please explain BRCA1 and BRCA2

rabbit

I had this test done on Wed, should have the results mid-end of next week. I am so concerned for my sisters if this test comes back postive.

I was told basically that if I am positive for this gene, my chances double at least for it to come back...therefore I should consider a double.

I am doing chemo starting next week, then surgery after chemo.

Can someone please explain the difference between BRCA1 and BRCA2 and why they told me if one of the tests came back negative, they do a 2nd test.... 

otter

rabbit, I'm sorry no one has answered your question yet.  I'll give it a try, although I can't answer some of what you asked.

As for the difference between BRCA1 and BRCA2:  those are the names of two different genes.  Everyone has both of those genes -- the "normal" versions of the BRCA1 and BRCA2 genes are considered "tumor suppressor" genes.  They encode products that are used by a cell to help maintain the integrity of the cell's DNA.  Problems occur when someone has a mutation in either or both of those genes and the normal "tumor suppressor" products cannot be made.

Here is a very good, thorough explanation of BRCA1 and BRCA2 mutations, and how they relate to breast cancer risk:  http://www.cancer.gov/cancertopics/factsheet/Risk/BRCA

This BCO website also has a discussion about BRCA1 and BRCA2, on its "genetics" page:  http://www.breastcancer.org/risk/factors/genetics.jsp

It is true that having a mutation in a BRCA gene is associated with a higher risk of developing breast cancer, and of it recurring if already diagnosed.  BRCA status (being "BRCA positive", i.e., having a mutation in a BRCA gene) is one of the factors used when deciding what preventive measures would be best (bilateral mastectomy, oophorectomy, etc.).

That's about as much as I know about all this.  I can't tell you why there would be a need for a second test.  Perhaps someone else in your family has already been tested, and has a known mutation?  In that case you would be tested for that specific mutation (abnormal gene sequence) first, because that's quick and fairly inexpensive.  If you don't have that precise mutation, they might go back and do a full DNA sequence of your BRCA1 and BRCA2 genes, to see if there is a different mutation. I don't know for sure, though -- I'm just speculating.

I hope you are doing all this through a genetics counselor.  He or she ought to be able to give you good answers to these sorts of questions.

My best to you...  Be sure to stop by in the "Chemotherapy" forum, so you can find others going through chemo at this same time.  It really helps to be able to talk about what you're experiencing.

otter

Mutd

It happens with insurance quite often, that they won't pay for the most sensitive (but also most expensive) test version right away. They would start from covering a less sensitive test (which finds most "problems" but misses some), and move on to more expensive tests only if the first result negative. There are only two BRCA genes, but there are thousands different mutations there, some easier to find than others. So sometimes BRCA testing is done "in stages" too, first looking for the easy answers, then for the harder ones.

In the US, there are three most common scenarios where a BRCA test is followed, if negative, by an additional BRCA test for higher seisnitivity.

1. BRACANALYSIS followed by BART (the first test catches almost all mutations, but a small percentage of more challenging mutations can only be detected by BART ... so if a patient has very strong personal and family history of cancer, but the first test is negative, then it may be up to the 2nd test)

2. Test for 3 "Askenazi Jewish" mutations followed by BRACA... There are very few patients of Jewish origin who have mutations other than the "usual 3 suspects". So a Multisite test for "just 3 mutations" catches almost all of them. But if it is negative, and if the history of cancer is strong, and if the heritage could be mixed, then ... go to step 2

 3. Test for just one family mutation, followed by BRACA. Almost all the time, if there is a mutation in one family member, then all the relatives need to be tested for just this one mutation (too small a chance that there is also a second mutation lurking in the same family). But sometimes the test is negative but the situation is too complicated and it is followed by step 2, a test for all other mutations.

otter

Nice post, Mutd.

rabbit

Thanks all for the info!! I am Jewish and was told my family would be considered "Askenazi Jewish" so that maybe the reason for the 2nd test. I was told the 2nd test costs $700 out of pocket and had to approve that ahead of time, which I did. I start chemo Wed. and at that time, see my onco and he will give me the results of the BRCA tests. I will let you all know.

otter, I am going to check out the chemo forums now

xoxo