Osteoclast Inhibitor Treatment Among Men with Metastatic Castration-resistant Prostate Cancer

Background: National Comprehensive Cancer Network guidelines recommend monthly osteoclast inhibitor treatment (OIT) in men with metastatic castration-resistant prostate cancer (mCRPC) to prevent skeletal related events (SREs). We assessed adherence to guidelines by quantifying treatment for SRE prevention in a population-based cohort of men with mCRPC.

Methods: Using Surveillance, Epidemiology, and End Results-Medicare data, we identified men aged >65 with prostate cancer as a primary cause of death during 2006-2010. We assessed OIT during a 12-month period between 15 and 3 months before death and used multivariable negative binomial regression to identify factors associated with treatment.

Results: Among 9,634 men who died of prostate cancer, 22% received ≥ 1 OIT, and use increased slightly over time. Men age 75-84 and ≥ 85 were less likely than younger men to be treated (IRR 0.63, 95% CI 0.49-0.78 and IRR 0.34, 95% CI 0.17-0.50, respectively). African American men were less likely than white men to receive OIT (IRR 0.75, 95% CI 0.54-0.95), as were men from areas with lower median income (P=0.014). Compared with men seeing a urologist only, men seeing a medical oncologist and a urologist (IRR 2.52, 95% CI 2.36-2.68) or a medical oncologist alone (IRR 3.82, 95% CI 3.54-4.09) had higher incidence rates of treatment.

Conclusions: Fewer than a quarter of American men dying of prostate cancer received recommended treatment to prevent SREs within the final year of their lives, with particularly low rates of treatment among older men, African American men, and those living in areas with low median income. Visits with a medical oncologist were associated with increased use. Further evaluation of these disparities by age, race and socioeconomic status are necessary to identify interventions to reduce them.