OBJECTIVES: Metastatic lung, breast, and prostate cancer patients (MLBPC) experience skeletal related events (SREs), which significantly decrease survival. Denosumab (DS) and Zoledronic acid (ZA) are recommended for these patients to prevent such SREs. However, there is a lack of evidence in the patterns and predictors of real-world initiation of DS versus ZA in older MLBPC patients in the United States. The objective of this study was to examine the trends and factors associated with DS or ZA initiation among older MLBPC patients in the US.

METHODS: We used the Surveillance, Epidemiology, and End Results (SEER)-linked Medicare data to identify patients diagnosed with MLBPC between 2012 and 2017 who initiated DS/ZA treatment within 12 months of cancer diagnosis. Demographics, healthcare utilization, comorbidities, disease and treatment attributes of new users were evaluated. Trends in treatment initiation were assessed using Cochran-Armitage tests among all MLBPC patients and by cancer type. T-tests, Chi-squared tests and multiple logistic regressions were employed to identify factors influencing the choice between DS and ZA initiation.

RESULTS: In 2012-2017, DS initiation trends increased across all individual cancer cohorts as well as the overall MLBPC sample, while ZA initiation notably decreased in the metastatic breast cancer and MLBPC cohorts (all P<0.0001). Patients more likely to initiate DS over ZA were older at diagnosis, Hispanic, single, eligible for low-income subsidies, urban residents, had multiple comorbidities, impaired renal function, and prior chemotherapy use.

CONCLUSIONS: There are significant differences between the trends in DS and ZA initiation as well as in the factors affecting initiation among MLBPC patients.