Politics Gets in the Way of Evidence-Based Medicine

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Medicine is purportedly moving into an evidence-based era where treatments are scientifically evaluated for the value they add to patient care and disease prevention. Think again. Medical care continues to be influenced by emotional and political factors that disregard and sometimes threaten scientific inquiry. 

Look no further than the just released mammography screening guidelines issued by the U.S. Preventive Services Task Force (USPSTF). After examining the available evidence, USPSTF concluded that the balance of potential benefits and harms does not justify the current standard of starting annual screening at age 40. Instead, they propose that mammogram screening for average-risk women start at age 50 and continue every other year until age 74. They suggest that women younger than 50 consult with their physicians to determine if their history and risk factors warrant starting mammography earlier. 

The USPTF is not some fly-by-night outfit. This independent panel of primary care and preventive medicine experts is so well respected that the Affordable Care Act specified that private health insurance plans cover services given a USPSTF A or B Grade (high certainty of substantial net benefit or moderate certainty of moderate to substantial net benefit) without out-of-pocket cost. Yet their announcement has been greeted with howls of disapproval by physician and patient advocacy groups and by politicians who are working to make sure that the recommendations won’t be adopted. 

USPSTF’s mammography recommendations mirror guidelines used around the world. The U.S. has been unique in initiating annual screening at age 40 and continuing indefinitely. Other countries start at 50 and screen every two to three years up to 70-74 years old. Other impartial medical groups concur with USPSTF’s recommendations. This past year, the American College of Physicians High Value Care Task Force made identical recommendations. The International Agency for Research on Cancer recommended starting screening at 50 and continuing to 69. Even the American Cancer Society--long the strongest proponent of annual screening beginning at 40--recently compromised and recommended starting annual screening at 45, switching to biennial screening for women between 55 and 70, and limiting mammograms for women over 70 to those who remain in good health. 

The USPSTF acknowledged that screening women in their 40s can reduce breast cancer deaths, but the benefits are less than in older women and the harms are higher, so there is only a moderate certainty of small net benefit (Grade C). And the harms are substantial:

-- Overdiagnosis — the diagnosis and treatment of early cancers that would have never become apparent and would not have threatened a woman’s health — occurs in approximately 20 percent of cancer diagnoses over ten years of screening. It is more common when screening starts before fifty and is annual.

-- False positive results leading to unnecessary testing and sometimes surgery occur in 61 percent of women screened annually for ten years. This rate declines to 42 percent if screening is done biennially. Starting screening at 40 increases the number of studies and the likelihood of a false positive result.

-- False negative results (missing a cancer) may delay cancer diagnosis when patients and physicians are falsely reassured by a negative mammogram and ignore other manifestations of the disease. False negatives are more common in younger women.

Despite these facts, the USPSTF guidelines have been censured by numerous patient advocacy and medical groups who emphasize the benefits of screening but rarely mention the harms. Criticisms often amount to little more than anecdotes and personal opinions devoid of context or scientific citation. Senators and representatives of both parties, responding to an earlier draft of USPSTF guidelines, introduced the Protecting Access to Lifesaving Screenings Act (PALS Act) placing a two-year moratorium on implementing the USPSTF recommendations. The PALS Act became law as part of the December 2015 Omnibus Spending Bill. 

The PALS Act ensures that women will continue to be subjected to screening that starts too early and is done too frequently. The Act is also disturbing in another regard: A section of the Senate version of the bill (S.1926) directed the Government Accountability Office to study “the methodologies and processes by which the [USPSTF] develops recommendations regarding preventative services, including the transparency of such methodologies and processes … and the propriety of the data and other information on which the Task Force relies….” The section, thankfully dropped from the final bill, sets the stage for future government intervention into scientific research when advocacy groups and politicians disagree with the outcomes. USPSTF’s volunteer members have already taken substantial heat without being subjected to a government witch hunt. 

Popular beliefs and prejudices should not determine health care standards or interfere with unbiased scientific inquiry. The accumulated evidence about mammography screening is clear. As an editorial that accompanied the USPSTF announcement in the Annals of Internal Medicine noted, “Strong recommendations for screening average-risk women in their 40s, for annual rather than biennial screening in any age group, or for continuing screening in elderly women would misrepresent the net benefit of mammography in these groups. Guidelines that mislead women about the net health benefits they can expect from mammography would disrespect our mothers, wives, daughters, and sisters.”

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