Introduction: The majority of the 1.6 million breast biopsies performed annually in the United States are benign; however, several breast cancer risk models consider a benign biopsy a factor that increases risk of subsequent breast cancer. Fibroadenomas (FA), benign tumors of epithelial and stromal tissue, occur frequently in premenopausal women and more frequently in African American (AA) women than European American (EA) women. A small increased risk of subsequent breast cancer due to FA has been reported in some studies of EA women. We sought to investigate whether the risk of this lesion differs for AA women.

Methods: Benign breast biopsies from 3895 AA women diagnosed between 1997 and 2010 in metropolitan Detroit were reviewed for 12 benign features including FA, ductal ectasia, fibrosis, apocrine metaplasia, ductal hyperplasia, lobular hyperplasia, calcifications, cysts, intraductal papilloma, radial scar, sclerosing adenosis, and columnar alterations. These features were also used to categorize FA into simple and complex FA, where complex FA occurs when FA is accompanied by at least one of the following features: cysts, calcifications, apocrine metaplasia or intraductal papilloma. Women were followed for subsequent breast cancer using the Detroit Surveillance, Epidemiology, and End Results (SEER) cancer registry. Associations between FA and other benign lesions were examined using chi-square tests. Risk of breast cancer was estimated by relative risk ratios and 95% confidence intervals calculated using logistic regression. All models were adjusted for age at biopsy and additionally adjusted for presence of proliferative disease with or without atypia.

Results: Of the 3895 AA women, 46.5% presented with FA on biopsy. FA occurred more frequently in biopsies of younger women (p-value < 0.001) and were less likely to include the other benign lesions assessed (all p-value < 0.001). Of the 210 identified breast cancers that developed in this cohort, 72 cancers developed in women with FA on biopsy. FA were associated with a reduction in risk of breast cancer after adjusting for age at biopsy (RR=0.64, 95% CI: 0.48, 0.86) compared to women without FA on biopsy. Reduction in risk was somewhat attenuated when analysis was adjusted for proliferative disease with or without atypia (RR = 0.67, 95%CI: 0.48, 0.936). Similar associations were seen with simple FA (RR =0.61, 95% CI: 0.35, 1.01) and complex FA (RR =0.70, 95% 0.35, 1.01) after adjustment for age at biopsy and proliferative disease with or without atypia.

Conclusions: FA are negatively associated with other benign breast disease features. Risk of breast cancer may be reduced in women with FA compared to women with other types of benign lesions. These findings have important implications for modeling breast cancer risk particularly among AA women for whom FAs are common.

Citation Format: Asra N. Shaik, Julie J. Ruterbusch, Eman Abdulfatah, Marcel T. Ghanim, MHD Fayez Daaboul, Visakha Pardeshi, Rouba Ali-Fehmi, Daniel W. Visscher, Sudeshna Bandyopadhyay, Michele L. Cote. Fibroadenomas on benign breast biopsy and subsequent breast cancer risk in an African American cohort. [abstract]. In: Proceedings of the AACR Special Conference: Improving Cancer Risk Prediction for Prevention and Early Detection; Nov 16-19, 2016; Orlando, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2017;26(5 Suppl):Abstract nr A16.

©2017 American Association for Cancer Research.
2017
American Association for Cancer Research.