Symptomatic skeletal events and the use of bone health agents in a real-world treated metastatic castration resistant prostate cancer population: results from the CAPRI-study in the Netherlands

Abstract Background: Patients with metastatic castration resistant prostate cancer (mCRPC) are at risk of symptomatic skeletal events (SSE). Bone health agents (BHA, i.e. bisphosphonates and denosumab) and new life-prolonging drugs (LPDs) can delay SSEs. The aim of this study is to investigate the use of BHAs in relation to SSEs in treated real-world mCRPC population. Methods: We included patients from the CAPRI registry who were treated with at least one LPD and diagnosed with bone metastases prior to the start of first LPD (LPD1). Outcomes were SSEs (external beam radiation therapy (EBRT) to the bone, orthopaedic surgery, pathological fracture or spinal cord compression) and SSE-free survival (SSE-FS) since LPD1. Results: 1,923 patients were included with a median follow-up from LPD1 of 16.7 months. Fifty-two percent (n=996) started BHA prior or within four weeks after the start of LPD1 (early BHA). In total, 41% experienced at least one SSE. SSE incidence rate was 0.29 per patient year for patients without BHA and 0.27 for patients with early BHA. Median SSE-FS from LPD1 was 12.9 months. SSE-FS was longer in patients who started BHA early vs patients without BHA (13.2 vs 11.0 months, p=0.001). Conclusion: In a real-world population we observed an undertreatment with BHAs, although patients with early BHA use had lower incidence rates of SSEs and longer SSE-FS. This finding was irrespective of type of SSE and presence of risk factors. In addition to LPD treatment, timely initiation of BHAs is recommended in bone metastatic CRPC-patients with both pain and/or opioid use and prior SSE.