What the Task Force is saying is simply this – On a population basis, the net gain from adding 10 years of mammography in all women is small in relation to the risks of over-diagnosis, over treatment, unnecessary biopsies and anxiety. But you, as a patient, in consult with your physician and assessing your own personal risks of breast cancer, may decide you want to get a mammogram anyway.
What they meant to do was to take mammography out of the realm of the knee-jerk, automatic and into the realm of informed decision making. They meant to inform women that mammography’s 15% or so reduction in mortality comes at a price – a price that is physical, emotional and financial, in the form of false positive results, unnecessary biopsies and the anxiety and dollar cost that accompanies them. They also meant to dispel popular overblown notions about what mammograms actually do by clarifying both their benefits and their risks, so that women are making the most informed decision they can about whether or not to have this potentially lifesaving test.
The task force members should have anticipated that the timing of their recommendations coincident with health care reform would lead to misunderstanding about their role. Their cluelessness in this regard alone should be proof that they have no ties with the stakeholders in health care reform, who clearly would have managed the spin upfront.
Which is not to say that the task force’s recommendations won’t be used to guide policy decisions, which is why everyone is taking this all so seriously.
What you need to know about mammograms
The lay public has an almost magical thinking about what mammograms actually do. This is not surprising given the intensity with which we have been advising them to have mammograms over the years. So it is not unexpected that women have been taken aback by the hard reality about mammograms that they are now being asked to accept. That said, here’s what you need to know -
1. Mammograms don’t prevent cancer. They diagnose it. It’s a simple but important distinction that gets clouded by the magical thinking surrounding this screening test. The value of mammography lies in its potential to diagnose cancers at an earlier stage, allowing life-saving treatment to begin earlier.
2.Because they use radiation, mammograms can actually cause cancers. Though a single mammogram has a low risk in this regard, the radiation exposure from annual mammograms over many years adds up. The task force estimated that on a population basis, annual mammograms from age 40-50 would induce 8 breast cancers for every 100,000 women.
3. Mammograms are not a perfect test. In general, they miss about 10% of cancers, more if you have dense breasts, which are more common in women under age 50. In addition, mammograms have a high false positive rate, meaning that if you have an abnormal mammogram, the odds are high that your biopsy will be benign, and technically unnecessary.
The task force estimated that the cumulative risk for a false-positive mammogram with 10 years of annual screening was about 50%. The younger you are, the higher the chance your abnormal mammogram will be a false alarm. The higher your risk of breast cancer going into screening, the lower your risk of a false positive result.
4. Mammograms may be better at diagnosing slower-growing cancers than more aggressive tumors. Think about it. If a tumor is growing slowly, testing once a year will find it sooner rather than later. If it’s a fast growing, aggressive tumor that spreads out of the breast at a smaller size, a test that is done only once a year may not pick it up before it has spread beyond the breast. So we may be finding and over-treating tumors that may never cause much problem, while missing the bad players. (I myself have a harder time accepting this as an argument for cutting back on screening in women under age 50 than for women over age 70.)
In this regard, one of the most problematic diagnoses made by mammography is that of DCIS, or ductal carcinoma in situ, a non-invasive neoplastic growth that looks like breast cancer by has not invaded beyond the duct wall, and may never become invasive. Mammograms are really good at finding DCIS, since its hallmark is calcifications, which tend to show up pretty well even in dense breasts. So we end up treating and even performing a lot of mastectomies because of DCIS, without knowing if we are impacting mortality.
Finally, if mammograms were as good as everyone thinks they are, then we should expect over the years to find less and less advanced breast cancers, since we should be picking them up earlier and treating them. Unfortunately, this has not yet been proven.<
5. Mammograms are a better screening tool in older versus younger women. In women ages 40-49, 1900 mammograms must be performed to prevent a single death in this age group, compared with 1339 women age 50-60, and 377 women age 60-69. This is because breast cancer risk increases with age (meaning a positive result is more likely to be a true positive) and because older women have less dense breasts, so that there are less false negative mammograms.
Measuring mammogram success by years of life saved instead of mortality alone, mammograms starting at age 40 look better as a screening tool, but still perform better in women over age 50.
6. The benefit of annual vs. biennial mammograms is negligible. Meaning you can go every other year without sacrificing much in the way of benefit (about 1-2% absolute risk reduction benefit), and save additional radiation exposure.
7. Despite their imperfections, Mammograms save lives. To the tune of about a 15-20% reduction in women ages 40-49, the group most affected by the new recommendations. This is an important fact that, in my opinion, keeps getting lost in the discussion about the guidelines.
Which brings me to the elephant in the room.
The Elephant in the Room
Breast cancer causes about 4,500 deaths annually in women ages 40-49, and is one of the leading causes of death in women in this age group. (This data does not include cancer deaths occurring after age 49 in women diagnosed in these years.) In the 10 year interval between 40 and 49, then, about 45,000 lives are lost to breast cancer. That’s no small number, and it’s why breast cancer advocates are up in arms at the recommendations.
Which brings me to the real crux of the question – how many of these breast cancer deaths is mammogram preventing in women ages 40-49? Put another way, if you forgo mammograms in that age group, what are your odds of dying as a result of that choice?<
A age 40, what are your odds of dying in the next 10 years from breast cancer?]
This was not an easy number to find. SEER data on cancer mortality groups ages from 35-44, 45-55 and so on, so it’s taken me a long time to find the data. But I finally found it.
At age 40, your chance of developing breast cancer in the next 10 years is 1.44% or about 1 in 69. Your chance of dying from breast cancer in that interval is about 1 in 480. (This compares to a risk of about 1 in 280 for a woman at age 50, 1 in 146 for a woman at age 60, and 1 in 108 at age 70, and so on.) Here’s how that risk looks visually, in the thousand dot graph below, with the red dots representing breast cancer deaths among 1,000 women.
So if mammograms prevent 15% of breast cancer deaths, then if you are 40, and have mammograms for the next 10 years, your chance of dying from breast cancer is reduced from 1 in 480 t0 about 1 in 564.
USA today estimates that annual mammograms reduce the 10 year mortality risk for women ages 40-49 from 1 in 300 to 1 in 357, as compared to women age 50-59 whose risk is reduced from 1 in 112 to 1 in 144.
That’s not a big individual reduction as far as cancer screening goes, especially when one compares it to, say, colon cancer screening, which reduces deaths from colon cancer by as much as 60%.
Looking at the numbers from a population rather than individual standpoint, assuming a US population of about 21 million women age 40-49, routine mammograms in this age group prevents about 680 deaths per year. Is that really worth having 21 million women get an annual test that over 10 years will result in 50% of them having an unnecessary breast biopsy? It certainly does not stand up to the standards we’ve set for screening tests in the past.
But breast cancer advocates will argue that every one of those 680 lives represents someone’s friend, spouse, parent or relative. How can we say those lives aren’t worth saving? But with that kind of argument, we’d be mammogramming 20 year olds. If mammograms were free and perfect, that would be a good argument. But they are neither.
I think when a screening test has such a high potential for false positives and invasive biopsies over time, it makes sense to allow individuals to make their own decisions about that screening. I also believe that breast cancer, because it is a leading cause of death in women age 40-50, deserves to be addressed as a risk, even if it is to decide in an individual to forgo screening.
What if You are High Risk?
The data the task force used to make their recommendations encompassed all women having screening, including both low and high risk women. But what if you are at increased risk?
You can calculate your individual risk for breast cancer by using one of several risk assessment tools – the most commonly used one being the Gail Model. The Gail model can give you your individual risk of being diagnosed with breast cancer in the next 5 years. You can then us this number to discuss with your doctor whether or not you want to start mammograms before age 50. I don’t know that the model can be used to predict mortality reduction from mammography in high risk women, but would say that if your risk for breast cancer approaches that of a 50 year old woman, you should start routine screening mammograms.
An important high risk group not addressed by the guidelines are African American women, who in general are diagnosed at more advanced stages of breast cancer and have higher breast cancer mortality rates than Caucasian women. Given that much of the data being used to support the USPSTF guidelines come from Scandinavian countries, one must question their application to non-white populations, including Hispanic and Asian women. Fortunately, the Gail model does include ethnicity in its risk calculation.
Bottom Line
Mammograms in women under age 50 are less efficient than in women over age 50, and come at a higher cost in terms of over-diagnosis and potential over-treatment. The USPSTF made a decision that the cost differential was enough to recommend against knee-jerk, routine mammograms in all women under age 50, and instead recommend that women discuss the decision with their doctor before deciding to start screening.
The American Cancer Society, the American College of Obstetricians and Gynecologists and the American College of Radiology continue to recommend routine mammogram screening every 1-2 years starting at age 40.
What do I recommend?
I’ve addressed this issue before, and have not changed my practice, which at this point is to offer mammograms starting at age 40 in all my patients. However, I am now framing it as an option rather than an undebatable recommendation for my low risk patients, which means we spending more time discussing the issue before I place the order.
So far, when presented with the data, every one of my low-risk patients age 40-50 has decided to have their mammograms. However, more than a few made that decision only after confirming that their insurer would continue to pay for the test. I’ve queried a few as to how much they would pay to have that mammogram if their insurer declined to pay – about $200 seems to be the break point above which those few low risk patients would decline the test based on cost alone. Most women are either willing to pay or fight for payment whatever the cost. (This is by no means a scientific sample, but I think captures the gestalt in my practice, which happens to include a fair number of high risk women.) In the absence of any other screening, most women seemed willing to accept the high rate of biopsy in return for a mortality reduction, however small.
I also frequently order screening sonograms in high risk women with dense breasts, and MRI in women with a first degree relative with premenopausal breast cancer or other risk factors for whom this testing has been recommended.
I am comfortable spacing mammogram screening to every other year, especially since that’s about the frequency many of my patients end up getting them anyway. The task force recommendations have certainly made me more comfortable reassuring the patient who calls a few weeks before her annual mammo is due and can’t be fit into the radiologist schedule for several months.
I have to admit I have some concerns about my risks if and when a patient declines routine mammograms. Will I get sued if I don’t urge her to get a routine mammogram and she ends up with an advanced stage breast cancer at some point in the future? Should I have her sign something to protect myself? What is the minimum I need to document to cover my tail? I’m also wondering how long it will be before the first lawsuit against a doc who follows the taskforce guidelines is filed. Will they try to sue the taskforce members themselves? (I wouldn’t put it past some of the lawyers.)
A Call for a Decision Tool
The Australian Screening Mammogram Decision Trial has a wonderful web-based tool to assist women age 40 in making a decision about mammography. I’d like to see the USPSTF develop a similar tool for American women incorporating the latest data they used. It’s the least they can do to help American women and their physicians begin to incorporate their recommendations into practice.
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Recommended reading
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Note – I clarified morality statistics from a previous version of this post, and apologize if they appeared misleading. They were technically correct, but I think this is clearer. Looking at deaths in this age group overall, cancers as a group account for about 30% of deaths, and breast cancer a third of these, or 10% of deaths overall. Heart disease as a group accounts for about 20% of deaths, with heart attacks about 5% of deaths overall.
A well-written and balanced article on mammography from USA Today may help move the conversation about this screening test away from hype and a bit closer to reality. The title – “Mammogram is ‘terribly imperfect’, though recommended.”
Mammographic density is a measure of permeability of x-ray, and an indirect measure of the density of breast tissue. Increased breast density is an independent risk factor for breast cancer, but is more likely a marker for 
I practice medicine, cook and wax prolific in New York City. You can call me Peggy. Or Dr P. Just don't call me late for dinner.
