Introduction: Women with benign breast disease (BBD) are at an increased risk of subsequent development of breast cancer. We followed a cohort of high-risk women to investigate the development of invasive breast cancer and examined differences in incidence and Gail risk among women with and without BBD.

Methods: The Women At Risk (WAR) registry is a prospectively followed cohort of women at Columbia University medical Center from 1991 to 2011. Ascertainment of progression from BBD to breast cancer was done through examination of medical records and New York Presbyterian tumor registry. Incidence rates are reported per 10,000 person-years at risk. Women with a history of BBD at baseline were diagnosed with BBD prior to enrollment in the WAR registry, women with BBD diagnosed after enrollment were classified as incident BBD. We calculated 5-year and lifetime Gail risk based on women's characteristics at baseline to compare Gail risk in women with and without BBD. For this analysis, women with incident BBD were excluded. We assessed risk of invasive breast cancer using Poisson regression analysis, with the log-transformed person-years as the offset.

Results: There were 396 women with a history of BBD at baseline. Mean 5-year Gail risk was significantly higher for women with a history of BBD as compared to women without a history of BBD at baseline (BBD (Mean±Std): 3.60±2.29 vs. No BBD: 1.94±1.68, p<0.001). We identified 26 subsequent invasive breast cancers among 396 women with BBD at baseline and 47 breast cancers among 1,322 women without BBD, with a mean follow-up of 8.6 years. Among women with BBD at baseline breast cancer incidence is 100.8 per 10,000 women years, compared to 38.6 per 10,000 woman years among women without BBD. A diagnosis of BBD at baseline resulted in an excess incidence of 62.2 per 10,000 woman years. Age-adjusted risk of invasive breast cancer was 2.45 higher in women with BBD at baseline as compared to women without BBD (RR: 2.45, 95% CI: 1.52-3.96). The average time between BBD diagnosis and invasive breast cancer diagnosis was 9.0 years. Time to breast cancer diagnosis was similar regardless of histologic type (p=0.22). After follow-up, 844 women were diagnosed with incident BBD. We identified 48 invasive breast cancers among 844 women with incident BBD, with a breast cancer incidence of 65.6 per 10,000 woman years. Incident BBD results in an excess incidence of breast cancer of 35.2 per 10,000 woman years. Age-adjusted risk of invasive breast cancer was 1.76 higher in women with incident BBD as compared to women without BBD (RR: 1.76, 95% CI: 1.18-2.64).

Conclusions: Breast cancer incidence is higher among women with BBD, contributing to the evidence of increased breast cancer risk after BBD diagnosis.

Citation Format: Laura L. Reimers, Katherine D. Crew, Mary Beth Terry. Breast cancer incidence and Gail risk in a prospective study of women with benign breast disease. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 264. doi:10.1158/1538-7445.AM2014-264