Thursday, May 24, 2007
With all apologies to my good friend Rick Vidal at My Biotech Life I am here to report a tremendous disservice done to all of us western hemispherians(is that even a word?) by the Portuguese.
On the 20th of May in the Journal of Clinical Oncology an article was presented examining the BRCA2 rearrangements in 210 high risk cancer families. The rearrangement they described, occurs in 1/3 of all male breast cancers that they identified.
Why the big deal? Well, only 7 rearrangements to date have been described in the BRCA2 gene. In addition these rearrangements are not picked up in point mutation sequencing. Which brings me to a very important point regarding genetic testing. No Test Gives a Yes or No Answer. These tests require skilled interpretation as well as counseling to evaluate for further need of testing. This is the case with BRCA rearrangement analysis. This topic was covered by here. According to a study in JAMA back in 2006, several families testing NEGATIVE for BRCAs actually had rearrangements in these genes, leading to faulty function and cancers.
So here's where I say Blame Portugal. This founder mutation they identify is the most reported rearrangement for BRCA2. This is screwing up physicians who are only testing for BRCA point mutations. Such misleading results can give families a false sense of safety that they are not BRCA carriers.
"Portuguese people have been intensely migrating throughout the world since the XVth century first as trading sailors, and later as emigrant families, but most of the time crossing their genetic background with other people's. For this reason the researchers suggest that screening of this BRCA2 mutation "should be extended to all high-risk breast cancer families with Portuguese ancestry", in order to identify grater numbers of healthy women with a higher-than-average breast cancer risk, and offer them adequate preventive measures. "
The Gene Sherpa Says: I agree. Cancer in your family plus Portuguese ancestry equals BRCA rearrangement testing as well as indicated genetic screening. This is why it is so important to know your family history and ethnicity.