AIM: Estimate the effect of Radium-223 (Ra-223) on the incidence of bone fractures, prostate cancer death, and all-cause death compared with other standard treatments for metastatic, castration-resistant prostate cancer (mCRPC).
METHODS: Using a cohort design, we estimated the effect of Ra-223 on the risk of bone fractures, all-cause and prostate cancer–specific mortality across different lines of treatment for mCRPC using Prostate Cancer data Base Sweden (2013-2018). The comparator group comprised other standard treatments for mCRPC. We used 36-month risk differences and hazard ratios (HRs) as effect estimates.
RESULTS: The number of eligible individuals was 635, 453, 262, and 84 for the first-, second-, third-, and fourth-line cohorts, respectively. When compared Ra-223 to other standard treatments, the difference in the 36-month risk of fracture was 6% (95% confidence interval [CI], −7% to 18%) in the first-line cohort (n=635) and 8% (95% CI, −7% to 18%) in the second-line cohort (n=453). The number of fractures in the third-/fourth-line cohorts was too small for an adjusted comparison. The difference in 36-month mortality was higher in the first-line cohort 13% (95% CI, −3% to 31%), but lower in the second- and third-/fourth-line cohorts−8% (95% CI, −23% to 7%) and −14% (95% CI, −21% to 16%) respectively. Most deaths were due to prostate cancer
CONCLUSION: Results suggest that the difference in the risk of fractures is small, if any. A difference in the risk of mortality may be present in first-line treatment, but a decreased risk of mortality was observed in second and later lines of treatment. The results on mortality need to be considered in the context of potential unmeasured or residual confounding.
