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Testing for Hereditary Colorectal Cancer

New guidelines aim to help doctors determine whether others face risks

WEDNESDAY, Feb. 18, 2004 (HealthDayNews) -- Revised criteria for testing for a hereditary type of colorectal cancer have been issued by a group of international experts.

The revised Bethesda Guidelines, which appear in the Feb. 18 issue of the Journal of the National Cancer Institute, should help doctors determine if a patient's colorectal cancer is a specific form that is inherited, which may mean the person's family members have an increased risk of the disease.

Hereditary nonpolyposis colorectal cancer (HNPCC) usually occurs in people younger than age 45. It can lead to development of cancers in a variety of tissues, including the colon, rectum, endometrium, stomach, ovaries, brain and skin.

HNPCC results from inherited genetic mutations. That means that family members of people with HNPCC also may have the genetic characteristics that put them at increased risk for cancers.

A major genetic characteristic of HNPCC tumors is the instability of short repeated sequences of DNA known as microsatellites. This instability occurs when mutations in genes responsible for repairing damaged DNA cause microsatellites to become longer or shorter.

The revised criteria suggest that tumors from colorectal cancer patients should be tested for this instability. Subsequent genetic testing, to confirm a mutation in one of the genes responsible for colorectal cancer, is recommended if:

  • The patient is younger than age 50;
  • The patient has multiple tumors in the colon or in other areas known to be caused by the same mutations, either at the same time or occurring over a period of time;
  • A patient younger than age 60 has colorectal cancer that has microscopic characteristics indicative of the DNA instability;
  • The patient has at least one first-degree relative who had colorectal cancer at age 50 or younger;
  • The patient has at least two first- or second-degree relatives who had HNPCC-related tumors at any age.

More information

To learn more about colorectal cancer, visit the National Cancer Institute online.

SOURCE: Journal of the National Cancer Institute, news release, Feb. 17, 2004
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