Background: Ra-223, an alpha-emitting pharmaceutical, significantly improved overall survival and was well tolerated in ALSYMPCA (Parker, NEJM2013). Long-term safety monitoring of Ra-223 is essential to build a complete safety profile and identify any association with secondary malignancies. Here we report adverse events (AEs) from ALSYMPCA patients (pts) ~1.5 y after last pt’s final injection (inj). Methods: All ALSYMPCA pts were to enter designated follow-up starting 4 wk after each pt’s last inj to 3 y after first inj. Only treatment (tx)-related AEs and specific diseases (acute myelogenous leukemia [AML], myelodysplastic syndrome [MDS], aplastic anemia [AA], primary bone cancer, primary cancer in other organs) were reported. Results: Of 921 pts (Ra-223, n = 614; pbo, n = 307), 574 entered designated ALSYMPCA follow-up (Ra-223, n = 406; pbo, n = 168). 335/406 (83%) Ra-223 pts and 119/168 (71%) pbo pts had 6 inj. Median follow-up time was 10.4 mo for Ra-223 pts and 7.6 mo for pbo pts. In the safety population, 25/404 (6%) Ra-223 pts and 8/167 (5%) pbo pts had 37 tx-related AEs (Table). Overall, myelosuppression incidence was ≤3%. No pts had AML, MDS, or primary bone cancer; 1 Ra-223 pt had AA, and 2 Ra-223 pts and 3 pbo pts had primary cancer in other organs (Table). Conclusions: Long-term follow-up of ~1.5 y after last pt’s final inj showed no new safety concerns or secondary malignancies related to Ra-223. Clinical trial information: NCT00699751.

* Safety population. ^†Gr 5.