Real‐world safety and effectiveness of radium‐223 in patients with metastatic castration‐resistant prostate cancer: Interim analyses of the prospective, observational RAPIT study

Abstract Several life‐prolonging therapies for metastatic castration‐resistant prostate cancer (mCRPC) are available, including radium‐223 dichloride ( 223 Ra), which was approved based on phase 3 data demonstrating improved overall survival (OS) and a favorable safety profile. To date, real‐world evidence for 223 Ra use in Taiwan is from three studies of <50 patients. This observational study (NCT04232761) enrolled male patients with histologically/cytologically confirmed mCRPC with bone metastases from centers across Taiwan. 223 Ra was prescribed as part of routine practice by investigators. Patients with prior 223 Ra treatment were excluded. The primary objective was to assess 223 Ra safety; secondary objectives evaluated efficacy parameters, including OS. Overall, 224 patients were enrolled. Most patients had an Eastern Cooperative Oncology Group performance status of 0/1 (79.0%) and ≤20 bone metastases (69.2%); no patients had visceral metastases. 223 Ra was first‐ or second‐line therapy in 23.2% and 47.7% of patients, respectively. The total proportion of patients who received 5–6 223 Ra cycles was 68.8%; this proportion was greater with first‐line use (84.3%) than second‐ (65.7%) or third‐/fourth‐line use (64.1%). More chemotherapy‐naïve patients (61.9%) completed the 6‐cycle 223 Ra treatment than chemotherapy‐exposed patients (56.7%). Any‐grade treatment‐emergent adverse events (TEAEs) and serious TEAEs occurred in 54.0% and 28.6% of patients, respectively, while 12% experienced 223 Ra‐related adverse events. Median OS was 15.7 months (95% confidence interval 12.13–19.51); patients receiving 5–6 223 Ra injections and earlier 223 Ra use had longer OS than those receiving fewer injections and later 223 Ra use. 223 Ra provides a well‐tolerated and effective treatment for Taiwanese patients with mCRPC and bone metastases.