205PTreatment pattern and outcomes of radium-223 (Ra223) in metastatic castration resistant prostate cancer (mCRPC): Retrospective cohort analysis from Hong Kong

Abstract Background The real-life experience of radium-223 (Ra223) in metastatic castration-resistant prostate cancer (mCRPC) in Asia is limited. In recent ERA223 study, the post-treatment osteoporotic fracture risk was unexpectedly found elevated when Ra223 was given in addition to abiraterone/prednisone in mCRPC, raising a concern of long-term bone safety with Ra223. Methods Hospital records of consecutive patients with mCRPC treated with Ra223 in 5 Hong Kong public hospitals from Nov 2015 to Oct 2018 were retrieved for the analysis of treatment pattern and clinical outcomes. Results We identified 42 men with bony mCRPC (median age: 73; 78.6% ECOG PS 0/1; 61.9% with bone pain; 50% lymphadenopathy; 14.3% visceral metastases) who received at least 1 dose of Ra233 (median 6, IRQ: 4-6). Median follow-up was 8.8 months. Ra223 was administered at a median of 3rd line setting (IQR: 2nd to 4th line) with 88.1% and 35.7% having prior androgen-receptor axis-targeted agents (ARTAs, i.e. abiraterone and enzalutamide) and docetaxel. Ra223 was used concomitantly with ARTAs and bone health agents at 23.8% and 45.2%, respectively. 64.5% of patients had subsequent therapies (16.7% chemotherapy; 42.9% ARTAs). Median time to PSA progression was 3.6 months (IQR: 3.5-4.5) and 48.6% (18/37) had 30% drop of ALP after 3rd injection. 26.9% (7/26) with bone pain requiring analgesics had symptomatic improvement but 15% had worsened pain. 66.7% of patients were free from symptomatic skeletal event (SSE), with 6-month and 1-year SSE rates being 11.9% and 26.2%. The median OS was 18.2 months (95%CI: 4.6-31.9) and was longer for patients who received >4 injections (27.7 vs 7.8 months, p = 0.015). The most common AEs were anemia (67%), fatigue (36%), bone pain (33%), thrombocytopenia (26%) and neutropenia (19%). Treatment discontinuation due to AEs was 8%. Non-osteoporotic fracture was seen in 3 patients (2 pathological and 1 traumatic). Conclusions Later line use of Ra223 was a common real-life practice. Efficacy and tolerability with Ra223 remains favorable in heavily-pretreated mCRPC, despite higher rate of hematological AE was seen. With nearly ¼ patients with concomitant ARTAs, osteoporotic fracture was not seen in this cohort. Legal entity responsible for the study the authors. Funding Has not received any funding. Disclosure All authors have declared no conflicts of interest.