Molecular profiles of screen-detected breast cancers from a Turkish breast cancer screening program.

Abstract

e12545 Background: TurkishBahcesehir Breast Cancer Screening Project is a 10-year organized population based screening program carried out in one of the largest counties in Istanbul, Turkey. The aim of this study is to determine the biological features of screen detected breast cancers detected during the initial 4-year study period as an interim analysis. Methods: Between January 2009 and December 2012, a total of 5938 women with ages 40–69 years were recruited in this prospective study. Two-view mammographies were obtained by 2-year intervals, and classified according to Breast Imaging Reporting and Data System of the American College of Radiology (ACR). Patient and tumor characteristics were analysed for those diagnosed with breast cancer. Tumors were stained for estrogen (ER) and progesterone receptors (PR), HER2-neu and Ki-67 by immunohistochemistry. Results: A total of 49 breast cancers (% 0.83) were detected during the study period. The median age was 50 (40-70). The majority of patients (78%) were stage 0 or 1, whereas 23 patients (47%) were <50 age. Of 49 tumors, 38 (78%) were invasive cancers and 11 (22%) were ductal carcinoma in situ. Forty-four patients (90%) underwent breast conservation, whereas 35 patients (75%) had sentinel lymph node biopsy. Of 38 invasive cancers, 24 (63%) were ductal carcinoma and 8 (21%) were lobular cacinoma. Among 31 invasive cancers stained for ER, PR, HER2-neu and Ki67, the majority of them (92%) were hormone receptor positive, whereas 13% were HER2-neu positive and 58% had low Ki67 levels (<14). As molecular subtypes, the majority of them were found to be either luminal A (48%) or luminal B type (42%), whereas other nonluminal HER2 (7%) and triple negative cancers (3%) were less frequently detected. Conclusions: Our findings suggest that the majority of screen-detected breast cancers exhibit either luminal A or B subtype. However, more aggressive subtypes such as nonluminal HER2-neu or triple negative cancers are less likely to be detected by mammographic screening programs, requiring other preventive strategies.