Randomized phase II trial of denosumab in patients with bone metastases from prostate cancer, breast cancer, or other neoplasms after intravenous bisphosphonates

Purpose Patients with bone metastases and elevated urinary N-telopeptide (uNTx), representing excessive bone resorption, are at increased risk for skeletal-related events (SREs), cancer progression, and death. Osteoclast-mediated bone resorption is regulated by RANKL. We evaluated the effect of denosumab, a fully human monoclonal antibody against RANKL, in patients with bone metastases and elevated uNTx levels despite ongoing intravenous (IV) bisphosphonate (BP) therapy. Patients and Methods Eligible patients had histologically confirmed malignancy, ≥ 1 bone metastases, and uNTx levels higher than 50 nmol/L bone collagen equivalents (BCE)/mM creatinine despite IV BPs. They were stratified by tumor type and screening uNTx levels (50 to 100 or > 100 nmol/L BCE/mM creatinine), and randomly assigned to continue IV BPs every 4 weeks or receive subcutaneous denosumab 180 mg every 4 weeks or every 12 weeks. Results Among 111 patients accrued, the primary end point of uNTx levels lower than 50 nmol/L BCE/mM creatinine (uNTx < 50) at week 13 was achieved by 49 (71%) of 69 patients in the denosumab arms, compared with 10 (29%) of 35 patients in the IV BP arm (P <.001). The proportion of patients with uNTx lower than 50 was maintained at week 25 (64% denosumab arms; 37% IV BP arm; P =.01). The incidence of SREs was six (8%) of 73 and six (17%) of 35 in the denosumab group and IV BP group, respectively. Rates of adverse events were similar between treatment groups. Conclusion Among patients with elevated uNTx despite ongoing IV BP therapy, denosumab normalized uNTx levels more frequently than the continuation of IV BP. Fewer patients receiving denosumab experienced on-study SREs than those receiving IV BPs.