An international group of experts has updated a set of criteria for testing patients with colorectal cancer to determine whether the cancer is a specific type that is inherited and therefore may mean that a patient's family members are at an increased risk of the disease. The revised Bethesda Guidelines are published in the February 18 issue of the Journal of the National Cancer Institute.
Hereditary nonpolyposis colorectal cancer (HNPCC) usually occurs in patients younger than age 45 and can result in the development of cancers in a variety of tissues, such as the colon, rectum, endometrium, stomach, ovaries, brain, and skin. A major genetic characteristic of HNPCC tumors is microsatellite instability (MSI). Microsatellites are short repeated sequences of DNA, and MSI results when mutations in genes that are responsible for repairing damaged DNA cause microsatellites to become longer or shorter. Cancers that exhibit MSI account for about 15% of all colorectal cancers.
Because HNPCC results from inherited mutations, it is possible that family members of patients with HNPCC also have the genetic characteristics that put them at an increased risk for cancers associated with a particular mutation. In 1997, a panel of experts created the Bethesda Guidelines, which outlined criteria for testing tumors from patients with colorectal cancer for MSI so scientists can better understand the development process of HNPCC and identify patients with the syndrome. Such testing would also allow affected family members to take measures to reduce their risk of developing HNPCC-associated cancers.
In a commentary, Asad Umar, D.V.M., Ph.D., of the National Cancer Institute, and colleagues summarize a meeting in 2002 at which experts looked at the most recent evidence about HNPCC gene mutations and revised the Bethesda Guidelines for testing colorectal tumors for MSI. The revised criteria suggest that tumors from patients with colorectal cancer should be tested for MSI and subsequent genetic testing to confirm a mutation in one of the genes responsible for HNPCC in the following situations:
1. The patient is younger than age 50.
2. The patient has multiple HNPCC-associated 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.
3. A patient younger than age 60 has colorectal cancer that has microscopic characteristics that are often indicative of MSI.
4. A patient has one or more first-degree relatives who had an HNPCC-related tumor at age 50 or younger.
5. A patient has two or more first- or second-degree relatives who had HNPCC-related tumors at any age.
The authors of the commentary also make recommendations about specific MSI tests that should be used for these patients, and they make suggestions for future research directions to better understand the development of HNPCC and HNPCC-associated diseases.
Source: Eurekalert & othersLast reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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