Single-centre Experience of Use of Radium 223 with Clinical Outcomes Based on Number of Cycles and Bone Marrow Toxicity

Background: Bone is the most common site of metastatic disease in advanced prostate cancer. Radium-223 (²²³Ra) is a calcium-mimetic alpha-particle emitter, which has been shown to have activity in prostate cancer with clinical benefit in patients with symptomatic bone metastasis. The recommended schedule is six cycles of ²²³Ra, 5 kBq/kg, at 4-weekly intervals. Although previous studies have assessed clinical outcomes in patients who received six cycles of Ra²²³, there is very little information about outcomes of patients receiving fewer courses of treatment. Patients and Methods: Patients with hormone-refractory metastatic prostate cancer treated from May 2014 to August 2016 were included in this retrospective study. A total of 113 patients were identified with a median age of 76 (range=52-92) years. The median number of cycles administered was 5 (range=1-6) with 54 (48%) completing six cycles of treatment. Eighty-five patients (75%) received ²²³Ra prior to docetaxel chemotherapy and 28 (25%) received it after receiving docetaxel. Results: Eleven patients developed grade 2/3 thrombocytopenia, and none of these received further ²²³Ra. Only 25% of patients who had a haemoglobin level of 10 g/dl or below at the start of the treatment were able to complete six courses of ²²³Ra. Of the patients who completed fewer than six cycles of ²²³Ra (1-5 cycles), the survival was 121 days, compared to 398 days in men who received six cycles (odds ratio(OR)=4.767, 95% confidence internal(CI)=1.07-21.25; p=0.0005). Conclusion: Careful selection of patients is essential to obtain good clinical outcomes from ²²³Ra therapy. When fewer than six cycles were delivered then a beneficial survival effect was not seen.

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