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Genetic Testing For Breast and Ovarian Cancers not Sufficient Enough for Recommendations of Invasive Prophylactic Surgeries - Study Shows

March 21st 2006

Genetic Testing For Breast and Ovarian Cancers not Sufficient Enough for Recommendations of Invasive Prophylactic Surgeries - Study Shows

Genetic Cancer Risks

There are some genetic tests that can be performed to determine the risk of breast and ovarian cancer, but not all cancers are associated with identified gene mutations. According to research by Mary-Claire King, Ph.D., of the University of Washington, Seattle, lifetime risks of breast cancer are as high as 80 percent among U.S. women with mutations in BRCA1 and BRCA2 genes.

Among white women in the US, mutations in the BRCA1 and BRCA2 genes account of 5 percent to 10 percent of the breast cancer cases.  The risk for young women with these particular inherited gene mutations is increasing.   

There are other gene mutations to look out for.  Inherited mutations in other genes, including CHEK2, TP53 and PTEN, can also influence risk of cancer.  There are some advantages for getting tested early for these and other gene mutations.

 

There are clinical options available for women at high genetic risk of breast cancer including screening starting at a younger age, the use of highly sensitive detection methods, and prophylactic surgeries of the ovaries or breast.  The prophylactic surgeries are highly invasive, so it should be particularly important to distinguish mutation carriers from non-carriers with similarly severe family histories.

The genetic testing in as-yet-unaffected women with severe family histories of breast or ovarian cancer has become an integral part of some clinical practices. 

Between 2002 and 2005 the researchers evaluated DNA and RNA samples from 300 breast cancer probands. A proband is an initial member of a family to come under study.  They used multiple different screening approaches to identify mutations of all genomic classes in BRCA1, BRCA2, CHEK2, TP53, and PTEN.

 

The study was conducted to determine the frequency and types of undetected cancer-predisposing mutations in BRCA1, BRCA2, CHEK2, TP53, and PTEN among patients with breast cancer from high-risk families.  These families included 4 or more cases of breast or ovarian cancer. 

The researchers found “that of the 300 probands, 52 (17 percent) carried previously undetected mutations, including 35 (12 percent) with genomic rearrangements of BRCA1 or BRCA2, 14 (5 percent) with CHEK2 mutations, and 3 (1 percent) with TP53 mutations. No inherited mutations were detected in PTEN. At BRCA1 and BRCA2, 22 different genomic rearrangements were found. Of these, 14 were not previously described and all were individually rare. Inherited rearrangements of BRCA1 were more frequent among probands diagnosed when younger than 40 years (16 percent) than among probands diagnosed when 40 years or older (6.5 percent).”

 

The point to the study was to determine if genetic testing was sufficient enough to determine if a woman should undergo invasive and expensive risk management options.  The authors wrote, “Our results suggest that genetic testing, as currently carried out in the United States, does not provide all available information to women at risk. Our data indicate that 12 percent of those from high-risk families with breast cancer and with negative (wild-type) commercial genetic test results for BRCA1 and BRCA2 nonetheless carry cancer-predisposing genomic deletions or duplications in one of these genes."

"The clinical dilemma is what to offer to women with a high probability of carrying a mutation in BRCA1 or BRCA2 but with negative commercial test results. Technically, the answer is at hand. The mutations identified in our study that were missed by commercial testing are detectable using other approaches that are currently available," the researchers write. They add that for families testing negative (wild type) for BRCA1 and BRCA2 by conventional sequencing, multiplex ligation-dependent probe amplification (MLPA - a molecular method to detect genetic variation) followed by sequence confirmation of breakpoints in patients' genomic DNA is the current best choice for evaluating the wide range of genomic rearrangements in BRCA1 and BRCA2. Clinical testing using MLPA is currently not available in the U.S.

"As more breast cancer susceptibility genes of different penetrances are identified, clinicians will be increasingly challenged to offer the most appropriate genetic tests, to assist patients in interpreting the results, and to optimize risk reduction strategies," the authors conclude. "Effective methods for identifying these mutations should be made available to women at high risk."

  
 
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By Dan Wilson
Best Syndication

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Copyright 2005 Best Syndication                                            Last Updated Saturday, July 10, 2010 09:50 PM