Is Susan G. Komen “Overselling” Benefits of Mammography?
I think we can all agree that Susan G. Komen for the Cure has had a rough year. In February, the organization came under fire when news broke that it had dropped Planned Parenthood from its grantees list, a decision that was quickly reversed when the backlash reached a fever pitch. Heads rolled. Higher-ups resigned. It was, well, a PR nightmare.
Now experts are pointing a finger (not the finger, geez) at Komen again, arguing in a paper published on the British Medical Journal’s website today, that the Susan G. Komen foundation has misled women with its advertising promoting mammography.
“Unfortunately, there is a big mismatch between the strength of evidence in support of screening and the strength of Komen’s advocacy for it,” writes authors Steven Woloshin and Lisa M. Schwartz, both professors at the Dartmouth Institute for Health Policy and Clinical Practice at Dartmouth College. “A growing and increasingly accepted body of evidence shows that although screening may reduce a woman’s chance of dying from breast cancer by a small amount, it also causes major harms.”
The authors lobby that Komen “overstates the benefit of mammography and ignores harms altogether,” using “hopelessly biased” statistics to persuade women to get mammograms. An example: In a Komen campaign last year, the organization says women must get screened because “early detection saves lives. The 5-year survival rate for breast cancer when caught early is 98%. When it’s not? 23%.”
The authors say the statistics here are flawed. Actually, they put it a tad more forcefully: “This benefit of mammography looks so big that it is hard to imagine why any woman would forgo screening. She’d have to be crazy. But it’s the statistical advertisement that’s crazy.” Ouch.
The reason has to do with when five-year survival rates are calculated—from the time cancer is diagnosed. While a mammogram might diagnose cancer earlier than a touch-and-feel exam (because smaller tumors that can’t be felt to the touch might be discovered), the five-year survival rate may be artificially inflated, simply because the diagnosis time was earlier rather than later.
Consider this for instance, from the paper: “Imagine a group of 100 women who received diagnoses of breast cancer because they felt a breast lump at age 67, all of whom die at age 70. Five year survival for this group is 0%. Now imagine the women were screened, given their diagnosis three years earlier, at age 64, but still die at age 70. Five year survival is now 100%, even though no one lived a second longer.”
See what they did there? Interesting, right?
Another problem is that mammography leads to overdiagnosis, which also inflates the five-year survival rate. The screening test sometimes finds cancers that “would never have killed—or even caused symptoms during a person’s lifetime.” But those people are counted as survivors, anyway. “Overdiagnosis inflates survival statistics even when screening fails to save lives,” write Woloshin and Schwartz. “The more overdiagnosis that occurs, the greater the inflation.”
What’s more, overdiagnosis—and therefore, mammography—leads to more harm than good, the authors argue, entailing unnecessary rounds of chemotherapy, radiation and surgery. “For every life saved by mammography, around two to 10 women are overdiagnosed,” they write.
So if these screening survival statistics don’t tell the whole story, how should we measure the extent to which early detection measures, such as mammograms, reduce death? The authors say you have to look at randomized trials—which, unfortunately, come with statistics that are far less sexy than those five-year survival rates. For a women in her 50s, for example, screening only helps reduce the risk of death from breast cancer in the next 10 years by .07 percent—from 0.53 percent to 0.46 percent—compared to women who aren’t screened. For women in their 60s, the risk is reduced by only 0.27 percent. And when you consider that early detection might set off a wave of followup tests and treatments, like biopsies and chemotherapy, which might not extend life, the harm suddenly outweighs the good.
That’s not much to write home about—and certainly doesn’t make for appealing ad copy.