Abstract A15: Breast cancer subtype subsequent to a benign breast biopsy among African American women

Introduction: Most clinical models to estimate risk of invasive breast cancer include history of benign breast disease (BBD) as a covariate, as these women represent a higher risk group compared to the general population. A better understanding of the association between BBD and breast cancer is necessary to improve the utility of these risk models, particularly with respect to tumor subtype. This may be especially important for African American women who are more likely to present with aggressive cancers compared to white women. Here we present tumor subtypes from a higher risk cohort of African American women with a history of BBD. Methods: Benign breast biopsies from 3,865 African American women with BBD diagnosed from 1997-2010 were examined for 14 benign features, and followed for subsequent breast cancers in metropolitan Detroit, Michigan using medical records and data from the Detroit Surveillance, Epidemiology and End Results (SEER) program. Immunohistochemistry analysis was performed for the following 6 markers: estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), Ki-67, epidermal growth factor receptor (EGFR) and cytokeratin 5/6 (CK 5/6) in order to categorize the subsequent breast cancers by subtype. Briefly, ER and PR were utilized to classify tumors as luminal or non-luminal, and then further classification was made based HER2. Luminal tumors were also classified by Ki-67 expression, and triple negative tumors (ER/PR/HER2 negative) were further classified based on expression of either CK5/6 or EGFR, resulting in 6 categories. Results: 210 women (5.4% of the total cohort) with a subsequent breast cancer were identified over a median follow-up time of 12.3 years (range: 0.6 - 18.0). Analysis of all 6 markers is complete for half of the tumors (104). The majority of the subsequent cancers were invasive (n=72, 69.2%). Most of the invasive tumors were luminal B, HER2- (37.5%), followed by luminal A (31.9%), triple negative (19.4%), non-luminal, HER2+ (6.9%) and luminal B, HER2+ (4.2%). Of the 14 triple negative cancers (19.4%), 8 were negative for CK5/6 and EGFR (5 negative phenotype, 57.1%) and 6 were core basal (42.9%). Among the 32 in situ tumors, the majority were luminal A (n=26, 81.3%), followed by luminal B, HER2- (n=5, 15.6%) and there was a single tumor classified as 5 negative. Compared to population-based SEER data from 5,268 African American women with invasive breast cancer and available data on 3 markers (ER, PR, and HER2) diagnosed in 2010, our cohort is similar with respect to tumor subtype. Conclusions: The women with a previous benign breast biopsy in our cohort who develop a subsequent breast cancer have subtypes that are similar to the general African American population in the United States. Thus, our BBD cohort represents the full spectrum of invasive breast cancers with respect to subtype, including triple negative tumors. Citation Format: Julie J. Ruterbusch, Michele L. Cote, Julie Boerner, Eman Abdulfatah, Baraa Alosh, Vishakha Pardeshi, MHD Fayez Daaboul, Woodlyne Roquiz, Rouba Ali-Fehmi, Sudeshna Bandyopadhyay. Breast cancer subtype subsequent to a benign breast biopsy among African American women. [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 A15.