Abstract PS03-09: Age-related normal breast tissue features differ in women with germline BRCA1/2 mutations

Abstract Ageing, a breast cancer risk factor, can be reflected in histologically normal breast tissue (NBT). However, the relationship between age-related histological features and cancer risk is not fully understood. We propose that biological and microscopic features can be identified in seemingly histologically NBT in gBRCA1/2m carriers that are indicative of the earliest tissue changes of breast cancer, potentially as a result of accelerated tissue ageing. To study NBT, we have put in place a unique and scalable repository, named OASIS, storing currently >2,000 digitised whole slide images (WSI) of H&E-stained NBT from individuals with long clinical follow-up. These tissues are from individuals with a spectrum of risk for developing breast cancer and derived from reduction surgery from non-gBRCA1/2m carriers, risk reducing masectomies, and from contralateral and peri-tumoural NBT from gBRCA1/2m carriers and women with breast cancer. Across 6 NBT resources, 70 selected WSIs were manually annotated for epithelial cells, fibrous stroma and adipocytes, resembling the "ground truth". Extensive comparisons of different tile sizes, tile overlapping ratios, stain normalisation techniques and deep learning (DL) feature extractors were conducted to implement a Tissue-Classifier, which achieved 95% accuracy in 3-fold cross-validation. Based on the MobileNet architecture, a DL-framework achieved a sensitivity of 81.2% and specificity of 81.8% (84.7% AUC) in predicting Tissue-Age based on discernible histological patterns in healthy women. In gBRCA1/2m carriers, we discovered features of accelerated tissue ageing (e.g. degree of lobule involution), indicating that the biological NBT age differs from their chronological age. Our DL-based framework robustly captured histological patterns to predict tissue components and age. The global organisation of these patterns showed variations in WSIs of women with different risks of developing breast cancers, which may provide new insights into premalignant alterations in NBT. Citation Format: Anita Grigoriadis, Mario Parreno-Centeno, Siyuan Chen, Gregory Verghese, Esther Lips, Cheryl Gillett, Louise Jones, Sarah Pinder. Age-related normal breast tissue features differ in women with germline BRCA1/2 mutations [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS03-09.