Benefits and Risks of Mammography Screening

The article by Pace and Keating in JAMA reports on their MEDLINE search of articles and meta-analyses from 1960 to 2014 that describe benefits and/or harms of mammography, individualizing screening decisions and those promoting informed decision making.

They found that mammography screening is associated with a 19% overall reduction of breast cancer mortality (approximately 15% for women in their 40s and 32% for women in their 60s). For a 40- or 50-year-old woman undergoing 10 years of annual mammograms, the cumulative risk of a false-positive result is about 61%. About 19% of the cancers diagnosed during that 10-year period would not have become clinically apparent without screening (overdiagnosis), although there is uncertainty about this estimate.

They estimated that for every 10,000 women in their 40s who undergo annual mammograms for 10 years, 5 breast-cancer deaths will be averted. Of the remainder, about 25 would die despite being treated, and 36 would be treated unnecessarily because the cancer wouldn't have become life threatening.  For every 10,000 women in their 50s and those in their 60s screened annually for 10 years, 10 and 42 breast-cancer deaths would be averted respectively. But as many as 137 women in their 50s, and 194 in their 60s would be diagnosed and treated unnecessarily.  Women in all age groups will experience angst and inconvenience because of false positives diagnoses and unnecessary biopsies.

They conclude that although mammography screening may be associated with reduced breast cancer mortality it can also cause harm.  They suggest that in order to maximize the benefit of mammography screening, decisions should be individualized based on patients' risk profiles and preferences.

Pace LE, Keating NL; A systematic assessment of benefits and risks to guide breast cancer screening decisions: JAMA. 2014 Apr 2;311(13):1327-35.

doi: 10.1001/jama.2014.1398.