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

Several life-prolonging therapies for metastatic castration-resistant prostate cancer (mCRPC) are available, including radium-223 dichloride (Ra-223), which was approved based on phase 3 data demonstrating improved overall survival (OS) and a favorable safety profile. To date, real-world evidence for Ra-223 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. Ra-223 was prescribed as part of routine practice by investigators. Patients with prior Ra-223 treatment were excluded. The primary objective was to assess Ra-223 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. Ra-223 was first- or second-line therapy in 23.2% and 47.7% of patients, respectively. The total proportion of patients who received 5-6 Ra-223 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-na & iuml;ve patients (61.9%) completed the 6-cycle Ra-223 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 Ra-223-related adverse events. Median OS was 15.7 months (95% confidence interval 12.13-19.51); patients receiving 5-6 Ra-223 injections and earlier Ra-223 use had longer OS than those receiving fewer injections and later Ra-223 use. Ra-223 provides a well-tolerated and effective treatment for Taiwanese patients with mCRPC and bone metastases.