OBJECTIVES : Skeletal-related events (SREs) are common in patients with bone metastases (BM) from prostate cancer (PC). SREs have been associated with poor survival and increased costs. This study assessed the impact of SREs on post-BM anti-tumor therapy patterns in PC patients.

METHODS : In this retrospective cohort study, adults with ≥1 inpatient or ≥2 outpatient BM diagnoses on or after PC diagnosis between 01/01/2010 and 03/31/2016 were identified from the Truven Health MarketScan Commercial and Medicare databases. The index date was the first anti-tumor treatment (index treatment) date post-BM. All patients had ≥6-months of continuous enrollment pre- and post-index. SREs were identified during 6 month pre-index period and during index treatment post-BM. The impact of SREs on discontinuation of the index treatment post-BM, and progress to Next line of Therapy (NT) as a proxy for disease progression, were assessed, using Cox proportional hazard regression analysis, with occurrence of post-period SREs as a time-varying covariate.

RESULTS : A total of 1,534 patients met the study criteria, 214 (14%) of them had SREs pre-index. A total of 198 (12.9%) patients experienced SREs during index treatment post-BM [mean age: 70 (±10.4) years, mean comorbidity score: 8.2 (±2.1), visceral metastases: 12.6%, other metastases: 15.7%, index treatment use: 45.0% in the pre-index period]. Occurrence of SREs was statistically significantly (SS) associated with NT [Hazard ratio (HR): 1.25 {95% confidence interval (CI): 1.05-1.49}], but not with discontinuation [HR: 1.13 (95% CI: 0.96-1.34)]. Similar association between SREs and NT was observed in subgroup of patients (N=953) who were naïve to the index treatment prior to BM, with statistically non-significant (NS) HR: 1.21 (95% CI: 0.97-1.51).

CONCLUSIONS : Occurrence of SREs was associated with 13% (NS) higher chance of tumor therapy discontinuation and 25% (SS) higher likelihood of switching to next therapy, suggesting that SREs may indicate disease worsening in patients with BM from PC.