Wednesday, May 15, 2013

Would you want to know?

You have, no doubt, heard that Angelina Jolie had a prophylactic mastectomy due to the fact that she tested positive for the BRCA 1 gene mutation.  If you didn't hear, then you must be really talented at avoiding all forms of media.  This is a subject that I have opinions about.  I've been working on a couple of posts for awhile, and decided that this was a good time to get them finished.

I can remember in the mid-90s when the media was first talking about "the breast cancer gene."  I was a teenager, but I vaguely remember the conversations that were going on basically asking, "Would you want to know?"  I don't know what the uninformed teenage version of myself thought.

I should say this.  Science is not my strong suit.  I was always a good student, but science was never my favorite.  Once science became more closely tied to math, I enjoyed it a little more.  But words (e.g., English and history) were always my academic strengths.  Followed by math.  Then art and music.  Then science.  And at the very end was P.E.  So if what follows feels a little dumbed down, you know why.  Scientific people will probably cringe at how I've said some of this.

"The breast cancer gene," as it's referred to in popular parlance, is actually a mutation located on one of two specific genes.  Genes are basically little pieces of information that tell the body what kind of proteins to produce.  Some of these genes are tumor suppressors and do damage-control telling cells to stop multiplying into cancerous tumors.  "The breast cancer gene" is actually a mutation on one of two genes, BRCA 1 and BRCA 2, and both are tumor suppressors.  Science has identified the BRCA 1 and BRCA 2 genes and can now test to determine if there are mutations in the gene causing it to not work.  Hundreds of different mutations have been discovered, and some of these are considered to be deleterious (that's bad).  If a deleterious mutation in one of the BRCA genes is detected it basically means that the body will be less able to fight cancer.  A mutated BRCA gene can be inherited from either parent and can be passed on to sons or daughters.  If a parent has a BRCA mutation, then each off-spring has an independent 50/50 chance.  The identified BRCA mutations are fairly uncommon in the general population and are responsible for only 5-10% of breast cancer occurrences.  There are hundreds of known BRCA mutations, and certain deletions have a high occurrence in people who are Ashkenazi Jewish descent or other specific ethnic groups.

The BRCA2 gene is located on the long (q) arm of chromosome 13 at position 12.3.
Here's BRCA 2 on the 13th chromosome.
At some point in the mid-90s, a company patented a methodology for a diagnostic test to identify whether an individual has the BRCA 1 or BRCA 2 mutation.  This company continues to have the exclusive patent for this technology and is, at this point, the sole provider of the test.  I'll perhaps come back to this at some point, because the Supreme Court recently heard the patent case related to this.  Because they are the sole provider of the test, it's basically impossible to get a second opinion.  The testing is done through a saliva sample or a blood draw ordered by a genetics counselor or an oncologist.  Individuals with certain types of cancers, a family history of cancer, or a relative who is positive for the BRCA mutation are likely candidates for testing.

Having a mutation in a BRCA gene does not mean that an individual will get cancer.  There is no crystal ball.  Individuals who test positive for a BRCA mutation have a predisposition for developing cancer in the future, and it significantly increase the likelihood that a woman may develop breast or ovarian cancer during her lifetime.  Unfortunately, BRCA is also often linked to developing these cancers at an earlier age.

In women, BRCA mutations are linked to a higher incidence of breast, ovarian, and fallopian tube cancers.  The increased risks for developing these cancers is significant when compared to the general population:


Average Risk of Breast Cancer by Age 70
Average Risk of Ovarian Cancer by Age 70
General Population
12%
1.5%
BRCA 1
64%
10-60%
BRCA 2
56%
10-60%


Statistics are tricky business though.  Those are averages I found listed in various places, but research has suggested that the risks for breast cancer can be as high as 80% for BRCA carriers.  Other lifestyle and environmental factors also play a role such as hormone exposure, diet and exercise, environmental exposures, and other genetic conditions.   Additionally research has shown that younger women may have higher risks than previous generations because of a number of factors including starting families later, having fewer children, and exposure to chemicals and viruses.

Men are just as likely (50/50) to inherit a BRCA mutation as women.  Men with a BRCA mutation are also significantly more likely to develop breast cancer as compared to the general population.  BRCA mutations are also linked to other types of cancers such as malignant melanoma, pancreatic, colon, and prostate.

Testing positive for a deleterious BRCA mutation does not mean that an individual will develop cancer.  Like I said, science has not yet developed that crystal ball.  There are lifestyle and environmental factors that may alter increase the likelihood that a BRCA carrier will develop cancer.  But upon learning that s/he is BRCA positive, then an individual can take proactive steps:
  • Surveillance (to spot cancers as early as possible)
  • Chemopreventative Drugs
  • Prophylactic Surgery 

With all of this in mind, I ask you: would you want to know?


Come back tomorrow for a continuation...

1 comment(s). Tell me what you think!:

princessquiltandknitalot said...

I have been tested due to family history, I am positive. Knowledge is power.

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