UCSF

Background

Biennial screening mammography retains most of the benefits of annual breast cancer screening with reduced harms. Whether screening guidelines based on race/ethnicity and age would be more effective than age-based guidelines is unknown.

Methods

Mammography data from the Breast Cancer Surveillance Consortium were linked to pathology and tumor databases. The authors identified women aged 40 to 74 years who underwent annual, biennial, or triennial screening mammography between 1994 and 2008. Logistic regression was used to estimate adjusted odds ratios (OR) and 95% confidence intervals (95% CI) of adverse tumor characteristics among 14,396 incident breast cancer cases and 10-year cumulative risks of false-positive recall and biopsy recommendation among 1,276,312 noncases.

Results

No increased risk of adverse tumor characteristics associated with biennial versus annual screening were noted in white women, black women, Hispanic women aged 40 to 49 years, or Asian women aged 50 to 74 years. Hispanic women aged 50 to 74 years who screened biennially versus annually were found to have an increased risk of late-stage disease (OR, 1.6; 95% CI, 1.0-2.5) and large tumors (OR, 1.6; 95% CI, 1.1-2.4). Asian women aged 40 to 49 years who underwent biennial screening had an elevated risk of positive lymph nodes (OR, 3.1; 95% CI, 1.3-7.1). No elevated risks were associated with triennial versus biennial screening. Cumulative false-positive risks decreased markedly with a longer screening interval.

Conclusions

The authors found limited evidence of elevated risks of adverse tumor characteristics with biennial versus annual screening, whereas cumulative false-positive risks were lower. However, elevated risks of late-stage disease in Hispanic women and lymph node-positive disease in younger Asian women who screened less often than annually warrant consideration and replication.