Alas, this study is being over-hyped.
You can read it here yourself:
Now, I’m not an oncologist (psychiatry is my field), but I do know a bit about statistics*, so let’s wade into this:
The study looked at 5,783 women who carried the genes in question, and who were followed up for over 5 years.
2,270 of these chose not to undergo the oophorectomy.
2,123 did so at baseline.
1,390 did so at some point during the follow-up.
46% of these women already had breast cancer at baseline, so we’re already talking about a high-risk population.
36.6% of them used oral contraceptives, which can bollix up your results (it’s a “confounding factor” to use the jargon.)
Now let’s look at results:
Of the 2,270 who didn’t undergo surgery, 4.8% (108) developed cancer. (Let’s call them Group A.)
Of the 2,123 who did at baseline, 1.1% (23) developed cancer. (Let’s call them Group B.)
Of the 1,390 who did so later, 4% (55) developed cancer. (Let’s call them Group C.)
In other words, the 5-year risk of cancer is only 4.8% even if you don’t undergo the surgery.
Of course, when you compare Group A and Group B and do some high-powered statistics, you will find that the surgery has reduced the risk of cancer by around 80% (you can work this out roughly just by looking at the percentages.) This difference is large enough that it isn’t due to chance alone - i.e., it is “statistically significant”. By way of comparison, though Group C seemed to do better than Group A, the difference (4 vs 4.8%) could just be a chance variation; it is not “statistically significant”.
The authors have used a standard trick - presenting relative risks - to make the surgery look better than it does. 80% sounds impressive. In reality, we’re talking of a drop in odds from 4.8% to 1.1% over 5 years, nothing more, nothing less. The majority of women who didn’t undergo the surgery - 2162 of the 2270 women - did not develop cancer.
Bottom line: 80% reduction from 4.8% isn’t really that big a deal.
Based on this study, I wouldn’t recommend the procedure to anyone (regular monitoring and checking for signs of early cancer would do as well, but I’m not an oncologist, so I’ll stop there.) This is what happens when the media reports results that are disingenuously presented by a research group seeking attention.
(And yes, I do this for a living.)