If you were offered a crystal ball which could predict whether you will eventually develop cancer, would you accept?
Approximately 10% of breast and ovarian cancers can be linked to some hereditary predisposition. Some of the signs that a person might be at this type of risk include personal or family history of:
1) Breast cancer under age 50
2) Ovarian cancer
3) Multiple breast cancer patients in a family
4) Breast cancer along with Central or Eastern European Jewish ancestry
5) Male breast cancer.
Today I went to have a small vial of blood drawn so that I could submit a genetic sample to Myriad Genetic Laboratories in Salt Lake City. Over the next few weeks, scientists at the lab will be closely scrutinizing my DNA to help determine whether a mutation or mutations in my genetic makeup might have been at least partially responsible for my breast cancer. In particular, they will be looking at two tumor suppressor genes called BRCA1 and BRCA2 for any deletions or alterations. Mutations in these two genes are responsible for the majority of hereditary breast and ovarian cancers.
A mutation does not mean that the carrier will develop cancer; it merely implies an increased risk. For example, the probability that a woman without a mutation in BRCA1 or BRCA2 will develop breast cancer before age 50 is roughly 2%. A change in the genetic code, however, raises that <age 50 probability to the neighborhood of 33-50%. The risk for breast cancer up to age 70 is even more significant: without a BRCA change, it is 7%, but with an alteration in BRCA 1 or 2, it jumps to 87%. This would be a 13% chance that an affected woman would not develop breast cancer by the age of 70! Mutations in BRCA1 and BRCA2 also pose additional risk for ovarian cancer (2% for mutation-negative and up to 44% for mutation-positive patients), and to a lesser extent, for colon, earlier-onset prostate, pancreatic, and other cancers.
The gene mutation is handed down with 50% probability from either mother or father to child. My family history exhibits at least a couple of the risk signs listed above; Earl’s family shows even more. Both I, and Earl in the near future, are being tested not only for our personal health concerns, but even more for the welfare of our children and their children.
A few important caveats must be allowed. Test results range from negative to uncertain to positive. The uncertain category means that some alterations to the genetic code were detected, but the implication of those is unknown (i.e., no yet known effect on cancer risk). Even if the test result is negative, there might be a mutation in a completely different gene causing hereditary breast or ovarian cancer. And, again, testing positive does not indicate certainty of an eventual cancer, merely an elevated risk. Even if someone doesn’t end up developing cancer in his/her lifetime, that person’s mutation can still be passed on to children, thus “skipping” a generation.
So perhaps the prognostication is closer to a Magic Eight Ball than a crystal ball. Just as likely as “Without a Doubt” is “Reply Hazy – Try Again.” Personally, I’m hoping for “Outlook Good.”
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