Apr 27 , 2022
For every life saved by mammography, as many as two to ten women are overdiagnosed and unnecessarily turned into breast cancer patients with all of the attendant harms of chemo, radiation, or surgery, without the benefits.
What was the impact of the 2009 shift in recommendations by the U.S. Preventive Services Task Force (USPSTF) to delay routine mammography screening until age 50? Ironically, rates of women in their 40s getting mammograms may have actually increased. The thought is that all of the media attention surrounding the change in recommendations may have just reminded women about mammography screening, which underscores the need to better translate evidence into practice.
The new USPSTF recommendations bring the United States closer to European standards, which recommend mammograms every few years starting at age 50. In 2015, the American Cancer Society (ACS) split the difference and, as you can see at 0:36 in my video Do Mammograms Save Lives?, recommended annual mammography screening starting at age 45 and then switching to every other year at 55. ACS suggested this would decrease the lifetime risk of dying from breast cancer from 2.7 percent to less than 2 percent, based in part on a systematic review performed by the Cochrane Collaboration, a highly-respected bastion of evidence-based medicine. But, the authors of the Cochrane review reported that the American Cancer Society had used the wrong number. If you look at the studies their review considered to be “adequately randomized,” they said, there did not appear to be any significant mortality benefit from mammograms at all. What’s more, they asserted that the “available data certainly do not support the popular idea that [breast cancer] screening saves lives. The ACS is a political organization with financial ties to companies with interests in the multi-billion dollar breast-cancer-mammogram industry.”
The Cochrane review concluded: “The studies which provided the most reliable information showed that screening did not reduce breast cancer mortality.” If that’s true, that changes everything. “We believe that the time has come to re-assess whether universal mammography screening should be recommended for any age group.”
And that is exactly what the Swiss Medical Board did. Explaining their position, they said: “We were struck by how non obvious it was that the benefits of mammography screening outweighed the harms…It’s easy to promote mammography screening if the majority of women believe that it prevents or reduces the risk of getting breast cancer and saves many lives through early detection of aggressive tumors. Unfortunately, they are not, and we believe that women need to be told so. From an ethical perspective, a public health program that does not clearly produce more benefits than harms is hard to justify.”
Not surprisingly, their “report caused an uproar.” Critics argued that “the report unsettled women, but we wonder how to avoid unsettling women, given the available evidence.”
What did women say when they were asked what they perceived to be the benefits of regular mammogram screening? As you can see at 2:36 in my video, they think it cuts the risk of dying from breast cancer in half, saving the lives of about 1 in 12 women. In reality, however, the numbers are much different. First of all, the risk of dying from breast cancer regardless of screening is less than most women think and the reduction in risk from screening is much less, with about 5 women in 1,000 dying from breast cancer without screening and 4 in 1,000 dying with screening. Doesn’t saving the life of even one woman in a thousand make it all worth it? Imagine if you were a member of that one-in-a-thousand family whose mom was saved. But even that may not be true.
That is, “systematic mammography screening might prevent about one death attributed to breast cancer for every 1000 women screened, [but] there was no evidence to suggest that overall mortality was affected,” meaning no lives are actually saved. There have been ten randomized trials of mammogram screening, and not one has ever shown an overall mortality benefit. How does that make sense? If mammograms prevent one in a thousand women from dying from breast cancer, then the only way no lives are saved is if mammograms somehow led to the deaths of one in a thousand healthy women. But that’s preposterous, right?
Let me introduce the concept of overdiagnosis. The fact is that some of the tiny tumors picked up on mammograms may have never progressed and some might have even disappeared on their own. So, had those tumors not been picked up during screening, the women would have been none the wiser and would have never been affected by them or even known they had them. But, once cancer is detected on a mammogram, you have to treat it, because you don’t know what it’s going to do. And, in the over-diagnosed cases when it would never hurt you, you’re treating the breast cancer unnecessarily.
How common is that, though? “For every life saved by mammography, around two to 10 women are overdiagnosed.” This means they’re turned into breast cancer patients unnecessarily. “Women who are overdiagnosed cannot benefit from unnecessary chemotherapy, radiation, or surgery. All they do experience is harm.” And these harms can include death. Indeed, “with more overdiagnosis comes increased mortality from the harms of radiotherapy and chemotherapy given to healthy women.” Imagine being in the family whose mom was killed in that case.
The concern is that unnecessary radiation treatments may kill as many as are saved, which is why there’s no evidence of net mortality benefit. Radiation treatments to the chest increase the risk of dying from heart disease and lung cancer. Those may be acceptable risks if you actually have breast cancer that would otherwise kill you, but treatments “that are beneficial for real patients can be lethal for healthy overdiagnosed people”—those who never should have been treated in the first place.
Even if mammograms don’t save your life, might they save your breast? If you catch a tumor early enough, could you avoid a mastectomy? The opposite may be true. The Cochrane researchers explain: “We published the report mainly because we believe it is important for women to know that screening increases their risk of losing a breast.”
“Mammography screening has been promoted to the public with three simple promises that all appear to be wrong…Screening does not seem to make the women live longer…” Instead, it may unnecessarily “increase mastectomies; and cancers are not caught early, they are caught very late.” It may take decades for a tumor to grow large enough to be picked up on a mammogram. And, even when they are picked up, they may not grow any further, which is why we’re concerned “they are also caught in too great numbers. There is so much overdiagnosis “that if a woman really doesn’t want to become a breast cancer patient, perhaps she should “avoid going to screening” altogether. But, if you have breast cancer, don’t you want to know?
“The small probability that a woman may avoid a breast cancer death must be weighed against the more likely scenario that she may have a false-positive result and possible unnecessary follow up testing (including invasive testing); a false-negative result, with false reassurance or delayed diagnosis; or most critically, diagnosis and treatment of cancer that would otherwise not have threatened her health or even come to her attention.”
- Despite the U.S. Preventive Services Task Force’s (USPSTF’s) expert panel’s recommendation to delay routine mammography screening until age 50, there may have been an increase in the rates of women in their 40s getting mammograms, likely due to the media attention paid to the shift in guidance.
- European standards recommend mammograms every few years from age 50, and the American Cancer Society (ACS) recommends annual screening from age 45 and switching to every other year from age 55.
- The Cochrane Collaboration, a highly-respected bastion of evidence-based medicine, determined there did not appear to be any significant mortality benefit from mammograms, asserted that the “available data certainly do not support the popular idea that [breast cancer] screening saves lives,” and concluded that “the time has come to re-assess whether universal mammography screening should be recommended for any age group.” It also identified the ACS as a political organization with financial conflicts of interest, as it has ties to companies associated with the multibillion-dollar mammogram industry.
- Perceived benefits of regular mammography include halving the risk of dying from breast cancer, which may save the lives of about 1 in 12 women. In reality, risk of dying from breast cancer regardless of screening is less than most women think and the reduction in riskfrom screening is much less, with about 5 women in 1,000 dying from breast cancer without screening and 4 in 1,000 dying with screening.
- For every life saved by mammography, as many as two to ten women are overdiagnosed and unnecessarily turned into breast cancer patients, introducing all of the attendant harms of chemotherapy, radiation, or surgery, without the benefits.
- Unnecessary radiation treatments may kill as many as are saved, and radiation treatments to the chest increase risk of dying from heart disease and lung cancer.
- The Cochrane Collaboration review: “The small probability that a woman may avoid a breast cancer death must be weighed against the more likely scenario that she may have a false-positive result and possible unnecessary follow up testing (including invasive testing); a false-negative result, with false reassurance or delayed diagnosis; or most critically, diagnosis and treatment of cancer that would otherwise not have threatened her health or even come to her attention.”
Michael Greger, M.D.