Background: Atypical ductal hyperplasia and atypical lobular neoplasia are common benign breast diseases that increase breast cancer risk. We performed a cohort analysis that compared atypia patients for additional risk factors to asses the effect on breast cancer risk by atypia status. Methods: This longitudinal cohort study used data from the Women At Risk High-Risk Registry at Columbia University Medical Center, New York. Women with atypia were compared to women without atypia across known risk factors to determine the combined effect on breast cancer development. Odds ratios (ORs) stratified by atypia status were calculated for each risk factor of interest with 95% confidence intervals (95% CIs). P values were calculated to determine statistical significance. Results: The study population included 1598 high-risk women, 921 (57.6%) of whom had a history of biopsy-proven atypia. The remaining 677 high-risk women (42.4%) did not have atypia. Fifty women (3.1%) developed breast cancer. Alcohol was significantly associated with the development of breast cancer (P = 0.02) and increased breast cancer risk among women with atypia (OR, 2.13; 95% CI, 0.95-4.81) compared to women without atypia (OR, 1.71). The odds of breast cancer were higher for atypia patients with first-degree relatives (OR, 1.48; 95% CI, 0.64-3.35) compared to women with a relative and no atypia diagnosis (OR, 0.98; 95% CI, 0.41-2.63). The other risk factors of interest did not differ significantly by atypia status. Conclusions: Atypia patients who drank alcohol and had a first-degree relative with breast cancer have an increased risk of breast cancer compared to those without atypia. Continued understanding of the high-risk population will lead to more individualized protocols for risk reduction and prevention.
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