Ultimately I've come to a few conclusions:
* 23andMe doesn't screen for my family's mutation or the vast majority of BRCA mutations.
* The incredible diversity of mutations that can occur in the BRCA genes makes it difficult to study specific types of mutations.
* Traditional genetic testing is much more reliable than 23andMe, BUT geneticists still struggle to fully understand the impact of most BRCA mutations on breast cancer risk.
And Here's why:
“may confer as much as an 84% risk of breast cancer and a 27% risk of ovarian cancer by age 70.”
Finally, I learned that there is an entirely separate nomenclature for BRCA mutations. Complicating matters more, this nomenclature has been changed multiple times so the same exact mutation can be titled two separate ways (Ex. “c3303G>T” or “c3075G>T”). Data sources like 23andMe and NCBI record the position of a mutation or the unique SNP designation as a point relative to the entire genome, whereas BRCA mutations are named as points relative to the gene alone. I needed to translate between these scientific languages to locate the position of our family's mutation in 23andMe data.
- BIC documents 1776 unique BRCA1 mutations and 1998 unique BRCA2 mutations.
- 45% of identified BRCA1 and BRCA2 mutations have been found to increase a person’s risk for breast cancer --BUT we really have no idea how risk varies by specific mutation type.
- 2.9% of the mutations observed in BRCA1 and BRCA2 have been found to be completely and utterly meaningless— Great! If you have one of those mutations, you’ve got nothing to worry about.
- (BEWARE, DEPRESSING PART à) A whopping 51.5% (“MOST!”) of documented mutations are of unknown clinical importance – AKA we have no idea how dangerous they are, if at all.
1) Even professional genetic testing is still very limited. Unfortunately, we can’t definitively say whether or not more than half of BRCA gene mutations increase a person’s risk for developing breast cancer.
2) 23andMe screens for 3/3664 possible mutations in the BRCA1 and BRCA2 genes that could be associated with higher risk for breast cancer. That’s only 0.08 of one percent of the ways the genes could mutate to increase risk!
3) I suspect a lot of people may mistakenly interpret a test result like Heather’s as reassurance that they’re not at high risk for breast cancer… and that’s dangerous.