Thirty Years of Breast Cancer Screening May Have Done More Harm Than Good

A recent op-ed in the New York Times by H. Gilbert Welch, a co-author of Overdiagnosis, describes a tragedy of ignorance and overconfidence. The current emphasis on regular mammograms began thirty years ago. They will prevent breast cancer, doctors and health experts told hundreds of millions of women. They will allow early detection of cancers that, if not caught early, would become life-threatening. The campaign was very successful. According to the paper cited by Welch, about 70% of American women report getting such screening.

It is now abundantly clear this was a mistake. If screening worked perfectly — if all of the cancers it detected were dangerous — the rate of late-stage breast cancer should have gone down by the amount that the rate of early-stage breast cancer went up. Over the thirty years of screening, the rate of (detected) early-stage breast cancers among women over 40 doubled, no doubt because of  screening. (Over the same period the rate of early-stage breast cancers among women under 40 barely changed.) In spite of all this early detection and treatment, the rate of late-stage breast cancer among women over 40 stayed essentially the same. All that screening (billions of mammograms), all that chemo and surgery and radiation, all that worry and time and misery — and no clear benefit to the women screened and those who paid for the screening, treatment, and so on. Roughly all of the “cancers” detected by screening and then, at great cost, removed, aren’t dangerous, it turns out.

Quite apart from the staggering size of the mistake and the long time needed to notice it, screening has been promoted with specious logic.

Proponents have used the most misleading screening statistic there is: survival rates. A recent Komen Foundation campaign typifies the approach: “Early detection saves lives. The five-year survival rate for breast cancer when caught early is 98 percent. When it’s not? It decreases to 23 percent.” Survival rates always go up with early diagnosis: people who get a diagnosis earlier in life will live longer with their diagnosis, even if it doesn’t change their time of death by one iota.

Did those making the 98% vs. 23% argument not understand this?

I applaud Welch’s research, but his op-ed has gaps. A unbiased assessment of breast cancer screening would include not only the (lack of) benefits but also the (full) costs. Treatment for a harmless “cancer” may cause worse health than no treatment. Maybe chemotherapy and radiation and surgery increase other cancers, for example. What about the effect of all those mammograms on overall cancer rate? Welch fails to consider this.

Welch also fails to make the most basic and important point of all. To reduce breast cancer, it would be a good idea to learn what environmental factors cause it. (For example, maybe poor sleep causes breast cancer.) Then it could be actually prevented. Much more cheaply and effectively.  Yet the Komen Foundation and the Canadian Breast Cancer Foundation say “race for the cure” instead of trying to improve prevention.


20 Replies to “Thirty Years of Breast Cancer Screening May Have Done More Harm Than Good”

  1. Trying to get my head around this phrase ‘harmless cancer’. What cancer would that be?

    Seth: Almost all of them, apparently, when it comes to early-stage breast cancers.

  2. Even with articles like this, the medical industry will not change their guidelines. Mammography (and the attendant procedures, drugs, etc.) simply makes too much money!

    I would also like researchers to look at that other sacred cow: colonoscopy. I have never seen anything about the numbers needed to treat or the harm that can be done with this procedure…

  3. Research into cancer prevention is worth pursuing, but so is the development of reliable screening tools. I think few would dispute that when cancer is detected and treated early – before metastasis – lives are saved. That’s why Welch’s findings are so surprising.

    What I get out of the op-ed isn’t that cancer screening is useless, but that for some reason mammography is a poor screening tool. Maybe breast tumors that eventually advance to late-stage cancer grow so quickly that a biennial mammography is unlikely to catch them in time. Or maybe it’s a mistake to focus on gray and white blotches on a mammogram; we should be looking at biochemical blood markers instead. In any case, early detection should still be a major emphasis in cancer research.

    Seth: The op-ed makes me think the whole thing should be investigated: how did such a big mistake come to happen? Was evidence ignored? Misleading? Or what?

  4. LemmusLemmus wrote: Another – albeit nonfinancial – cost of positive screening results is that people worry, and quite a bit.

    They’re not too happy with having their breasts hacked off for no reason, either.

  5. LemmusLemmus: recall the anecdote in the Gigerenzer book of the German doctor who committed suicide upon learning that mammograms only had a ~10% chance of having cancer. He had recommended a mastectomy to anyone who screened positive.

  6. If you take your well-running car to some auto repair chains for a free diagnosis, you can count on getting a report that says your car needs $500 worth of repairs.

    If you feel fine and go to some doctors for a checkup, you can count on getting lots of prescriptions for addictive junk.

    At least the car shop won’t turn you into a crazed drug addict.

    Skip the doctor, and just get an oil change and a car wash.

  7. It’s far worse than just unnecessary worry and unnecessary mastectomies.

    Tamoxifen is often prescribed for breast cancer (and for pre-cancerous masses that get picked up on mammograms). The side effects of Tamoxifen include endometrial (uterine) cancer.

    In other words, current screening and treatment practices are actually, literally causing cancer in previously cancer-free patients.

  8. Remember Gigerenzer’s point that German oncologists recommend breast screening for their patients but not for their wives or themselves.

  9. The above article and some of the comments are about as relevant as those who have never had a sexual experience but feel qualified to write and comment about sex. My qualifications to discuss the subject of screening are that I have been involved in breast cancer screening and surgical operations for over 40 years.
    Money was not the motivation. Decreasing true misery was the motivation.
    First you must accept that people do get breast cancer. There may be differing levels of aggressiveness but you cannot always define the level as easily as may be thought. Most of you were not present when we did “radical mastectomies” requiring multiple blood transfusions as the only treatment. Most of you were not there when such patients frequently required post operative psychiatric care. Most of you were not there when radiation was primitive and we did not even have good chemo. So yes, there is waste, false positives, anxiety and increased cost. All of it worth it when 80% + of the patients can have lumpectomies and save their breasts, require less psychiatric care, and have better qualities of life. Don’t throw out the baby with the wash. Refine the indications and frequency required for screening mammography. Perhaps every 2 or 3 years rather than annually. Find ways to reduce cost by having technicians read films rather than radiologists and only have radiologists for more difficult situations. The cynicism and false expertise noted above are offensive to those of us who have been on the front lines, seen the worst and are truly happy for the not-so-perfect improvements that we currently have.

    Seth: What is the evidence that screening mammograms have done more good (you call them “improvement”) than harm? I don’t see it. When you say that screening mammograms “save their breasts” you fail to understand the study that Welch describes. It concluded that essentially all of the “cancers” detected by screening mammograms do not endanger breasts.

  10. Once again, there doesn’t seem to be any discussion of the cost of the mammography program. Why is no one ever willing to mention the vast sums of money wasted on so-called “preventive” medicine instead of encouraging people to see a physician only when they are troubled by an actual symptom?

  11. Seth Roberts wrote: What is the evidence that screening mammograms have done more good (you call them “improvement”) than harm? I don’t see it. When you say that screening mammograms “save their breasts” you fail to understand the study that Welch describes. It concluded that essentially all of the “cancers” detected by screening mammograms do not endanger breasts.

    Michael Eades wrote an interesting post on his Protein Power blog a year or so ago where he talked about the surprising fact that (in his opinion( virtually no physicians are competent to read scientific papers, even in their fields. In Eades’ opinion, what they can understand is “Case Reports” — basically chronological stories of an individual patient’s experience.

    That said, the fact that they don’t know how to read a study doesn’t mean that they don’t think they already know everything in it. 🙂

    Seth: That understates it. Dr. Seltzer failed to understand an op-ed in the New York Times about his own area of expertise.

  12. ACR/SBI: Bleyer and Welch Breast Cancer Screening Article in NEJM Deeply Flawed and Misleading

    The article by Bleyer and Welch[1] in the New England Journal of Medicine, which suggests that screening mammography finds many cancers that would not advance to kill patients, is based on false assumptions. The thesis depends on their suggestion that the incidence of breast cancer is much higher than would have been expected had screening not been initiated.

    The authors suggest that the baseline incidence of breast cancer would have increased by 0.5percent each year, when in fact, the data show that it would likely have increased by twice that amount. The incidence of invasive breast cancer has actually increased by 1percent per year for decades.[2] In 1940, it was 60/100,000. By 1980, prior to any screening, it had risen to 100/100,000. If there had been no screening, and the rate had continued to increase as it had for 40 years, the incidence in 2008 would have been over 130/100,000. In fact, due to prevalence screening, where new women who have never been screened enter the screened population each year, and lead time (cancers found earlier due to screening), the incidence of breast cancer, without any “overdiagnosis” would have been expected to be even higher than 130/100,000. In reality, it was lower even than that, at 127/100,000.

    Therefore, not only is there no evidence of the authors’ claimed “overdiagnosis,” but it is likely that treatment of ductal carcinoma in situ (DCIS) over the past decades has reduced the incidence of invasive cancers. This is in addition to the observed 30 percent reduction in deaths each year due largely to screening. While the authors observe that screening is associated with a reduction in advanced stage cancers, they fail to recognize the fact that a reduction in advanced stage disease is not required to have a reduction in deaths from screening. Staging is a crude effort to group cancers for purposes of trying to understand how they respond to therapy. Unfortunately, there are deaths from breast cancer among women with all stages of these malignancies, even the very earliest, DCIS.

    The thesis by Bleyer and Welch is simply wrong. Misleading articles, based on faulty assumptions and methodology are counterproductive. If such misinformation is used to determine screening guidelines and recommendations, the cost may be lost lives.

    Seth: Thanks. This can be found at

    It would be more interesting if (a) it was attributed to someone and (b) it didn’t make a big mistake in the very beginning. Bleyer and Welch did not suggest that “the incidence of breast cancer is much higher than would have been expected had screening not been initiated”– that is, that screening increased breast cancer. They concluded that screening did not lower the rate of life-threatening breast cancer. The stuff about the incidence of breast cancer is irrelevant. No one says that screening is supposed to change the rate of breast cancer — it just detects some breast cancers earlier than they would otherwise be caught.

  13. I’m having a hard time grasping your take on the 98% vs 23% issue – could you spend a few words on that?

    Seth: If a disease is detected earlier it will be survived longer, even if nothing else changes. Even if it is not treated. Breast cancer left untreated would be survived longer if it were detected earlier. So the mere fact of better five-year survival does nothing to support screening campaigns. Reasonable comparisons were available: age-equalized rates of dying of breast cancer for women who are and are not screened, for example. Results of experiments, even better. Yet the proponents of screening chose a grossly misleading comparison. Why?

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