First interim results of the radium-223 (Ra-223) REASSURE observational study: Analysis of patient (Pt) characteristics and safety by use of abiraterone and/or enzalutamide (Abi/Enza)

Abstract

Background: Ra-223 prolongs survival with a favorable safety profile in metastatic castration-resistant prostate cancer (mCRPC). The pivotal phase 3 ALSYMPCA trial had a relatively short 3-year follow-up and was conducted before availability of 2nd generation hormonal agents. The REASSURE study was designed to assess long-term safety (7 years follow-up) and conducted in an era when pts had access to other effective 1st line agents such as abi/enza. Method(s): REASSURE is a global, prospective, single-arm, observational study that enrolled pts with mCRPC with bone metastases planned to start Ra-223. Treatment decision was made independently before enrollment. We undertook a planned interim descriptive analysis of safety and drug completion based on prior or concomitant abi/ enza use. Result(s): REASSURE enrolled 1106 pts in N. America and Europe fromSep 2014 to Sep 2016. The interimanalysis included 583 pts who received >=1 Ra-223 dose (Table; median 7 months observation). Prior abi/enza use was reported in 168 (29%) and concomitant in 153 (26%) pts. Treatment-related adverse events (TRAEs) occurred in 37%: prior abi/enza 45%, no prior abi/enza 34%; concomitant abi/enza 29%, no concomitant abi/enza 40%. TRAEs weremost often gastrointestinal or hematological, with permanent discontinuation of Ra-223 in 6%: prior abi/enza 8%, no prior abi/ enza 5%; concomitant abi/enza 5%, no concomitant abi/enza 7%. Serious TRAEs (mostly hematologic) occurred in 4.5% leading to permanent Ra-223 discontinuation in 1.5%. (Table presented) Conclusion(s): Ra-223 has a good short-term safety profile when used in the routine clinical practice setting. Prior or concomitant abi/enza does not appear to increase TRAE incidence. Pts who had prior abi/enza had a lower rate of completing full Ra-223 dosing, perhaps reflecting poorer prognosis or more advanced disease as suggested by higher median PSA and LDH levels.