Worse, it's seeing cancers that aren't actually there—called false-positives—which is causing unnecessary stress and worry, and even triggering treatments such as breast removal surgery that
Researchers from the International Prevention Research Institute in Lyon, France are the latest to weigh in with their own damning verdict. Routine mammography, they say, has only "a marginal effect on breast cancer mortality"—in other words, it's not saving many lives—and up to half of the cancers it's seeing are false-positives.1
Their discovery comes at a time when health authorities are beginning to question the wisdom of using mammography as a routine test. They are already exploring different—and hopefully more accurate—technologies.
The Lyon researchers took a close look at the Dutch screening program, which invites women over the age of 50 to have a mammogram every two years, and more recently has extended the program to women aged between 70 and 75.
The program was introduced in 1988, and just seven years later, the rate of breast cancer deaths had started to decline, but a study in 2004 discovered that was true only for larger and more advanced cancers, classified as stages 2 to 4. The early-stage cancers weren't being picked up—and if they were, two out of every three breast cancer deaths could be prevented, other researchers have estimated.
The Lyon researchers discovered a similar trend: the rate of breast cancer deaths in Holland had dropped by 38 percent from 1989 to 2013, and so, on the face of it, mammography could be considered a success. But it wasn't that clear-cut; the decline had started in women under 50 in the 1970s, years before routine mammography was introduced in Holland, and breast cancer was on the increase in women aged 70 and over. In fact, rates of breast cancer deaths were falling in each successive generation, suggesting something else was going on, such as improvements in lifestyle and treatments.
Adding all these other possibilities into the mix, the Lyon researchers estimated that mammography was responsible for, at best, a 5 percent reduction in breast cancer deaths, but other factors, such as better treatments, were accounting for a 28 percent reduction.
It's a small reduction, but possibly worth it—until you then factor in the false-positives that mammography is recording. In women younger than 50, around half of all stage 1 cancers the technology was seeing weren't there, and the false-positive rate got even worse when digital mammography was introduced in 2007. The newer technology's false-positive rate was 56 percent.
For every 640 genuine cases of stage 1 breast cancer that digital mammography correctly identified, 8,859 women were told they had breast cancer when they didn't, the researchers estimate—a ratio of 14 false-positives for every one genuine case.
Comparing the experience in Holland to neighboring countries is also revealing, the Lyon researchers say. Dutch women are dutiful when it comes to their routine mammogram, with 80 percent of those over 50 turning up for their biennial screening. By comparison, just 50 percent of Belgian women do so—and yet the rate of breast cancer deaths has fallen by similar amounts in both countries.
Their discoveries are nothing new; rather, they are another inconvenient reminder of a technology that isn't working. And yet routine mammography was introduced in developed countries in the 1980s with the expectation that it would reduce deaths from breast cancer by a third.
Over the years, researchers have consistently demonstrated that this was a false hope. Four years ago, the Swiss Medical Board took another look at the early research studies that led to the promotion of mammography, and they found a trail of bad science. The studies, which date back to 1963, came to false conclusions, the board researchers discovered, and, just as the Lyon team concluded, the cons outweighed the pros. Mammography was seeing more false-positives than real cases; in fact, for every few cases it was identifying, it was coming up with a hundred false-positives.2
Other researchers think that a manual examination—where a woman checks for lumps—is just as effective. The Canadian Breast Screening Study tracked the health of around 90,000 women aged between 40 and 59, half of whom were having regular mammograms and the rest checking for lumps. During the study, 3,250 women in the mammography group had breast cancer diagnosed, compared to 3,133 in the physical examination group, and breast cancer deaths in the two groups were 500 and 505 respectively. But of the cancers detected by mammography, 22 percent were false-positives.3
The Cochrane Collaboration—a highly regarded independent research unit that has the ear of government—has little good to say about mammograms.
The Nordic Cochrane Centre in Denmark took another look at eight studies, involving around 600,000 women, and concluded that mammography isn't saving lives.
Although it didn't save any more lives than those who hadn't been screened, many more who had a mammogram had radiotherapy, a lumpectomy or mastectomy, when the breast and surrounding tissue is removed.
The trouble was that most of the procedures were unnecessary, the Cochrane researchers found, because of the high level of false-positives; for every genuine case, 10 women had a
false-positive reading that resulted in invasive treatments.4
When it comes to mammography, two worlds seem to co-exist. One constantly reports that mammography is a failed technology that produces 10 times the rate of false-positives to genuine cases, and the other is healthcare's public face, which refuses to accept the evidence and instead continues to assure women that it is an essential safeguard against breast cancer.
The latter's argument is, in part, driven by emotion, as the Swiss researchers discovered when they presented their report. They were accused of being unethical, irresponsible and even adding to the breast cancer death toll.
But as one of the researchers said later: "From an ethical perspective, a public health program that does not clearly produce more benefits than harms is hard to justify."
Too soon, too early
The start of routine mammogram screening can begin at 40 if you're an American, and 50 if you live in the UK. But both are still too early, says the American Cancer Society (ACS), which, instead, feels that regular screening could be delayed until a woman is 45, and it still wouldn't make any difference to survival rates. By the time a woman reaches the age of 55, routine screening could be reduced to once every two years.
This is because of mammography's low detection rates, coupled with the high level of false-positives, which put a woman through a great deal of unnecessary stress and worry, and even costly treatment.
Even an august body like the ACS says that manual checking is reliable if a woman has only a low risk of breast cancer, although those with an 'average' and higher risk should still have a mammogram, they say.
Perhaps mammography should be restricted to women with a family history of breast cancer or who are at higher risk because of their genetic profile; for them, starting regular screening at the age of 40 makes more sense.
Why so many false-positives?
Most false-positives are cases of DCIS (ductal carcinoma in situ), which, despite the name, rarely develops into cancer. Of the 60,000 new cases of DCIS detected in the US every year, just 3,000 cases—less than 5 percent—ever evolve into full-blown cancer, and 98 percent of women diagnosed with DCIS are still healthy and well 10 years later.
DCIS is a pre-cancerous condition where cells in the milk ducts behave abnormally. It's not cancer, however—DCIS is graded as stage 0, or 'non-cancerous'—and the activity remains in the duct and doesn't spread to breast tissue.
What's a mammogram?
A mammogram is a low-energy X-ray that uses ionizing radiation to create an image of the breast. It can be uncomfortable, and even painful, for the women having the procedure because the breast needs to be compressed between two plates.
If there is already cancer in the breast, the procedure can help spread it further, critics have said.
Mammography is designed to see mass and structure, but a radiologist who is trained to interpret the images cannot tell whether a lump is cancerous or aggressive.
That's because a mammogram cannot detect activity, which means it often misses fast-growing tumors, which are the ones most likely to be fatal.
Mammograms also miss cancers when the breast tissue is dense, which is more common in younger, pre-menopausal women, and in women taking hormone replacement therapy.
It's such a failing that Congress even passed a special bill that requires radiologists to explain the limitations of the procedure to women who have dense breast tissue and offer them an alternative screening technology, such as ultrasound.