"Annual mammograms may reduce risk of mastectomies for women in their 40s,” a headline in the Los Angeles Times teases.
The article refers to a study performed by Nicholas M. Perry and his colleagues at the London Breast Institute of the Princess Grace Hospital. According to a press release by the Radiological Society of North America, they found that annual screening mammography reduces the risk of mastectomy in women under 50.
These results come at a propitious time for the manufacturers of the X-ray machines used in screening mammography. In the past couple of years, grave doubt has been cast on the dogma that screening women for breast cancer saves lives. A meta-analysis by the respected Cochrane Collaboration found that annual screening mammography for women aged 50-69 was correlated with a one in two thousand reduction in the risk of dying of breast cancer. Now, if you think such a tiny reduction in risk can even be measured reliably, well, bully for you, but the only statistic that means anything to you as an individual is the OVERALL death rate. What difference does it makes if you die of breast cancer, or of something else at the exact same time? We all die of something, be it from breast cancer or a heart attack or a stroke or getting run over by a bus on your way to the mammography clinic. And the same meta-analysis found that women who had annual mammograms and those who did not had EXACTLY THE SAME DEATH RATE.
Last September, a Norwegian study published in the New England Journal of Medicine which controlled for advances in breast cancer treatment found that screening mammography was correlated with an even tinier reduction in risk – on the order of one in two thousand five hundred. The Norwegian study did not look at all-cause mortality.
In plain English, there is no convincing evidence for the oft-repeated mantra, “Early detection saves lives.”
But even if early detection of breast cancer does not save lives, could it result in less-disfiguring surgery than if a woman waited for symptoms appeared? Let’s take a look at what the researchers found.
Between the years 2003 through 2009, 393 women under the age of fifty were diagnosed with invasive breast cancer at the London Breast Institute. Of these, 156 completed treatment at the center. Of these, 114 had never been screened for breast cancer, while 16 had had a mammogram within the last year. The Institute’s records showed that 3 (19 percent) of the 16 women who had had a mammogram within the last year subsequently underwent a mastectomy, while 64 (46 percent) of the 140 women who had not been screened did so.
But wait a minute. That NEJM article I linked to above showed that when screening mammography was introduced to Norway, the number of cases of so-called “invasive” breast cancer doubled – and it wasn’t even introduced into all the counties of Norway at once. Unless you believe some mysterious force caused the rate of invasive breast cancer to spike at the exact same time screening mammography was introduced, then you must believe that all, or almost all, the extra cases were “cancers” that never would have bothered the woman until she died of something unrelated. Such cancers pretty much by definition are tiny and slow-growing – precisely the sort which are judged not to require radical surgery. That right there could account for the difference between the two groups of women.
The right way to go about answering this question would be to follow a large cohort of women through their forties, with half of them being subjected to routine screening and the other half not, and comparing the rates of mastectomy in the two groups. It may be that such a study would uncover that screening mammography produced a reduction in the number of mastectomies. But it can't be huge. I should estimate the proportion of women in their forties who get a mastectomy to be on the order of one in 650. Whatever the reduction in risk is, it has to be some fraction of that number.
Or maybe there is no reduction in risk at all. It may even be that screening increases the risk of mastectomy, since women who are screened are more likely to be diagnosed with breast cancer. I don’t know. The point is, the authors of this study don’t know either, and they’re not interested in finding out.
The press release goes on to quote Dr. Perry as follows:
“Regular screening is already proven to lower the chance of women dying from breast cancer. The results of our study support the importance of regular screening in the under-50 age group and confirm that annual mammography improves the chances of breast conservation should breast cancer develop.”
The press release did not mention how much of Dr. Perry’s salary is paid for by the manufacturers of the X-ray machines used in mammography, but never mind that for now. I notice the good doctor is choosing his words very carefully. He says that screening is proven to lower the chance of women dying from breast cancer. He isn’t even promising that screening mammography will extend any woman’s time on this earth.
This isn’t about saving lives. It isn’t even about saving breasts. It’s about a Medical-Industrial Complex which is Hell-bent on foisting upon women (and men) as many expensive and invasive interventions as the traffic will bear.
All photos via Wikimedia Commons
ADDENDUM: I was unable to find any data on the prevalence of mastectomies for women ages 40-49. So how did I come up with that estimate of one in 650? Well, according to the National Cancer Institute, 35% of women (all ages) diagnosed with invasive breast cancer have a mastectomy. Elsewhere on their website, they report that the annual incidence of invasive breast cancer in women under the age of 50 is 44 per 100,000, or 0.00044. Let’s assume that every one of those cases were in women ages 40-49. Let’s also assume that the mastectomy rate for this age group is the same as for women of all ages. Then 35% of 0.00044 is 0.000154, or one in 6,500 per year. Multiply that by ten years, and you get one in 650. Whatever the reduction in risk afforded by screening is, it has to be some fraction of this figure.