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, > or = 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.