In 2016, the US Preventive Services Task Force (USPSTF) issued their final recommendation for mammographic screening for breast cancer, advising women to undergo biennial screening between the ages of 50 and 74 years (B recommendation), and that the decision to undergo screening for women aged 40-49 years should be an individual one, and a woman may wish to undergo biennial screening (C recommendation). The group based these recommendations on a 2016 evidence review that included 8 randomized trials rated to be of fair quality from their prior analysis, and supplemented these with new results from 1 trial.1 The new review also assessed, for the first time, all-cause mortality, and how disease-specific mortality benefits may vary by risk factors and frequency of screening.
The USPSTF estimated, based on a pooled analysis of breast cancer deaths during the accrual and follow-up period of 9 randomized trials, that mammography screening for women between the ages of 39 and 49 years is associated with a relative risk (RR) reduction in breast cancer mortality of 0.88 (95% confidence interval [CI], 0.73-1.003), although confidence intervals of all trials and this pooled estimate crossed 1. Based on 7 randomized trials, reviewers found a 14% disease-specific mortality reduction for women ages 50-59 years (RR 0.86; 95% CI, 0.68-0.97).1 Based on 5 randomized trials, researchers find a 33% disease-specific mortality reduction for women ages 60-69 years (RR 0.67; 95% CI, 0.54-0.83). For women ages 70-74 years, 3 trials found a pooled RR of 0.80 (95% CI, .51-1.28).1 Absolute reduction in breast cancer mortality ranged from 4.1 to 21.3 per 10,000 women screened for 10 years, depending on age of subjects.
Despite this fair and impartial summary of the evidence, the issue of mammographic screening remains controversial and must remain a choice. In their review, the USPSTF found considerable harms of screening, including false positives and overdiagnosis—detecting and treating a cancer that would otherwise not cause harm. Estimates of overdiagnosis ranged from 11 to 22 in randomized trials.1 Moreover, irrespective of age, mammographic screening failed to demonstrate statistically significant improvements in overall survival. For all age groups, pooled analysis of 9 randomized controlled trials yielded a RR of 0.99 (95% CI, 0.97 to 1.003).1
For these reasons, the USPSTF guidelines, in the 50–74-year-old cohort, should be used to identify women for whom a discussion of mammographic screening should take place, but it should not be taken to mean that mammographic screening must subsequently take place. An informed decision to decline screening is reasonable. Such an interpretation runs counter to many hospital- and insurer-based programs that provide financial incentives for higher screening rates.2
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-Vinay Prasad, MD, MPH
This article originally appeared in the July 2017 issue of The American Journal of Medicine.
