An Observational Study of Concomitant Use of Emerging Therapies and Denosumab or Zoledronic Acid in Prostate Cancer

Purpose: This observational study of oncologic clinical practices was designed to describe real-world patterns of use of emerging therapies (abiraterone acetate, cabazitaxel, enzalutamide, radium-223, sipuleucel-T) in patients with castration-resistant prostate cancer and to characterize their concomitant use with denosumab or zoledronic acid.

Methods: A retrospective cohort study was conducted using a database of electronic health records from oncology practices across the United States. Eligible patients had a diagnosis of prostate cancer (International Classification of Diseases, Ninth Revision [ICD-9] code 185/International Classification of Diseases, Tenth Revision [ICD-10] code C61) before or concurrent with a visit between January 1, 2013, and December 31, 2015; follow-up was performed through June 30, 2016. From this population, we identified those who received an emerging therapy and a subset who also received denosumab or zoledronic acid.

Findings: A total of 71,606 men met the eligibility criteria, and 5131 (7%) received emerging therapy. In the emerging therapy cohort (at the time of the first use), median age was 75 years, median prostate-specific antigen value was 22.7 ng/mL, 56% had bone metastases, and 80% were docetaxel naive. Abiraterone and enzalutamide were the most commonly used first emerging therapies (52% and 31%, respectively), followed by sipuleucel-T (9%), cabazitaxel (5%), and radium-223 (1.5%). Of the emerging therapy cohort, 3121 patients (61%) received concomitant denosumab (70%) or zoledronic acid (35%); 5% received both.

Implications: Among patients with prostate cancer treated in the United States, most of those treated with an emerging therapy between 2013 and 2015 also received denosumab or zoledronic acid, suggesting that the concomitant use of these therapy types is currently a common practice. Use of denosumab or zoledronic acid was higher in patients with verified bone metastases.