Abstract P3-05-11: Breast cancer characteristics in premenopausal women by contraception method

Abstract INTRODUCTION: Our knowledge regarding the levonorgestrel intra-uterine device (LNG-IUD) and breast cancer (BC) risk is limited. As the LNG-IUD is a widely used contraception method, we here explored receptor expression in BC, in women < 56 years, by having a LNG-IUD at diagnosis. We aim to validate the findings of a previous cohort treated in the University Hospitals Leuven, where we observed proportionally more progesterone receptor (PR), lower human epidermal growth factor receptor 2 (HER2) expression and more ER+PR+HER2- subtypes in LNG-IUD users compared to non-LNG-IUD users. MATERIALS AND METHODS: We conducted a retrospective observational monocentric study from 2015 until 2020. We included patients < 56 years consulting the University Hospitals Leuven for primary invasive BC, who were treated with primary breast surgery or neoadjuvant therapy. We compared patient and tumor characteristics, especially receptor subtypes in LNG-IUD users at diagnosis with non- LNG-IUD users. Group comparisons with regards to receptor subtypes were performed by the Chi-square test, all tests were evaluated at a two-sided 5% significance level. RESULTS: Of the 1347 patients with BC included in this study, 272 had a LNG-IUD at diagnosis. The LNG-IUD users were more likely ER (85.29% vs 77.77%, p=0.006) and PR positive (80.88% vs 70.95%, p< 0.001) compared to the control group. Additionally, we observed more ER+PR+HER2- (68.75% vs 58.62%, p=0.002) and fewer ER-PR- HER2- (10.29% vs 15.66%, p=0.025) subtypes when comparing with the control group. CONCLUSION: This internal validation study confirmed invasive BC, diagnosed in women under age 56, to be more likely PR+ and ER+PR+HER2- if they used a LNG- IUD at BC diagnosis when compared to non-LNG-IUD users. Citation Format: Inés De Maeyer, Eline Borowski, Karen Van Baelen, Annouschka Laenen, Ines Nevelsteen, Hans Wildiers, Sileny Han, Ann Smeets, Thaïs Baert, Kevin Punie, Patrick Neven. Breast cancer characteristics in premenopausal women by contraception method [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-05-11.