Secondary prevention: screening for breast cancer

Area of Science:

• Oncology
• Preventive Medicine
• Radiology

Background:

• Early detection of breast cancer through screening may improve cure rates for some patients.
• The natural history of breast cancer varies significantly, impacting the behavior of screen-detected tumors.
• Proving screening efficacy requires comparing mortality rates between screened and unscreened populations, not just survival of detected cancers.

Purpose of the Study:

• To evaluate the effectiveness of breast cancer screening in reducing mortality.
• To compare different breast cancer screening methods.
• To investigate the optimal frequency and cost-effectiveness of breast cancer screening.

Main Methods:

• One randomized controlled trial (RCT) comparing breast cancer mortality in screened versus unscreened women.
• Evaluation of mammography, clinical breast examination, and breast self-examination as screening tools.
• Ongoing trials in Canada and Europe to confirm findings and explore other issues.

Main Results:

• A published RCT demonstrated a one-third reduction in breast cancer deaths in the screened group compared to the control group.
• This mortality reduction persisted for up to 14 years post-screening invitation.
• Mammography is the most sensitive and specific screening method with minimal radiation risk, though it may lead to overdiagnosis.

Conclusions:

• Breast cancer screening, particularly mammography, can significantly reduce breast cancer mortality.
• Further research is needed to determine optimal screening frequency and cost-effectiveness.
• Clinical breast examination may be useful for premenopausal women, while breast self-examination's effectiveness and compliance are uncertain.