Costs of skeletal-related events (SREs) in patients with metastatic castrate-resistant prostate cancer (mCRPC) treated with oral therapies.

Abstract

e16539 Background: SREs are associated with increased mortality and costs for mCRPC patients. The impact of mCRPC oral therapies on SREs is not well understood in the real world. This study examined the occurrence of and health care costs associated with SREs among mCRPC patients treated with abiraterone acetate + prednisone (ABI) or enzalutamide (ENZ). Methods: A retrospective study of a large national health claims database identified patients initiated on ABI or ENZ from 9/2012- 6/2015. Patients included had: ≥1 claim with prostate cancer diagnosis (ICD-9-CM 185.x) from 6 mo. pre- to 30 days post-index; ≥6 mo. pre- + ≥3 mo. post-index health plan enrollment. Index was date initiated on first oral therapy (ABI/ENZ). SREs (spinal cord compression, radiation to bone, pathological fracture, bone surgery) were assessed and health care cost calculated for patients with/without SREs in baseline/follow-up. Descriptive analyses and Cox proportional hazards examined SREs; generalized linear models assessed costs. Models adjusted for ABI/ENZ, age, region, baseline comorbidities, bone/brain/visceral metastases, docetaxel, and statin use. Results: The table below summarizes unadjusted results. Total all-cause per patient per month (PPPM) costs of 1,516 patients were highest for those with follow-up SREs. A significant difference in cost exists when comparing across all groups. Among patients without baseline SREs, adjusted analysis found greater hazards of follow-up SREs for baseline bone metastases (HR: 1.62, P = 0.003), baseline visceral metastases (HR: 1.68, P < 0.001), prior docetaxel (HR: 1.46, P = 0.004), and ENZ (vs. ABI) as first treatment (HR: 1.35, P = 0.013). Patients with follow-up SREs (with/without baseline SREs) had 19% higher adjusted costs compared to those without baseline or follow-up SREs (P < 0.001 each). Conclusions: SREs were common among mCRPC patients and associated with a significant financial burden. [Table: see text]