Moving Beyond the Breast Cancer Screening Debate
Laura Esseman MD, MBA and Margaret E. O'Kane, MHS
Journal of Women's Health
August 14, 2014
To get the best healthcare quality, the best scientific evidence should inform clinical practice and guidelines. When new scientific evidence and/or analyses emerge, clinical practice guidelines must be updated and measures of healthcare quality adjusted accordingly.
That happened in 2009 when the United States Preventive Services Task Force (USPSTF) updated its mammography guidelines. Their comprehensive scientific evaluation concluded that the balance of benefits and harms varies based on individual risk factors for women in their 40’s. USPSTF therefore urged clinicians to explain the pros and cons and decide with women based on individual risk and preferences whether to screen. For ages 50 to 74, USPSTF found that screening every other year preserved the benefits while minimizing the risks compared to annual screening.
Based on the updated evidence and guidelines, the National Committee for Quality Assurance (NCQA), the nation’s healthcare quality measurement leader, consulted with many experts and adjusted its measures for mammography accordingly. However, not everyone has agreed.
Since then new analysis of an old study evaluating annual, rather than biennial, mammograms, received much attention. This Canadian National Breast Cancer Screening Study 25-year follow-up reached the same conclusion it did at 10 and 15 years – that annual mammograms do not reduce deaths versus simple breast exams. That is not really news.
What was news was the updated Canadian analysis’ first-ever estimate from a randomized mammography trial of over-diagnosis. Half of all cancers detected by mammography that were not found by regular breast exams were not destined to grow or kill and would not otherwise have come to clinical attention. This confirms other studies, including one that used molecular markers to estimate how often screening inadvertently flags ultralow risk disease.
Screening has benefits, but also harms from aggressively treating benign lesions. Over-diagnosis is not intentional, but is inherent in any screening program and will result in the detection of additional small indolent tumors. We have likely, and quite understandably, overestimated screening’s benefits and underestimated its harms. That is why virtually every mammography study has generated controversy, including efforts to explain why we have achieved so much less reduction in mortality or late stage disease than hoped.
To move beyond this, we need to recognize that over-diagnosis and treatment occurs and look to opportunities to improve screening to reduce them. One way is to adjust biopsy thresholds.
The Breast Imaging Reporting and Data System (BIRADS) now prompts a recommendation for biopsy with any score of 4, which spans the risk range of 3 to 95 percent. BIRADS 4A (low suspicion), 4B (intermediate suspicion), and 4C (moderate concern, but not classic for malignancy) categories could help better refine biopsy thresholds.
We further need to:
- Understand screening’s benefit in the context modern adjuvant therapy that was not part of care when the existing screening trials began 30-40 years ago;
- Explore how to better personalize screening to an individual’s risk and concerns;
- Move beyond unfounded, inflammatory assertions that attempts to tailor or improve screening are efforts to ration care.
The USPSTF recommendations are based on the balance of scientific evidence, not cost. However, the significant additional resources required for more aggressive screening that does not yield additional benefit is estimated to cost as much as $6.5 billion more each year. This is more than the National Cancer Institute’s total annual budget.
Current scientific evidence makes clear that annual screening leads to more false positives, over-treatment and costs, without improving mortality. The proponents of annual mammography claim that lives will be lost if we change; however, conclusions that mammography would have been effective cannot be drawn from studies on young women who died of breast cancer who also happen not to have been screened. ¬-xviii It only confirms that breast cancer can indeed be a very serious disease.xix
We have to find a better way to resolve this long-standing mammography debate. More arguing over old studies will not improve our current approach or change strongly held and often polarized beliefs based on existing evidence.
We also must stop screening as if one size fits all. Breast cancer is not just one disease. Some grow very slowly, others very fast, and not all patients will benefit from the same approach.
Instead, we should act on the unprecedented scientific advances in our understanding of inherited risk, density, and cancer biology to further refine our risk-benefit calculations. We also now have better screening techniques, therapies, and understanding of how to assign individual patients to the specific treatments that are best for them. We need to harness all this knowledge to shed more light and less heat on how best to screen, prevent, and treat in the modern era.
Only by better understanding who is at risk, and for which type of breast cancer, can we fine tune guidelines even more to minimize or avoid screening when prudent and target those most likely to benefit. Lets stop arguing about whether screening is good or bad and instead focus on innovation and learning how we can make it better.
Margaret E. O’Kane is President of the National Committee for Quality Assurance.
Laura Esserman is Director of the Carol Franc Buck Breast Care Center and a Professor of Surgery and Radiology at the University of California, San Francisco, School of Medicine.
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