Prospective observational study to evaluate the persistence of treatment with denosumab in patients with bone metastases from solid tumors in routine clinical practice: final analysis.

Purpose: In the integrated analysis of phase III head-to-head trials in patients with advanced solid tumors, denosumab demonstrated superiority over zoledronic acid in preventing skeletal-related events (SREs). Regular and continued drug use (persistence) is a precondition of clinical efficacy; persistence in real-life is yet undetermined for denosumab.

Methods: This was a single-arm, prospective, observational, non-interventional study in 598 patients with bone metastases from breast, prostate, lung, or other solid tumors treated with denosumab every four weeks in real-world clinical practice in Austria, Czech Republic, Hungary, Slovakia, and Bulgaria. Persistence was defined as denosumab administration at ≤ 35-day intervals over 24 or 48 weeks, respectively.

Results: Previous SREs were found in 10.9% of patients. 62.6% were persistent over 24 weeks and 40.1% over 48 weeks. The Kaplan-Meier median (95% CI) time to non-persistence was 274.0 days (232.0, 316.0). The most frequent reason for non-persistence was delayed administration. There was a trend towards weaker analgesics over time, with approximately 60% of patients not requiring any analgesics. Serum calcium remained within the normal range throughout the study. Adjudicated osteonecrosis of the jaw was documented in three patients with an incidence per patient-year (95% CI) of 0.012 (0.004, 0.029).

Conclusions: Most patients received denosumab regularly once every four weeks over 24 weeks of treatment. Non-persistence was mainly due to delayed administration. The incidence of adverse drug reactions, especially of osteonecrosis of the jaw, was in line with expectations from previous studies.