Patterns of care and economic consequences of using bone-targeted agents for castration-sensitive prostate cancer patients with bone metastases to prevent skeletal-related events in Switzerland - the SAKK 95/16 prostate study.

Background: International guidelines state that bone-targeted agents such as denosumab or zoledronic acid at doses used for bone metastasis are not indicated for patients with metastatic castration-sensitive prostate cancer (mCSPC) with bone metastases. Whereas denosumab has never been studied in this patient population, zoledronic acid has been shown to be ineffective in decreasing the risk for skeletal-related events. This study estimates the prevalence and economic consequences of real-world use of bone-targeted agents for mCSPC patients in Switzerland.

Methods: To estimate the frequency of bone-targeted agent administration and skeletal-related events, data from a non-interventional, cross-sectional survey involving oncologists across Switzerland (SAKK 95/16) was combined with data from the Swiss National Institute for Cancer Epidemiology and Registration (NICER). Economic parameters were calculated from the perspective of the healthcare system over the median time to prostate-specific antigen (PSA) progression for the extrapolated patient group, using data from NICER. The cost calculation covered costs for bone-targeted agents, their administration and skeletal-related events. The time to PSA progression (33.2 months), as well as the probability and cost of skeletal-related events were derived from the literature.

Results: The survey was answered by 86 physicians treating 417 patients, of whom 106 (25.4%) had prostate cancer, with 36 (34.0%) of these mCSPC. The majority of mCSPC patients (52.8%, n = 19) received bone-targeted agents monthly. Denosumab was the treatment of choice in 84.2% of patients (n = 16). Extrapolation using data from NICER indicated that 568 mCSPC patients may be treated with bone-targeted agents at doses used for bone metastasis  every year in Switzerland, leading to estimated total costs of more than CHF 8.3 million over 33.2 months. Because of its more frequent prescription and higher price, it appears that almost 93% of the total costs can be attributed to denosumab. For both denosumab and zoledronic acid, the most expensive components were the cost of administration and the drug cost, making up more than 90% of the total costs, with the rest being costs of skeletal-related events.

Conclusions: This study found that the administration of bone-targeted agents in doses used for bone-metastatic diseases to prevent skeletal-related events is frequent in the setting of mCSPC and results in significant costs for the healthcare system.