October 11, 2008 - Genetic Testing for BRCA Gene

Yesterday I had an appointment with a genetic counselor to learn about genetic testing and what a positive result (for the BRCA-1 and BRCA-2 gene) would mean for me and my blood relatives.

Here was what the genetic counselor explained to me. At least, this is what I remember that she said to me. Caveat: Please do not assume this information is accurate. Genetic counselors went to college for this and they get paid to explain this to you, so I would use one if you need an accurate description!

Here goes:

Ninety percent of cancers are sporadic, meaning they were most likely not created due to a hereditary nature. Five to ten percent of cancers are hereditary. Five to ten percent are familia, but I will not go into that at all here (since I know nothing about it).

Thinking about a single cell in a person's body....
Everyone has two copies of every gene in every cell. Let's think about one cell and one set of genes. And let's say sunlight (for example) damages one gene, then you're left with only one of the two genes. No problem. Let's say the next summer that remaining gene gets destroyed by sunlight. Now the cell that is missing both of those genes (if it needs to grow) starts growing and doesn't know when to stop. It can cause cancer. That's how the sporadic cancers begin.

For the hereditary cancers....
Still thinking about a single cell and each cell having two copies of every gene in every cell....
From mom or dad, there might already be one missing gene in every cell of a person's body. Now if that remaining gene get's destroyed by something (e.g., sunlight), it can cause cancer.

So you can see that HEREDITARY cancers happen because they NEED only ONE chance to destroy a gene and have cells grow out of control. Whereas SPORADIC cancers NEED to have BOTH genes get destroyed before the cells have a chance to grow out of control.

I had a blood test yesterday to test for the BRCA gene. It's called BRACA testing, and it tests specifically for the BRCA genes, which are the genes known to be associated with breast cancer. I'll get the results in a few weeks. Of course, I won't share the results on my blog. The results, if shared, can have an impact on future employment, medical insurance, etc.

I expect the result to be negative. What does a positive result mean? A positive result means that I have a 40 to 50% chance of getting ovarian cancer. Yuk. I don't remember my chances of a recurrence of breast cancer. I'll have to email my counselor to find out. A positive result would also mean that my sister and my son have a 50% chance of also testing positive. Since my son is only 11, we wouldn't even discuss testing until he is an adult, and it would be his decision to get tested. If he chose to test and he tested positive, then he would have a 6% chance of getting male breast cancer and a 20% chance of getting prostate cancer. If there's a positive result, my sis might want to get tested to see if she also carries the gene. If it's negative, we can conclude that she is also negative. If she was to test positive, then she would have an 85% chance of getting breast cancer over her lifetime.

I hope that wasn't too boring, and I hope it was semi-accurate!!!

Monday is my final radiation treatment. Woo hoo!