Breast Cancer Screening Starting at Age 40 in the United States

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  1. Katy JL Bellteacher12,
  2. Brooke Nickelprincipal investigator1 2,
  3. Thanya PathiranaLecturer2 3,
  4. Mitzi Blennerhassettpatient activist4,
  5. Stacy Carterteacher2 5
  1. 1Sydney School of Public Health, University of Sydney, New South Wales, Australia
  2. 2Wiser Healthcare Research Collaboration, Australia
  3. 3School of Medicine and Dentistry, Griffith University, Sunshine Coast, Queensland, Australia
  4. 4Patient Representative, York, UK
  5. 5Australian Centre for Health Engagement, Evidence and Values, School of Health and Society, University of Wollongong, New South Wales, Australia
  1. Correspondence to: KJL Bell katy.bell{at}sydney.edu.au

New recommendation could cause more harm than good

The U.S. Preventive Services Task Force has updated its recommendation for the age at which all women should begin mammography screening, lowering it from age 50 to age 40.1 This change immediately affects more than 20 million American women and others assigned female at birth ages 40 to 49,2 with implications far beyond the United States.

Such a major change would have to reflect new data from randomized trials or trends in cancer mortality. But none of these data were found in the commissioned evidence report,3 and breast cancer mortality has been declining, particularly among women under 50.4 The new recommendation appears to be based on two interrelated considerations. The first is recognition of the inequality in breast cancer mortality between black and white women in the United States, and a commitment to reducing that inequality. The second is statistical modeling of a hypothetical population that found that starting screening at age 40 would reduce breast cancer mortality, particularly among black women.5

Making health policies and systems anti-racist and more equitable is urgent and imperative. But there is little empirical evidence that lowering the screening age will do this. We share the concerns of others46 about the task force’s increasing reliance on modeling rather than empirical evidence. Modeling has reported a more favorable benefit-to-risk ratio for all population groups than clinical trial evidence and has made several assumptions that may not represent reality,78 including low numbers of non-progressive or rapidly growing cancers (for which screening provides no benefit), high uptake, and large mortality benefits, particularly for Black women.

Racial inequality in breast cancer mortality in the United States has been observed since the widespread adoption of screening mammography (and adjuvant endocrine therapy) in the 1980s.9 Screening primarily benefits women with hormone receptor (HR)-positive cancers; Hormone receptor (HR)-negative tumors are more aggressive and tend to be diagnosed at later stages, in younger women, and are missed by mammography screening.6 Hormone receptor (HR)-negative tumors are more common in Black women due to hereditary reasons and social determinants of health.9 Rather than expanding mammography screening to younger women, efforts are needed to address the systemic inequities that underlie racial inequities in breast cancer care, particularly in access to high-quality, timely, and effective care and treatment.49

Uncertain evidence

Globally, the United States may be an outlier in making a strong recommendation to begin population-based mammography screening at age 40 rather than age 50.101112 The working group’s evidence report found uncertain evidence of a potential mortality benefit in women aged 40 to 49 years: the 95% confidence interval ranged from six additional deaths to 89 fewer deaths per 100,000 people screened.3 None of the included trials reported a significant reduction in breast cancer mortality with screening, including the UK Age trial, the largest (n = 160,921) and most recent trial specifically designed to determine the effectiveness of screening in women in their 40s.13 This small and uncertain benefit must be weighed against the harms.

Rates of false-positive mammograms were highest among women aged 40 to 49 years: 12,120 (95% CI 10,560 to 13,870) per 100,000 examined. Recommendations for additional diagnostic imaging were also highest among women aged 40 to 49 years: 12,490 (10,930 to 14,230) per 100,000. Many women will also require medical care and procedures such as surgical biopsies, resulting in significant costs to the health care system as well as potential out-of-pocket costs.14 Adverse psychosocial consequences, such as anxiety and lack of time in busy lives for follow-up, represent additional burdens.

Clinical trial estimates of overdiagnosis (cancers that would never have caused symptoms or death if they had not been detected and treated) range from 11% to 22% of cancers detected. Most overdiagnosed cases will also be overtreated with surgery (with or without adjuvant radiation therapy) and hormone therapy.1516 They will not benefit from this, but they may suffer consequences – because of the adverse effects of surgery and hormone therapy, and because of an increased risk of coronary heart disease and other cancers after radiation therapy.15 Finally, although there are no clinical data on the effects of mammography, one modelling report found that there could be seven additional deaths from radiation-induced breast cancer per 100,000 women with biennial screening starting at age 40 (12 deaths) rather than at age 50 (5 deaths).17

Better Pathways to Equity

Lowering the age of mammography screening offers only marginal health benefit to individuals, with a significantly increased risk of harm. Screening is also resource intensive for health systems, drawing on funds,14 clinician hours18 and facilities, all of which contribute to the carbon footprint of health care.19 This diverts resources that could be better used elsewhere, for example to improve access to effective cancer treatments and care in underserved communities.20 The opportunity costs are even more pressing in low- and middle-income countries.2021

Health systems around the world must be transformed to eliminate systematic racism and discrimination and address health inequities. Rather than adopting the new US recommendations, policymakers should work with communities to co-design initiatives to address the root causes of racial inequity in breast cancer care for Black women and other underserved groups. Patients16 and the public22 must be empowered and actively supported to understand, participate in, and influence practical and policy decisions, including the design of screening programs.

Footnotes

  • Conflicts of interest: We have read and understood the BMJ policy on declaration of interests and declare the following: MB campaigned against the Age X trial and breast cancer screening, although no funding was involved.

  • Provenance and peer review: Commissioned; external peer reviewed.



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