Real-World Safety and Effectiveness of Radium-223 in Patients with Metastatic Castration-Resistant Prostate Cancer: Final Analysis of the RAPIT Study.

Abstract

BackgroundRadium-223 dichloride (radium-223) is an α-emitting radionuclide approved for treating metastatic castration-resistant prostate cancer (mCRPC) with symptomatic bone metastases and no visceral disease.ObjectiveAlthough efficacy and safety were established in pivotal trials, real-world evidence in Asian populations, particularly Taiwan, remains limited. Here we report the final analysis of the observational RAdium-223 dichloride in routine clinical Practice settings In Taiwan (RAPIT) study.MethodsThis prospective, multicenter, single-arm, noninterventional study included patients with mCRPC with symptomatic bone metastases receiving radium-223 in clinical practice in Taiwan. The primary objective was to evaluate safety, including treatment-emergent and drug-related adverse events and long-term safety. Effectiveness outcomes were secondary endpoints.ResultsA total of 224 patients were enrolled; most had ≤ 20 bone metastases (69.2%) and received five or six radium-223 injections (68.8%). Radium-223 was most often a second-line (47.7%) or later-line (29.1%) therapy. For second-line patients, the most common first-line treatment was an androgen receptor pathway inhibitor (ARPI). Among patients receiving radium-223 third line, first- to second-line treatment sequences included ARPI-docetaxel (38.9%), docetaxel-ARPI (37.0%), and ARPI-ARPI (24.1%). Most patients (67%) received no further therapies after their last radium-223 dose. Radium-223-related any-grade and serious adverse events occurred in 13.8% and 3.1% of patients, respectively. Median overall survival was 21.93 months (95% CI 16.33, not reached).ConclusionsThe RAPIT study demonstrated an acceptable safety profile and consistent effectiveness of radium-223 in a real-world cohort of Taiwanese patients with mCRPC and bone metastases. Patients treated earlier in their course or completing five to six injections had longer overall survival in this cohort, suggesting potential benefit in appropriately selected patients.Clinical trial registrationClinicalTrials.gov, NCT04232761.