These Genes Don’t Fit

A section of DNA; the sequence of the plate-li...

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Last month, I decided to take the plunge and drive north to Seattle to speak with a genetic counselor to determine whether there’s any likelihood that I developed breast cancer as a result of a malfunction of my genes.

The current numbers from the experts say that only 5% to 10% of women who develop breast cancer have a family history that can be attributed to a genetic defect passed down through relatives (either male or female). So, despite what the various media might lead you to think, most women who develop breast cancer do not have a genetic defect, at least not one that we can yet identify.

Still, some of the recent research about triple-negative cancer raises the question of a greater likelihood of a genetic defect (most commonly a mutation of BRCA1), and so I again had to consider whether to sign up for genetic testing.  Both my oncologist and the naturopath said it was unlikely and they didn’t see the need to progress to testing, but then came a report from the New England Journal of Medicine, which charted a higher rate of genetic defects among those of us with triple-negative or basal types of breast cancer. Since I do have a son and a daughter, each of whom might be affected if I have such a mutation, I had to lay the issue to rest in my own mind.  (And as a couple of people put it to me, “The mutation has to start somewhere!”)

So I asked the oncologist to refer me to the counselor at the University of Washington, home of the highly regarded Fred Hutchinson Cancer Center, one of the foremost cancer research centers in the country.

And what I learned, once again, is that life is rarely a matter of a simple yes or no. Yes, genetic defects can play a role, but that role is much more complex that simply saying a defect exists or doesn’t.  Science is amazing in what it has uncovered about human life, but when it comes to issues like genetics, there are more unknowns than facts. Even my astute daughter figured out that, should I have a genetic mutation, her chance of developing breast cancer is only 50-50.  (And who says they don’t teach substance in schools these days?  She studied the basics of Mendelian genetics and chemotherapy in science last year.)

As I mentioned in earlier posts, I have the great benefit of coming from a large family – 8 aunts and uncles, 35 first cousins – and I know much of the history of the illnesses passed down among these relatives. With the exception of my maternal grandmother, there are absolutely no other cases of breast cancer in that extended family.  But that fact is not enough on its own to rule out a hereditary cause because some syndromes leading to breast cancer are associated, for example, with sarcomas and leukemia, or digestive and thyroid tumors. As this information from the American Cancer Society shows, the various risk factors and genetic influences — BRCA 1 and 2, ATM, p53, CHEK2, PTEN — are much too complex to pin down in any single case.

After carefully recording the details of medical problems in my extended family, the genetic counselor I spoke with determined that the chance of my having a genetic defect is only about 5%. That number doesn’t explain why I got the disease, but it goes a long way toward making me feel more optimistic for my children’s futures.

This is a set of genes I’m quite happy don’t fit.


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