Clinical response to radium-223 dichloride in men with metastatic castrate-resistant prostate cancer

Purpose/Objective: Radium-223 prolongs survival and decreases symptomatic skeletal events in men with metastatic castrate-resistant prostate cancer and is indicated in patients with painful bone metastases. However, pain responses are rarely reported and often asked about by patients. Further, patients and their physicians are concerned about a lack of pain response portending a poor treatment response and may be inclined to change systemic therapies before completing 6 cycles. We evaluated the likelihood and time course of pain response, potential predictors of response, and its prognostic value in patients receiving radium-223. Materials and Methods: We reviewed the charts of patients who received radium-223 in our department. All patients were planned for 6 cycles with a prescribed dose of 50-55 kBq/kg at each administration. Pain scores, subjective response to pain, analgesic use, treatment toxicities, and laboratory values were recorded at each visit. Symptomatic skeletal events and survival were also recorded. Results: 48 patients received at least one cycle of radium-223 and 27 (56%) received all 6 planned cycles. Median survival from first treatment was 16.0 months (95% CI 8.9 to 19.2 months). 33% experienced at least one symptomatic skeletal event during or after treatment. 62.5% of men reported a decrease in pain from pre-treatment baseline. Of men with improved pain, 96% experienced an improvement before the third cycle. Pain relief was not associated with a decrease in ALK-P or PSA or improved survival. Conclusions: Approximately two-thirds of patients who undergo treatment with radium-223 will experience an improvement in pain and, if it occurs, it will most likely occur within the first two cycles. Patients should be counseled about this timeline and, if pain improvement isn't achieved, palliative radiation and oral analgesic readjustment should be considered. Pain response is not associated with survival and should not be used to evaluate the effectiveness of treatment. (C) 2018 American Society for Radiation Oncology. Published by Elsevier Inc. All rights reserved.