Background: Ra-223, an alpha-emitting radiopharmaceutical, significantly improved overall survival and was well tolerated in ALSYMPCA (Parker, NEJM2013). Ra-223 long-term safety monitoring is essential to a complete safety profile. Here we report adverse events (AEs) from ALSYMPCA pts 3 y after last pt’s first injection (inj). Methods: All pts were to enter designated follow-up from 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), 575 entered follow-up (Ra-223, n = 407; pbo, n = 168). 336/407 (83%) Ra-223 pts and 119/168 (71%) pbo pts had 6 inj. Median follow-up time was 10.3 mo for Ra-223 pts and 7.6 mo for pbo pts. In the safety population, 27/405 (7%) Ra-223 pts and 8/167 (5%) pbo pts had 42 tx-related AEs (Table). Myelosuppression incidence was ≤ 3%. No pts had AML, MDS, or primary bone cancer; 1 Ra-223 pt had AA, and 3 Ra-223 and 3 pbo pts had primary cancer in other organs (Table). Conclusions: Long-term follow-up 3 y after last pt’s first inj showed no new safety concerns or secondary malignancies related to Ra-223. Clinical trial information: NCT00699751

*Safety population who entered follow-up. ^†Gr 5. ‡Missing CTC grade.