Persistence with Denosumab in Women at High Risk of Fracture in Bulgaria

Introduction: Post-menopausal women with osteoporosis > 70 years of age at high risk of fracture urgently require treatment for fracture prevention. Moreover, persistence with osteoporosis therapy is critical for real-world effectiveness. We estimated persistence with denosumab in older women at high fracture risk in clinical practice in Bulgaria.

Methods: Eligible participants were post-menopausal women, > 70 years of age, diagnosed with osteoporosis (T-score ≤ - 2.5) and at high risk of fracture (≥ 3% for hip and ≥ 20% for major osteoporotic fracture) who received at least one denosumab injection before enrollment. Planned follow-up was 24 months. The primary endpoint was persistence to denosumab at 12, 18, and 24 months (defined as receiving all denosumab injections within 6 months ± 60 days of the previous injection).

Results: 250 women were enrolled across 12 Bulgarian endocrinology/rheumatology practices; median follow up, 736 days. Mean (SD) age was 75.8 (4.2) years; mean (SD) FRAX^® was 13.1 (8.6) for hip and 26.1 (9.5) for major osteoporotic fracture; 47 (18.8%) women had prior osteoporosis therapy and 104 (41.6%) had prior fracture. Denosumab persistence was high: 98.0%, 92.4%, and 84.4% at 12, 18, and 24 months, respectively. A total of 42 (16.8%) women discontinued denosumab during follow-up, mostly for financial reasons [25/42 (59.5%)] or loss to follow-up [8/42 (19.0%)]. After 24 months of denosumab treatment, BMD T-score improvement to the range of osteopenia (- 2.5 ≤ T < - 1.5) was achieved by 42.4% at the femoral neck, 23.6% at the lumbar spine, and 49.2% at the total hip; complete recovery (T-score ≥ - 1.5) was observed in 9.0%, 26.4%, and 23.0% respectively. New fracture was reported in 5 patients (2%).

Conclusions: Even in an elderly population, persistence with denosumab was high despite the challenge imposed by the 50% co-pay in Bulgaria.

Trial registration: Bulgarian Drug Agency, №HИП-0009 (registered 28.06.2017); Central Ethics Commission: №КИ-41 (registered 16.05.2017).