How Routine Mammography Screening Leads to Overdiagnosis & Overtreatment

Karuna Jaggar headshotBy Karuna Jaggar, Executive Director

Around 40,000 individual women die of breast cancer each and every year. Sisters. Mothers. Daughters. Spouses. Friends. For each of these women and their loved ones breast cancer is a personal tragedy.

Breast cancer is also a public health crisis and social justice issue. Despite decades of awareness campaigns, breast cancer is the second leading cause of cancer death for women in the U.S. And a woman’s chances of surviving a diagnosis are significantly impacted by her race, as well as socioeconomic status and where she lives.

The mainstream breast cancer movement tells us that if we just make sure that every woman gets a routine mammogram, we can fix this. It tells us fewer women will die if they get mammograms, and that the answer to the unacceptable inequities in survival can be addressed by expanding access to mammograms. But the facts tell a very different story.

After more than 30 years of widespread promotion of routine breast cancer screening for women at average risk, an undeniable body of research shows the significant harms and limited benefits of population-based screening. The truth is that widespread mammography screening has failed to dramatically reduce the number of deaths from breast cancer.

Last week, a new study in the New England Journal of Medicine added to the compelling evidence that for a majority of asymptomatic women at average risk of breast cancer, the harms of screening may outweigh the benefit.

Researchers from Dartmouth College and the National Cancer Institute (NCI), examined data from the Surveillance, Epidemiology, and End Results (SEER) program looked at the size of breast cancer tumors among women age 40 and older. They examined 37 years’ worth of data, dividing into two time periods, before and after widespread adoption of population-based mammography screening.

Researchers compared the proportion of small (less than two centimeters) versus large tumors (two centimeters or larger) that were detected after the introduction of mammography screening. By focusing on the size of the tumor, an important part of determining what stage the cancer is, the researchers tested the theory that if mammography screening is able to catch more small cancers, there should be a reduction in the number of large tumors diagnosed. The underlying assumption is if there are fewer large tumors, there will then be a reduction in deaths from breast cancer.

What they found is that more small breast cancer tumors were detected after the onset of routine mammography screening, but the number of larger tumors did not go down proportionately. There was only a modest reduction in the incidence of large tumors compared with a much larger increase in the incidence of small tumors found through mammography screening. The researchers calculated that 132 out of the 162 tumors detected per 100,000 women were small cancers that were not likely to grow large enough to cause symptoms or death.

Another way of saying this is that four out of five (81%) of the tumors actually represented overdiagnosis, or a diagnosis of breast cancer that would never cause symptoms or lead to death.

A prior study published in the New England Journal of Medicine in 2012 found that women who had mammography screening were just as likely to die as women who didn’t have mammograms. In 2014, the British Medical Journal published the largest mammography study to date, finding that screening average-risk women – before they could feel a lump in their breasts – did not lead to lower breast-cancer death rates for those in their 40s and 50s. The National Cancer Institute came to a similar conclusion in an analysis of multiple mammography studies involving nearly a half-million women: “Screening for breast cancer does not affect overall mortality.” Indeed an editorial in JAMA last year clearly explains that, “85% of women in their 40s and 50s who die of breast cancer would have died regardless of mammography screening.”

While some breast cancers are very aggressive, most are slow growing, taking a decade or more to become detectable. Many of these slowest growing cancers would never become a problem for women and would not be found were it not for the mammogram we are entreated to get.

Overdiagnosis is a side effect of looking for early forms of disease via routine mammography screening programs. Overdiagnosis is not observable in the clinic with individual women; it becomes evident only through large-scale modeling and statistical analysis. Estimates on overdiagnosis of breast cancers found through screening vary widely, from less than 5% to the latest estimate of more than 80%. The Swiss Medical Board in 2014 provided a widely accepted estimate that 21.9% of breast cancers found through mammography screening represent overdiagnosis.

Overdiagnosis, in turn, leads to overtreatment, which is the treatment of clinically insignificant disease, essentially giving too much treatment without benefit to the patient. Treating a cancer that is not life-threatening leads to significant harm for women. Accepting the Swiss Medical Board estimates, that means one in five women who was told she had breast cancer after her mammogram received unnecessary treatment for cancer. The result is that tens of thousands of women in the U.S. each year are treated unnecessarily for breast cancer and undergo surgery, radiation and chemotherapy for tumors that are not and never would be life threatening.

The immediate effects of surgery, radiation, chemotherapy and other systemic therapies are widely known and can include breast removal, pain and scarring, hair loss, nausea, skin burns, etc. Less commonly discussed, many women experience a range of long-term effects that include physical and health harms such as disability, neuropathy, lymphedema, heart disease, infertility, and secondary cancers; financial consequences from medical debt to un- and under-employment; the psychological toll of having been diagnosed with cancer; and other quality of life impacts of treatment such as issues with sexuality, “chemobrain,” and others.

Doctors cannot look at their patients and know which patients did not benefit from treatment–and so they tend to say that every patient is better for treatment. Women cannot know if their life was saved or not – and understandably tend to think that the mammogram that found their cancer saved their life.

That tens of thousands of women are treated for breast cancer may have gone through all of that for nothing is devastating on a personal and societal level. Women who have felt that their mammogram saved their life may suddenly wonder if they were unnecessarily harmed by screening. Doctors who seek to cure are forced to look directly at the harms of treatment they provide. And we all must contend with the fact that the solution we were promised – screening, early and often – is not ending the breast cancer epidemic

The public has been sold a false bill of goods by mainstream cancer charities, which for years have been pushing the simple story that annual mammography screening is the silver bullet to the breast cancer epidemic despite clear and mounting evidence to the contrary. In 2014 the Swiss Medical Board said boldly in the New England Journal of Medicine that mammography screening is “hard to justify”. The mantra “early detection saves lives” seems intuitive but is wrong, and annual screening seems like a good idea–except the evidence shows it just doesn’t do what we need it to. Even the American Cancer Society, which has long focused their approach on screening, last year adopted updated recommendations that acknowledge the balance does not clearly tip either for or against mammography screening for many women. Each woman must weigh the evidence and make her own decisions based on her known risk factors, values and preferences.

Unfortunately, the problem is the premise of “early detection” itself, not only limitations of the tool. Other screening modalities like ultrasound or MRI also bring the very same issues of false positives, false negatives, overdiagnosis, overtreatment, and cannot overcome the failures of current treatments to save lives. Early detection has not lived up to the promise: it has created a population of over-diagnosed breast cancer “survivors” without actually saving significantly more lives. We will never address and end the breast cancer epidemic simply through breast cancer screening, regardless of the screening tool; we need more effective, less toxic treatments that keep women from dying of breast cancer, and we need to prevent breast cancer in the first place.

This entry was posted in BCA News.

8 Responses to How Routine Mammography Screening Leads to Overdiagnosis & Overtreatment

  1. KATE ALEXANDER says:

    Thank you for a great post! Women need to know these facts and not be bullied into useless mammograms and over-treatment.
    In 1993, at age 50, I had my first mammogram. Diagnosed with Stage 1, invasive ductal carcinoma, 1 cm. ER+. Lumpectomy with axillary dissection and removal of 20 plus lymph nodes (barbaric procedure). Suggested protocol of whole breast radiation and 5 years of Tamoxifen. After researching radiation while in the middle of it, I quit. Never took TAM. I researched Tamoxifen also.

    In June of 2016, I found a “lump”, which my primary doc also felt. I had my first mammogram in 23 years. Guess what? The lump I felt was not cancer, but something else. However the mammogram found: 1.5 cm invasive ductal carcinoma, grade 2, ER+, 1 suspicious node found in the same left breast. Tumor was not palpable.

    They were all over me like a wet blanket. Recommendation: mastectomy followed by radiation and aromatose inhibitor. Found a surgeon to do a lumpectomy, without node biopsy (found not suspicious after all). Did 3 weeks of targeted radiation, which the radiation oncologist said, “you don’t have to do this, but the risk of recurrence in 5 years is 10-20%”. Radiation oncologist is the leading expert in targeted breast radiation. I had full confidence in HER. Forunately or unfortunately, the medical oncologist strongly recommended an aromatose inhibitor to be taken for five years. Of course I then researched all the aromatose inhibitors, which were not around in 1993. I had no confidence in his knowledge or stats. I will not be taking any meds with these side effects with very little evidence of improvement of life expectancy or chance of recurrence. Joint pain, arthritis and oesteoporosis are not in my near future. I am an old athlete and still ski, bike & hike almost on a daily basis. I count my lucky stars.
    Most women I know when diagnosed with breast cancer are scared and do exactly what is proposed by the cancer establishment. Because my MO is to research everything (whatever my current interest), I know more. The internet has saved me endless hours in libraries and money buying books.

    Do I think that this recent tumor could have just hung out for a few more years before I really found it ? Who knows?
    I do know that my experience in 2016 was a whole lot better than 1993, because of my knowledge. The tumor board at my hospital was appalled that I went 23 years (age 50 to 73) without a mammogram.

    On another note: Almost 50% of the female members of my Peace Corps group in India (1965-67) have been diagnosed with breast cancer. We have talked about the experimental pesticides being used on rice, in India at the time. We all suspect that these pesticides and those ingested in the following years are a contributing factor; i.e., the cumulative effect of xenoestrogens. One of these women died, not of breast cancer, but of the after/side effects of radiation: Scar tissue on her aortic value. Two have died of breast cancer. The rest of us are still kicking.

    • Irina says:

      While I agree with Kate on most of the issues she mentioned, I suggest that she reconsider taking aromatase inhibitor. My mother was diagnosed at age of 70, had radiation treatment, no chemo, did not tolerate Tamoxifen but with Aromasin had aboslutely no side effects. Unfortunately the treatment was interrupted by the protocol when 10 years after initial diagnosis passed and three years later my mother developed pleural methastasis what most likely would not have happened if Aromasin was not interrupted. She is now treated with fulvestrant and is doing fine.

      • Kate Alexander says:

        I am glad that your mother is now doing well. Thank you for your suggestion to reconsider. We all would like to think that something would not have happened IF ONLY, we had done something else.

  2. Mariam says:

    Thank you for your article.

    I am not a big believer in mammography, as I was a conscientious and got a mammogram regularly and the mammography never detected my breast cancer (my doctor did in an annual exam).

    Besides preventing cancer in the first place, and better treatments (surgery, radiation, and chemotherapy is rough, let me tell you) we still need something in the middle-we need better screening alternatives than we have today. I could get behind that.

  3. Kate Cox says:

    I always appreciate reading BCA’s perspectives on screening. I honestly have mixed feelings about the recent changes to recommendations about screening ages and frequency. Not because screening guidelines affected me at all. I was diagnosed with a high grade triple negative breast cancer when I was 45 and had never had a mammogram. It’s unlikely that my tumor would have been detected on a routine screening, so I don’t feel bad that I didn’t get one. And treatment beat me up pretty bad, including a disabling neuropathy that is unlikely to improve at this point. So, I know how bad treatment can be. I don’t wish unnecessary treatment on anyone.

    So, I’m all for minimizing over-treatment. But I wonder if we’re targeting the right issue? Is it screening that’s the problem, or that we aren’t very good at figuring out which tumors are likely to kill us? “The researchers calculated that 132 out of the 162 tumors detected per 100,000 women were small cancers that were not likely to grow large enough to cause symptoms or death.” Why aren’t we able to figure that out at the time of biopsy? And isn’t that where we should be redirecting a portion of our screening dollars? Because even though I agree in theory that the benefits of screening don’t necessarily outweigh the risks, it also seems like throwing the baby out with the bathwater. If screening does *sometimes* save lives, how do we get better at making those predictions so that we don’t over-treat but also catch deadly cancers before they become advanced?

    But I totally agree that we should be shifting funding priorities toward true prevention and to finding better, safer, less toxic, more effective treatments. That’s where we’ll see the real impact.

  4. Kiwicelt says:

    My mother died of breast cancer yet having done all the research, I quite happily refuse mammograms. I also refuse cervical screening having realised out inaccurate the LBC test is and the horrendous rates of over treatment. I am quite happy persuing health and enjoying life rather than looking for disease.

  5. Kristin A. Farry Ph. D. says:

    The evidence does not indict early screening. It indicts mammography as a substitute for truly effective early screening. We need effective early screening that detects not only the presence of cancer, but its danger of becoming invasive.

    I am speaking as one whose metastasizing tumor was missed by mammography–after the tumor was big enough to feel with my fingers.

  6. Ebee says:

    Thank you for this article. This is something women need to know. We are constantly pressured to have breast and cervical cancer screening without being given both the information and respect to make informed decisions on it.

    I was referred for a breast ultrasound at age 38 for what turned out to be a superficial skin lesion. The imaging center took it upon themselves to start campaigning for me to have a baseline mammogram from the moment I called to make the appointment, to when I was sitting in the exam room, to afterward. I had the feeling that regardless of what the ultrasound actually said, they would be pushing mammography…and I was right. They found absolutely nothing on the ultrasound, and still classified it as BI-RADS 0 and recommended a mammogram. They went so far as to send me a letter saying “something was found” in order to compel me to come in for a mammogram – when the official radiology report found nothing – and called my doctor when I wouldn’t comply. For what it’s worth, my doctor fully supported and agreed with my decision not to have mammograms now or in the future.

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