Monday, August 06, 2012
Just in case you still give to Susan G. Komen . . .
. . . one more reason to send your money elsewhere. This is from Steven Woloshin and Lisa Schwartz at Dartmouth, who review Komen's advertising urging women to get screening mammograms. "Komen's public advertising gives women no sense that screening is a close call. Instead, it simply tells women to be screened, overstates the benefits of mammography, and ignores harms altogether."
They specifically critique an ad that claims that "early detection saves lives. The 5-year survival rate for breast cancer when caught early is 98%. When it's not? 23%."
I know my readers are smart enough to see right away what is wrong with this assertion. It's called lead time bias. Suppose you could has a time machine, and you first identified a group of 100 women who died of breast cancer at age 70. Then you went back in time and gave half of them a mammogram at age 65. The other half would have been diagnosed later, when their tumor became palpable. The ones who got screened would have five year survival of 100%; the ones who did not, would have five year survival of 0%. That's a big difference, but it's completely meaningless, except that the screened women had three or four years more to be sick and undergoing surgery and chemotherapy.
The best available estimate we have now is that mammographic screening reduces the chance that a women in her 50s will die of breast cancer within 10 years from .53% to .46%. When I do the math, that tells me that 7 women out of 10,000 will will avoid this fate.
For each of them, anywhere from 2 to 10 women will be overdiagnosed -- will be diagnosed with a condition that, if left untreated, would never have harmed them. They will undergo surgery, radiation, and/or chemotherapy, which does them no good, and only harms them.
So why does the Komen Foundation lie to women? I'm going to take a guess -- some of their big donors profit from cancer treatment. If they want to argue with me, my e-mail is in the side bar.