Fracture rates in radium223 (Ra223) treated mCRPC patients (pts): A real-world analysis in 177 pts treated at a single community center 2010-2018.

Abstract

41 Background: Ra223 was FDA approved 5/15/13 as a life extending therapy in conjunction with Standard of Care (SOC) agents for mCRPC in the ALSYMPCA trial. However, agents such as abiraterone (abi) and enzalutamide (enza) were not part of the SOC regimens allowed during conduct of ALSYMPCA. Phase 2 and expanded access programs (EAPs) suggested enhanced activity when abi or enza were given with Ra223. A phase 3 trial (ERA223 Smith et al. Lancet Oncology 2019) comparing Ra223 +/-abi showed an increased fracture (Fx) rate (29% vs 11%) and no survival advantage for the combo, leading to regulatory restrictions on abi and Ra223 combination therapy. However, only 41% of pts in ERA223 received bone health agents (BHAs). This center participated in ALSYMPCA and in the US EAP and based on those data, BHAs were consistently administered monthly during Ra223. The Fx rate in ERA223 did not mirror our clinical experience and thus our institutional Ra223 database was reviewed. Methods: Cohort analysis of pts who received Ra223 for mCRPC under the supervision of NJV. Follow-up was until date of death or last data entry. Results: 177 pts received Ra223 between 11/2010 and 8/2018. Median age 73 at 1st Ra223 (range 40-93); Median PSA (15.8- at 1st Ra223 (range 0.1-1952); Demographics-AA-10, C-130, Asian-9, unspecified- 28; Median Gleason score 8, Median Alk Phos 95 at 1st Ra233 (range 25-1515). Median mos of prior ADT 23 (range 0-247mos). Pts on concurrent abi + pred + Ra223 69 (39%); abi + Ra223 7 (4%); abi + pred prior to Ra223 54 (31%); abi prior to Ra223 4 (2.3%). Enza + Ra223 51 (29%); enza prior to Ra223 39 (22%). 164 pts (93%) were on BHAs before or during Ra223 (denosumab 86 concurrent vs zoledronic acid 64 concurrent). 10 pts (5.6%) had Fxs reported after the start of Ra223 (4 with concurrent abi, 3 with concurrent enza, 3 on Ra 223 w/o concurrent abi or enza; 8/10 Fxs occurred while on BHA’s). Conclusions: In contrast to the ERA223 study where 11-29% of pts experienced Fxs, this real-world experience with Ra223 in which 164/177 pts (93%) received BHAs before or during Ra223 saw a 5.6% Fx rate. When Ra223 was given concurrently with abi or enza and BHAs, the Fx rate was 6/177 (3.4%).