Monday, August 9, 2010

DNA Sequencing: Useless?

Adam Keiper, editor of the excellent journal of science and society The New Atlantis, posts to the Corner about an interview by Craig Venter in which he states that the Human Genome Project has yielded "zero" fruit.

Specific DNA sequencing efforts certainly have yielded fruit. Venter points out that finding a gene that adds only 1-3% to the likelihood of getting some disease is of no clinical value: also true. Keiper takes this further:

For better or for worse, our limited genomic knowledge is already influencing people's decisions about important matters. Some women who learn from DNA tests that they have a genetic susceptibility to breast cancer are electing to undergo mastectomies even though they don’t yet have, and might never develop, the disease.

It's not clear Keiper is applying Venter's numbers to his own conclusions, but if so he's trying to take his argument a bridge too far. The BRCA mutations that have been shown to correlate highly with breast cancer change a woman's likelihood from a baseline of about 6-8% by age 70, to a hefty 85%. That is, if you have the BRCA mutation, you have an 85% chance (better than 5 in 6) of getting breast cancer by age 70. That's a huge result, and it's not surprising that some women found to have the mutation would choose to circumvent the disease by having double mastectomies.

Before women reading this rush off to get genetic testing, I should point out that the BRCA mutation is quite rare - well under 1% of the population - and only a small percentage of breast cancer cases involve it. So in that sense, its clinical value may be small since the test is relatively expensive. But wouldn't a cheap BRCA test be of enormous value to, say, a woman of 30 who was considering starting a family?

The larger point Venter and Keiper make is quite right: the HGP was overhyped. But they go a bit too far to deflate the hype. It did have some value.

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