinical trial database.
Our Clinical Genetics Service
People who have a strong family history of colorectal cancer, or who suspect their families might carry one of the genetic mutations for colorectal cancer, should discuss the possibility of genetic testing with their doctors. Because a large number of colon cancers are believed to be related to family hereditary patterns, we look at the patient not just as an individual but as a representative of a family, and strive to get all family members involved in cancer prevention and screening. Memorial Sloan-Kettering's Clinical Genetics Service offers counseling and education on colorectal cancer risk, as well as regular screening examinations, to individuals and their families who might be affected by these inherited syndromes.
