Osteoporosis is a global health problem with fragility fractures being the dreaded consequences as they bring about serious morbidities and significant mortality (1). Bone mineral density (BMD) T-score ≤-2.5 is one of the operational definitions of osteoporosis, as BMD T-score correlates with the fracture risks (2). The pathophysiology for the most common type of osteoporosis – postmenopausal osteoporosis – is the increase in bone resorption secondary to oestrogen deficiency after menopause (3). For most people diagnosed to have osteoporosis, anti-resorptive is the treatment of choice (4). In this class of agents, subcutaneous denosumab injection every 6 months is an option especially for those who do not tolerate bisphosphonates or have contraindications to bisphosphonates (2). In FREEDOM trial and its extension, denosumab has been shown to increase BMD for up to 10 years continuously as long as it is administered as scheduled (5).

As denosumab received FDA approval back in 2010 (5), many patients with osteoporosis may have now reached the stage of denosumab treatment for 10 years. Discontinuation of denosumab without transitioning to alternative therapy is well recognised to be associated with rebound-associated bone loss and even multiple vertebral fractures (6). Hence, guidance has been offered from professional bodies such as the European Calcified Tissue Society (ECTS) regarding the proper management of denosumab discontinuation based on limited evidence (7). In patients with high fracture risk who have not yet reached the treatment target, some of them might require continuation of denosumab treatment beyond 10 years based on individualised decision (7). Data supporting the efficacy beyond 10 years is lacking, except for a study using mathematical modelling to predict the BMD trajectory (8).

Hence, we conducted this retrospective single-centre cohort study of patients with osteoporosis who had been treated for at least 20 doses of denosumab to study the factors associated with subsequent treatment plan beyond year 10, and to describe the BMD trajectory among patients treated with more than 20 doses of denosumab.