breast cancer screening: whom to believe?

In 2012 alone there were 24 articles published in different medical journals debating the value of breast cancer screening. The United States Preventive Services Task Force, which despite its name is not a Federal agency but an independent panel of experts that makes healthcare recommendations, changed its screening guidelines in 2009 to recommend against routine mammograms for women in their forties who are not at high risk, and now recommends that women begin biennial mammogram screening at age 50. A group called The National Committee for Quality Assurance, which is an independent non-profit organization that produces guidelines followed by Medicare, Medicaid and many insurance plans, just changed its recommendations for 2014 to align with the USPSTF. Meanwhile we have the Old Guard represented by the National Cancer Institute and the American Cancer Institute, both of which still recommend a yearly or biennial mammogram for women ages 40 and up.

A study from February in the Journal of the American Medical Association shows that the incidence of breast cancer in women ages 25 to 39 is steadily increasing and has been since 1976, without an analogous increase in other age groups. The rate of increasing incidence of distant disease is inversely proportional to age at time of diagnosis. We don’t know why this is happening but the trajectory of this trend predicts an increasing number of young women will present with metastatic breast cancer.

So what’s the screening recommendation for this age group? Well, the American Cancer Institute says that women in their 20’s and 30’s should have a clinical breast exam every three years. So that’s easy, right? At least someone is addressing this age group and maybe the recommendations will change but it’s a start. However, the USPSTF says there is insufficient evidence to support this practice and therefore does not recommend clinical breast examination.National Cancer Institute website re: clinical breast examination says “Clinical breast examination (CBE) has not been tested independently; it was used in conjunction with mammography in one Canadian trial, and was the comparator modality versus mammography in another trial. Thus, it is not possible to assess the efficacy of CBE as a screening modality when it is used alone versus usual care (no screening activity).” However they don’t come out and say don’t do it.

I thought well this could not possibly be true and I am going to find some randomized controlled studies that show the effectiveness of clinical breast exams in younger women. But instead I found an article in the Journal of General Internal Medicine from February that says the same thing, only that CBE should NOT be abandoned because it has been shown to have a benefit in conjunction with mammogram.

The American Cancer Society says women in their 20’s and 30’s should have a clinical breast exam every three years and also recommends breast self-examination, which has been studied but has been found but has been shown not to decrease mortality at all. The rationale is that self-examination increases awareness and that women can have their technique assessed by a professional to make sure they’re doing it right, but that it is also okay not to perform self-examination. They say that women over 40 should have CBE every year.

Now, why is there controversy about mammograms, which have been studied? The controversy exists in large part because of the risk of overdiagnosis, which is when a cancer is found and treated that would not have caused any problem If left undiagnosed and untreated. Overdiagnosis is hard to study because we don’t know when it has occurred, and randomized controlled studies are hard to come by. Also, there might be some doubt as to whether data from studies done decades ago are still applicable. A Panel in the UK led by a Professor Marmot independently reviewed randomized controlled trials and found that for women in the UK, who are invited to screening every three years from ages 50 to 70, some overdiagnosis does occur. Nineteen percent of breast cancers diagnosed in these women would never have caused a problem if left undetected. They also said that since data is so scarce and unreliable in this area, more research is needed. But given that mammograms were shown to benefit women by providing a 20 percent reduction in mortality for those invited to participate in a 20 year screening program, the Marmot Panel strongly backs screening mammograms for this age group. Another study looked at a randomized controlled trial of women in the UK aged 40-49 and found that overdiagnosis in this group was small, between 0.3% and 2.2%.

National Cancer Institute also warns about radiation-induced breast cancer, especially in patients who have mammograms under the age of 30. However the American Cancer Society states that the level of radiation used in modern mammograms does not significantly increase the risk for breast cancer. I didn’t have a chance to examine which claim is correct but clearly you could spend your entire career on this problem.

And finally, whom do we believe? The American College of Obstetricians and Gynecologists changed their minds the other way in 2011, from yearly mammogram starting at age 50 to yearly mammogram starting at age 40, because for women ages 40-49 have window to detect tumors before they become symptomatic is shorter, on average, than for older women. I would err on the side of caution since it is such a point of contention and be more worried about leaving a cancer undetected than about overdiagnosis. Hopefully we all have doctors we trust, doctors who stay up on current research. But it might boil down to, what does your insurance pay for?

Not only is there a fair amount of disagreement among experts, there is also a ton of misinformation out there for laypeople. So we might not know whether to listen to the USPSTF versus the American Cancer Institute, but I can state with certainty that we can’t listen to The Telegraph, Time magazine, editorials about editorials about studies, or any number of well-meaning but totally misleading blogs on this topic, all of which in their attempt to make the subject user-friendly have ended up giving out some potentially dangerous misrepresentations of the truth.

Categories: breast cancer screening

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