Understanding the Guideline-Discordant Use of Bone Modifying Agents in Prostate Cancer

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PROJECT SUMMARY Bone-modifying agents (BMAs) can improve quality-of-life in metastatic prostate cancer. The BMAs zoledronic acid and denosumab prevent bone fractures among men with metastatic, castration-resistant prostate cancer (mCRPC), resulting in reduced pain and improved function. However, BMAs can cause serious side effects. Because BMAs do not prevent fractures among men with metastatic, castration-sensitive prostate cancer (mCSPC), the risk/benefit balance does not support BMA use for these patients. For these reasons, the National Comprehensive Cancer Network Guidelines recommend for the use of BMAs in mCRPC, and against their use in mCSPC. Patient outcomes may therefore be adversely affected by both BMA underuse among patients with mCRPC and by overuse among patients with mCSPC. However, little is known about the real- world use of BMAs in prostate cancer. To determine whether BMA underuse and/or overuse are significant problems, the utilization patterns of BMAs for prostate cancer must first be understood. BMA drugs also have important differences in value – benefits relative to financial cost. Zoledronic acid is cost-effective, but denosumab, which is much more expensive, is not. The use of denosumab instead of zoledronic acid may therefore result in avoidable costs to patients and the health system. To address these knowledge gaps, we propose to describe real-world use of BMAs in prostate cancer using SEER-Medicare data. We will identify two key patient groups: those with mCRPC, among whom BMA use is recommended, and those with mCSPC, among whom BMA use is discouraged and would constitute overuse. We will determine the prevalence of BMA therapy within each group and characterize the patient and provider factors associated with underuse and overuse. We will also assess whether increased denosumab use has resulted in excess financial costs to patients or to Medicare. Aim 1: Measure the prevalence of underuse and overuse of bone-modifying agents in prostate cancer. To measure potential underuse, we will use SEER-Medicare data to identify patients with mCRPC and determine their receipt of BMAs (Aim 1A). To measure overuse (Aim 1B), we will identify patients newly diagnosed with mCSPC and determine receipt of BMAs. Aim 2: Identify and describe patient and provider factors associated with underuse and overuse of bone-modifying agents. We will use SEER-Medicare data to identify key patient socioeconomic factors and provider organizational factors associated with BMA underuse (Aim 2A) and overuse (Aim 2B). Aim 3: Evaluate changes in utilization of denosumab and associated costs. We will assess temporal trends in the relative use of denosumab vs. zoledronic acid (Aim 3A) and estimate resulting costs to patients and to Medicare (Aim 3B). Impact: This study will increase our understanding of BMA utilization in prostate cancer. Study results may lead to future interventional work to improve prostate cancer outcomes by reducing BMA underuse and overuse.