1. In this observational study involving women aged 70 to 84 years with a life expectancy of at least 10 years, continuing screening past the age of 75 offered no survival benefits versus stopping screening.
2. Participants in the “stop screening” group were, on average, more likely to be diagnosed with breast cancer and to be treated more aggressively. This finding can likely be attributed to asymptomatic growth that went largely undetected in the absence of screening.
Evidence Rating Level: 2 (Good)
Study Rundown: Breast cancer screening is generally cost effective, but the burden of routine testing may begin to outweigh the benefits at older ages where competing causes of death have a proportionally greater impact on mortality. A recent meta-analysis has indicated that screening for 10 years beginning between the ages of 50 and 69 confers a statistically significant survival benefit, but limited data exists for the age groups higher than this. This study emulated a hypothetical target trial using observational data from patients between the ages of 70 and 85 who were enrolled in fee-for-service Medicare between 1990 and 2008. Among women aged 70 to 74 years, those who had annual screenings had a slightly lower risk of breast cancer death at 8 years, but this effect was absent in participants aged 75 to 84 years after adjusting for a number of confounders including baseline characteristics, time-varying screening history, and time-varying comorbidities. Across subgroups, women who stopped screening were diagnosed later and treated more aggressively due to greater undetected cancer progression. Limitations of this study included the possibility of residual confounding due to its observational nature and the relatively short follow-up.
Relevant Reading: Benefits and harms of mammography screening
In-Depth [prospective cohort]: In this population-based observational study involving Medicare beneficiaries aged 70 to 84 years who had a life expectancy of over 10 years, two preventative mammography strategies were compared: the continuation of annual screenings or stopping screenings. All women who had baseline data consistent with both strategies were cloned. Each was assigned to 1 strategy, censored when data became inconsistent, and followed until death, disenrollment from Medicare, or December 2008. This process was repeated for women of each age within the prespecified range, resulting in 15 total cohorts. During follow-up, the “continue screening” group had 1533 deaths while the “stop screening” group had 1304. For women aged 70 to 74 years, continuing screening appeared to provide marginal benefits, with an 8-year risk for breast cancer death of 2.7 deaths per 1000 women versus 3.7 deaths per 1000 women in the “stop screening” group (hazard ratio, 0.78; 95% confidence interval [CI], 0.63 to 0.95). However, only a 0.07 risk difference (95% CI, 0.93 to 1.3) was found between groups in the cohort containing women between the ages of 75 and 84 years (hazard ratio, 1.00; 95% CI, 0.83 to 1.19). The overall positive predictive value of screening was 38.5% with continuing screening and 45.3% when screening was stopped.
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