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

Abstract

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 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. 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). 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.