Should we test all women for breast cancer-causing mutations?

In this week’s Journal of the American Medical Association, famed geneticist Mary-Claire King argues that all women over age 30 should be tested for cancer-causing mutations in the BRCA1 and BRCA2 genes. King, who made the original discovery of the link between BRCA1 and breast cancer, is one of the world’s leading experts on how mutations in these genes cause cancer.

But her proposed new universal testing policy, which fellow Forbes contributor David Shaywitz calls “audacious,” goes far beyond what other experts recommend. Earlier this year, the highly regarded U.S. Preventative Services Task Force (USPSTF) recommended testing BRCA genes only in women with a family history of breast or ovarian cancer. 

Although there’s no question that King is an expert on BRCA gene testing, I think she’s gone much too far with her latest proposal. She has the science right, but she is far too optimistic about how her recommendation would actually play out. The policy might save some lives, but it would also cause a great deal of pain.

First, it’s worth explaining why King thinks universal BRCA testing is a good idea. In her JAMA article, King and colleagues describe a new study they conducted in Ashkenazy Jews that showed, somewhat surprisingly, that 

“50% of families found to harbor BRCA1 or BRCA2 mutations had no history of breast or ovarian cancer that would have triggered clinical attention." 

In other words, under current policy guidelines, 50% of people who have a damaging mutation in one of these genes will not have their genes tested. Many of them will eventually get breast or ovarian cancer—as King explains, women with harmful BRCA1 mutations have a 60% risk of cancer by age 60, and for BRCA2 the risk is 33% by age 60. That’s a very high risk, though it’s important to keep in mind that many women with these mutations will never get cancer.

With modern DNA sequencing technology, any large-scale genetic BRCA testing program is likely to uncover thousands of mutations that have no harmful effects, and thousands more whose effects are simply unknown. (Aside: each BRCA gene spans about 80-90 thousand nucleotides of DNA, and each of those letters can mutate in 4 ways, changing into one of the other 3 bases or just being deleted. This means there are at least 400,000 mutations possible in each gene, not counting larger deletions. A colleague and I published an article in 2010 describing one such BRCA test.) King is clearly aware that such reporting these mutations to patients would only sow confusion, and she recommends that:

“Testing for BRCA1 and BRCA2 should focus solely on unambiguously loss-of-function mutations with definitive effect on cancer risk…. A VUS [variant of unknown significance] can increase confusion and compromise clinical management; for population-based screening, these variants should not be reported.”

Herein lies one of the biggest problems with King’s idea. We don’t have universal agreement on which mutations have no significance, and even if we did, most physicians are not experts on cancer genetics. In our lawsuit-prone medical culture, there exists an unfortunate tendency to over-treat and over-report everything. 

Thus I fear that if we had wider BRCA testing, clinical labs would report all mutations back to physicians (how could they not?), and physicians in turn would report everything to the patients. The result would be that millions of women would be told "you have a mutation in BRCA1, and we don't know what it means." What's a patient supposed to do with that?

The other problem is that the only treatment to prevent breast and ovarian cancer is surgery to remove a woman’s breasts and ovaries. We don’t have a pill you can take, or lifestyle changes you can adopt, that will dramatically reduce your risk of hereditary cancer. But unlike a cancer diagnosis, the discovery of a BRCA mutation does not mean you have cancer. It simply means you have a risk, possibly a high risk, of getting cancer at a young age. We know from decades of research that people are not very good at evaluating risk. We tend to over-estimate the danger of events that seem very dramatic or visible to us, as cancer is to many people. 

By King’s own estimates, widespread BRCA testing would detect cancer-causing mutations in 250,000 to 415,000 women in the U.S. This estimate assumes the test doesn’t have false positives, which it almost certainly would. All of these women would then be faced with an extremely difficult dilemma: should they have both their breasts removed, or live the rest of their lives in fear of breast cancer? 

This dilemma was famously on display last year, when actress Angelina Jolie revealed in a New York Times article that she’d had a double mastectomy, after discovering that she carried high-risk BRCA mutations. Jolie’s mother died from cancer at the age of 56, and she explained in her article that as a result of the surgery, “ I can tell my children that they don’t need to fear they will lose me to breast cancer.”

King’s proposal is audacious, and it’s well worth debating. But without a better treatment option, telling hundreds of thousands of women that they have a high risk of breast and ovarian cancer carries a potentially enormous cost, both physical and emotional, for these women. Rather than putting huge numbers of women under the surgeon’s knife, we should instead double or triple our investments in research on treatments that may eventually make surgery unnecessary.