What is the efficacy of breast cancer screening in the early detection of breast cancer?

Updated: Feb 04, 2021
  • Author: Pavani Chalasani, MD, MPH; Chief Editor: John V Kiluk, MD, FACS  more...
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Whereas early detection has been advocated as a primary defense against the development of life-threatening breast cancer, questions have been raised in the past few years regarding the age at which to initiate, the modality to use, the interval between screenings, whether to screen older women, and even the impact on breast cancer−related deaths. It is widely believed that breast tumors that are smaller or nonpalpable and that present with a favorable tumor marker profile are more treatable when detected early.

A survival benefit of early detection with mammography screening has been demonstrated. [84, 85] A review that used seven statistical models determined that the use of screening mammography reduced the rate of death from breast cancer by 28–65% (median, 46%). [84] A meta-analysis found that screening mammography reduces breast cancer mortality by about 20–35% in women 50–69 years old and slightly less in women 40–49 years old at 14 years of follow-up. [85]

In the UK Age trial, breast cancer mortality in the first 10 years after diagnosis was significantly lower (rate ratio [RR] 0.75) in women who received annual screening mammography from age 40-49 years than in those invited for screening at age 50 years and every 3 years thereafter. During the remainder of the 17-year follow-up period, however, reduction in breast cancer mortality was not evident (RR 1.02). [86]

In contrast, 25-year follow-up of 89,835 women in the Canadian National Breast Screening Study found that annual mammography in women aged 40-59 did not reduce mortality from breast cancer beyond that of physical examination or usual care when adjuvant therapy for breast cancer is freely available. Findings for women aged 40-49 and 50-59 were almost identical. Moreover, 22% (106/484) of invasive breast cancers detected by screening mammography were over-diagnosed, representing one over-diagnosed breast cancer for every 424 women who received mammography screening in the trial. [87]  

A large-scale, population-based, observational study by García-Albéniz et al concluded that continuing annual breast cancer screening past age 75 years did not result in substantial reductions in 8-year breast cancer mortality compared with stopping screening. The study used data from 1,058,013 women enrolled in Medicare across the United States during 2000-2008. [88]

In women aged 70 to 74 years, continued screening resulted in a slightly reduced 8-year rate of breast cancer death: 2.7 deaths per 1,000 women, compared with 3.7 for those who stopped screening. In those aged 75 to 84 years, comparable figures were 3.8 versus 3.7 deaths per 1,000 women (hazard ratio, 1.00 [CI, 0.83 to 1.19]). [88] Although breast cancer was diagnosed more often in women who continued screening, that did not translate to a significant reduction in deaths because breast cancer is less successful treatment in older women. [89]

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