Investigation of the safety of Radium-223 chloride in combination with external beam radiotherapy for bone metastases of prostate cancer.

This study aimed to investigate the safety of combining radium-223 chloride (Ra-223) therapy with external beam radiation therapy (EBRT) for patients with multiple bone metastases from castration-resistant prostate cancer (CRPC), including lesions requiring urgent treatment such as those causing neurological symptoms due to spinal cord compression. We retrospectively analyzed data from patients with CRPC and bone metastases treated with Ra-223 therapy at our hospital between September 1, 2018, and December 31, 2023. Adverse events were evaluated using the Common Terminology Criteria for Adverse Events version 4.0. Of the 23 patients referred, data from 17 were included; 8 received concurrent Ra-223 therapy and EBRT, whereas others received only Ra-223 therapy. The median follow-up period was 20 months. Grade (G) 2 or higher adverse events occurred in seven patients (41.2%), and G 3 or higher in 2 (11.7%). None of the patients who received EBRT with fields involving the gastrointestinal tract experienced diarrhea, constipation, bleeding, perforation, or obstruction. Ra-223 therapy with EBRT did not increase adverse events compared with studies of Ra-223 therapy without EBRT. One case of G 5 Pneumocystis carinii pneumonia, likely because of steroid use for neurological symptoms and the patient's underlying diabetes mellitus, was noted. The effects of EBRT cannot be entirely excluded, so minimizing field size and dose is recommended when combining Ra-223 therapy and EBRT. Our findings indicate that concurrent Ra-223 therapy and EBRT could be safe for managing patients with symptomatic bone metastases and castration-resistant prostate cancer who require specialized treatment, provided sufficient attention is given to the field and the prescribed dose.