Anyone in touch with the news knows there has been heated discussion about the recent US Preventive Services Task Force breast cancer screening recommendations. The heat has been largely focused on the suggestion that routine mammograms be deferred until age 50. Less remarked on is the further recommendation that mammograms be done every other year rather than yearly.
How the the task force arrive at this?
They relied on a study that used six independently developed models to calculate the "efficiency" of 20 different mammogram screening strategies. The differing strategies started and stopped mammograms at various ages, and did mammograms either annually or every other year.
A screening strategy was considered "efficient" if it led to an improved health outcome (compared to no screening) and consumed fewer resources (compared to other screening strategies).
An "improved health outcome" was life-years gained or fewer deaths from breast cancer. Starting screening at younger ages led to more life-years gained, while continuing screening through older ages led to fewer deaths from breast cancer.
When the researchers ranked the different strategies, all 6 models predicted the most efficient approach was screening every other year. The health outcomes were close to those achieved with annual mammograms and there almost 50% were fewer false positives.
In support of using models for this analysis, the researchers said:
Our results are also consistent with current knowledge of disease biology. Slow-growing tumors are much more common than fast-growing tumors, and the ratio of slow- to fast-growing tumors increases with age, so that little survival benefit is lost between screening every year versus every other year. For the small subset of women with aggressive, fast-growing tumors, even annual screening is not likely to confer a survival advantage. Guidelines in other countries include biennial screening. However, whether it will be practical or acceptable to change the existing U.S. practice of annual screening cannot be addressed by our models.
Some have objected to the cold-hearted approach of using models to evaluate screening for breast cancer. The study using models looked at breast cancer screening from a societal, rather than individual perspective.
When physicians see individual patients, subjective values are important. While physician organizations (like the American College of Obstetrics and Gynecology) evaluate these recommendations, many women will continue to have yearly mammograms, starting at age 40.
Physicians need time in clinic to advise our patients about the timing of mammograms. And we all must be able to adjust our medical opinion and advice as new information becomes available and is analyzed.
Unfortunately, early detection helps only a subset of women with breast cancer. The greatest benefits will come when we learn more about how to prevent breast cancer.
Our society will continue to study and discuss how best to allocate breast cancer resources among prevention, early detection and treatment efforts.
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