Annals of Internal MedicineEstimating Breast Cancer Overdiagnosis After Screening Mammography Among Older Women in the United States

The issue of overdiagnosis in breast cancer screening is a growing concern, particularly for older women. A retrospective cohort study was conducted to estimate the extent of overdiagnosis by comparing the cumulative incidence of breast cancer among older women who continued screening with those who did not. Utilizing data from Medicare claims linked to the SEER program, the study sheds light on the potential harms of screening for women aged 70 and above.

Study Design:

• Background: Overdiagnosis as a harm of breast cancer screening, particularly for older women.
• Objective: Estimation of overdiagnosis among older women by age.
• Design: Retrospective cohort study using competing risk models, stratified by age.
• Setting: Fee-for-service Medicare claims, linked to the SEER program.
• Patients: 54,635 women included in the study, 70 years and older who had been recently screened.
• Measurements: Breast cancer diagnoses and death for up to 15 years of follow-up.

Key Findings:

• Ages 70-74: 6.1 cases per 100 screened vs. 4.2 per 100 unscreened, 31% potentially overdiagnosed.
• Ages 75-84: 4.9 cases per 100 screened vs. 2.6 per 100 unscreened, 47% potentially overdiagnosed.
• Ages 85 and older: 2.8 cases per 100 screened vs. 1.3 per 100 unscreened, up to 54% overdiagnosis.
• No statistically significant reductions in breast cancer-specific death associated with screening.

Conclusion:

• Continued breast cancer screening was associated with greater incidence of breast cancer, suggesting overdiagnosis may be common among older women. The balance between harms of overdiagnosis and benefits remains an important question.

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Did You Know?
Overdiagnosis in breast cancer screening can lead to unnecessary treatments and emotional stress; studies have estimated that up to 22% of all detected breast cancers might be overdiagnosed.