Bone-targeting agents in major solid tumour metastases: A multinational cohort study

Objective To describe the epidemiology, clinical characteristics and utilisation patterns of bone-targeting agents (BTAs) in patients with bone metastases from breast, prostate and lung cancer. Methods This is a multinational retrospective cohort study including patients with three major solid tumours (breast, prostate and lung cancer) and newly initiated on BTAs (ie, denosumab, zoledronic acid and pamidronate). Records were retrieved from nationwide health databases from Hong Kong and Taiwan (HK and TW: 2013-2017) and Korea (KR: 2012-2016). Descriptive analyses included the annual incidence rates of bone metastases and the cumulative incidence curves of BTA initiation. We used Sankey diagrams to visualise the dynamic BTA utilisation patterns. Results The annual incidence rate of bone metastases ranged from 3.5% to 4.5% in TW, from 9.6% to 10.3% in HK and from 2.9% to 3.8% in KR. We identified 14.1% (5127), 9.3% (883) and 9.4% (4800) of patients with bone metastases newly initiated on BTAs in TW, HK and KR, respectively. The most frequently used BTA in TW (67.1%) and HK (51.9%) was denosumab, while in KR (84.8%) it was zoledronic acid. Sankey diagrams indicated the proportion of patients remaining on denosumab was highest in TW and HK, while it was zoledronic acid in KR. Specifically, in TW, patients who were on bisphosphonates or had discontinued treatment frequently switched to or reinitiated denosumab. Conclusions We found the rate of BTA utilisation remained low across all sites and tumour types in recent years. The dynamic utilisation patterns of BTAs provide better understanding of the treatment landscape for future evaluation of associated outcomes of patients.