If you're a woman who truly cares about her health, why not get a mammogram? "Early and often" is the key to successful detection, right?
Not so, say a pair of Dartmouth researchers in a recent article in the British Medical Journal. They write:
Between 20% and 50% of women screened annually for a decade experience at least one false alarm requiring a biopsy. Most importantly, screening results in overdiagnosis. For every life saved by mammography, around two to 10 women are overdiagnosed. Women who are overdiagnosed cannot benefit from unnecessary chemotherapy, radiation, or surgery. All they do experience is harm.
The breast cancer advocacy group Susan G. Komen for the Cure ignores these risks and uses misleading data in mammogram campaigns, the authors say.
Komen's recent ad campaign featured posters that read, "early detection saves lives. The 5-year survival rate for breast cancer when caught early is 98%. When it’s not? 23%."
Say, for instance, 100 women receive diagnoses of breast cancer at age 67, not through screening but because they detect a breast lump. Assume they all die at age 70; five-year survival for this group would be 0%. Now, say the women were screened and given their cancer diagnosis three years earlier, at age 64, but they still die at age 70. Five-year survival is now 100%, even though no one in the screening group lived any longer.
The article authors say the use of 5-year survival rate stats is "hopelessly biased." It makes sense, for example, that women diagnosed with breast cancer at age 40 would be way more likely to live another five years than a woman diagnosed at 70. That's not good mammograms at work, that's just the statistics of aging.
Early detection can also distort five-year survival rates, Schwartz and Woloshin argue, because it can catch small tumors that would never have caused symptoms or killed patients to begin with; some tumors grow extremely slowly or not at all. By diagnosing these women, you’re including patients who will by definition survive, thereby inflating five-year survival statistics even though the screening itself didn’t actually save lives.
“If there were an Oscar for misleading statistics, using survival statistics to judge the benefit of screening would win a lifetime achievement award hands down,” the authors write.
Why would Komen mislead women about mammograms? I'd guess it's matter of simplifying their message. At this point mammograms are the most accessible method of breast control detection we've got, so to help the most women detect breast cancer in its early stages Komen needs a strong clear agenda. "All women should received mammograms" sounds a lot more digestible and convincing, than, "All women over 50 should get mammograms, but for those under 50 mammograms may do more harm than good, and they might not be that helpful for older women either."
This is the second major controversy for Komen this year, after they temporarily pulled funding for Planned Parenthood screenings.
Photo: Don Kennedy/Flickr