Denosumab as an add-on Neoadjuvant Treatment (GeparX)

RANK ligand (RANKL), a key factor for bone remodeling and metastasis, is crucial for the development of mouse mammary glands during pregnancy. RANKL functions as a major paracrine effector of the mitogenic action of progesterone in mouse and human mammary epithelium via its receptor RANK and has a role in ovarian hormone-dependent expansion and regenerative potential of mammary stem cells. Pharmacologic inhibition of RANKL attenuates the development of mammary carcinoma and inhibits metastatic progression in multiple mouse models. In a retrospective analysis of 601 patients treated in the GeparTrio study with chemotherapy (TAC) it could be demonstrated that elevated expression of RANK (immunohistochemical score \> 8.5 using the N-1H8 antibody by Amgen) was found in 14.5% of patients overall, with a significant predominance in patients with hormone-receptor-negative disease (33.7% vs 6.4% tumors positive for RANK). Expression of RANK was associated with a higher pathological complete response rate (pCR) (23.0% vs 12.6%) but with a shorter disease-free and overall survival. The ABCSG-18 study showed that adjuvant denosumab reduces clinical fractures, improves bone health, and can be administered without added toxicity. Moreover denosumab improves disease-free survival in postmenopausal woman with hormone receptor positive breast cancer. It appears therefore reasonable to test denosumab, a clinically available antibody against RANKL in patients with hormone-receptor-negative primary breast cancer as an adjunct to neoadjuvant chemotherapy for its ability to increase pCR rate and improve outcome in relation to the expression of RANK.