Background: Radium 223 (Ra-223) is a FDA and EMA approved alpha particle radiopharmaceutical used to treat men with metastatic castrate resistant prostate cancer (mCRPC) with symptomatic bone metastasis. In view of emerging systemic options, new EMA 2018 licence indication is for 3^rd line onwards. We aim to evaluate the impact of systemic therapy sequencing on survival outcomes from a heterogeneous cohort of 228 patients treated with Ra-223 in a single UK centre. Methods: We prospectively collected data from 228 men underwent Ra-223 therapy for mCRPC between April 2014 and August 2018. Survival outcomes in relation to sequence of systemic treatment used prior to Ra-223 were analysed. Results: Medium age = 72 (51-87) years. Most patients (n = 142, 69%) received at least one systemic agent prior to Ra-223: docetaxel and/or cabaxitaxel chemotherapy (n = 60, 29%), abiraterone (n = 62, 30.1%) and enzalutamide (n = 67, 32.5%) in various sequences. No patients received concurrent Ra-223 /systemic treatment other than LHRH analogue. Key findings are summarized in table below. Conclusions: Our data demonstrated better survival trend in patients who received Ra-223 early. Patients who received prior chemotherapy have worse survival compared with those who were chemo-naïve likely due to bone marrow depletion. Ra-223 should not be offered to patients who have already had both cabaxitaxel and docetaxel as their medium survival is too poor to justify a treatment which takes 6 months to complete.

PS = Performance Status, Hb = Haemoglobin, Plt = platelet, End = end of treatment.