Abstract CT101: D-BEYOND: A window of opportunity trial evaluating denosumab, a RANK-ligand (RANKL) inhibitor and its biological effects in young pre-menopausal women diagnosed with early breast cancer

Background Breast cancer (BC) in young women has unique biology and poor prognosis. Previous reports suggest that they often express RANKL , which was also shown to play a role in mammary tumorigenesis and the etiology of BRCA1/2 related BC. Here, we present the primary results of D-BEYOND, a window of opportunity study investigating the biological activity of the RANKL inhibitor; denosumab in pre-menopausal BC patients. Methods D-BEYOND is a prospective, phase IIa, single-arm, multicenter study assessing the effect of denosumab on BC biology in premenopausal women with early BC (NCT01864798). Patients received two subcutaneous injections of denosumab (120mg), one week apart, followed by breast surgery. Blood, tumor and normal adjacent breast tissue were collected at baseline and at surgery. The primary endpoint was geometric mean change in tumor Ki67 assessed by immunohistochemistry (IHC) from baseline to surgery. Absolute Ki67 responders were defined as having Results A total of 27 patients were enrolled in the study between October 2013 and July 2016. The median age was 45 years (range 35-51 years). Tumors of 21 patients were hormone receptor positive (77.8%), 4 were HER2 positive (14.8%) and 2 were triple negative (7.4%). No serious adverse events were reported, the most frequent non-serious adverse event being arthralgia (14.8%). After treatment, serum levels of CTX and sRANKL decreased in all patients ( P P = 0.009, 95% CI 0.56-0.91). There was no significant reduction of Ki67 values from baseline (geometric mean change after treatment; 0.98, 95% CI 0.76-1.26; P = 0.90) and there were no absolute Ki67 responders. Twenty-four pre- and post-treatment tumor pairs were available for RANK/L staining and TILs assessment. There was no significant difference in RANKL and RANK H-score in tumors after treatment ( P = 0.842, P = 0.142, respectively) but we observed a decrease of RANKL H-score in 3 tumors (12.5%) and an increase of RANK H-score in 5 tumors (20%). Interestingly, there was a significant increase in the percentage of stromal TILs after treatment (geometric mean change of 2.51, 95% CI 1.58-3.97; P = 0.004). There were 10/24 patients (41.7%) with a change in TILs of at least 10%, all of them having an increase in TILs presence ( P = 0.002). Conclusion Short course of denosumab did not reduce tumor proliferation rate. However, it induced a significant increase in TILs. These findings suggest that denosumab may potentiate immunotherapy efficacy, at least in young BC patients. Additional results including immune cell profiling by multiplex IHC and RNA-sequencing of tumor and normal tissues will be presented at the meeting. Citation Format: Bastien Nguyen, Marion Maetens, Roberto Salgado, David Venet, Peter Vuylsteke, Laura Polastro, Hans Wieldiers, Philippe Simon, Geoff Lindeman, Denis Larsimont, Gert Van den Eynden, Chloe Velghe, Francoise Rothe, Soizic Garaud, Stefan Michiels, Karen Willard-gallo, Hatem A. Azim, Sherene Loi, Martine Piccart, Christos Sotiriou. D-BEYOND: A window of opportunity trial evaluating denosumab, a RANK-ligand (RANKL) inhibitor and its biological effects in young pre-menopausal women diagnosed with early breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr CT101.