Screening for breast cancer with mammography

Area of Science:

• Oncology
• Public Health
• Radiology

Background:

• Mammographic screening for breast cancer has varying estimates of benefits and harms.
• National policies on mammography screening differ globally.

Purpose of the Study:

• To assess the impact of mammographic screening on breast cancer mortality and morbidity.
• Evaluate the net effect of screening interventions.

Main Methods:

• Systematic review of randomized controlled trials comparing mammography screening with no screening.
• Data extraction from eligible trials, including contacting study authors for additional information.
• Analysis of mortality and morbidity outcomes, considering trial quality and randomization adequacy.

Main Results:

• Seven eligible trials included 600,000 women; three adequately randomized trials showed no significant reduction in breast cancer mortality.
• Suboptimal randomization trials suggested a significant reduction in breast cancer mortality.
• Screening increased lumpectomies and mastectomies (RR 1.31) and radiotherapy use.
• Overdiagnosis was estimated at 30%, leading to overtreatment of healthy women.

Conclusions:

• Mammographic screening may offer a modest 15% reduction in breast cancer mortality, but this is uncertain.
• Screening results in significant overdiagnosis and overtreatment, with 10 healthy women treated for every 2000 screened over 10 years.
• The balance of benefits and harms from mammographic screening is unclear, with potential for psychological distress from false positives.