Introduction: Romosozumab, a monoclonal anti-sclerostin antibody, is an osteoporosis drug available in the Netherlands since 2021 indicated for patients with a very high fracture risk. Due to its recent introduction, few studies have assessed its efficacy and adverse events in clinical practice. This study is the first to report the real-world effect on bone mineral density of romosozumab in the Netherlands. 

Methods: This retrospective observational cohort study included osteoporosis patients treated with romosozumab during 2021 and 2022 in the Leiden University Medical Center and Jan van Goyen Medical Center in the Netherlands and assessed bone mineral density (BMD) changes as measured with dual energy x-ray absorptiometry (DXA) after one year of treatment. Subgroup analysis was performed in patients with or without previous osteoporosis treatment. Adverse events were extracted from the patient charts.

Results: 57 consecutive patients (median age 70 years IQR 13, 90% female) were included in the study. After 12 months of romosozumab treatment, BMD in the total cohort increased with 12.0% at the lumbar spine, and 5.4% at the left hip (femoral neck; P<0.001 for all changes). Although the BMD increase was less in patients pretreated with osteoporosis medications in comparison to treatment naïve patients, the improvement remained statistically significant. Romosozumab was generally well tolerated; local skin reactions at the injection site were the most frequently reported side effect. One subject discontinued treatment due to loss of apetite and weight loss. There were four non-responders on BMD of the lumbal spine, and five new fractures did occur.

Conclusion: In a Dutch real-world setting, 12 months of treatment with romosozumab was highly effective in increasing BMD in patients with and without previous osteoporosis treatment, comparable to the clinical trial setting. The treatment was well tolerated without major adverse events. To strengthen our findings, data are currently extended with VieCurie Medical Center and the Amsterdam University Medical Centers.