Radium-223 for patients with metastatic castration-resistant prostate cancer with asymptomatic bone metastases progressing on first-line abiraterone acetate or enzalutamide: A single-arm phase II trial

Bone metastases; Metastatic castration-resistant prostate cancer Metástasis óseas; Cáncer de próstata metastásico resistente a la castración Metàstasis òssies; Càncer de pròstata resistent a la castració metastàtic Purpose The paper aims to evaluate the efficacy and safety of 223Ra in patients who progressed after first-line androgen deprivation therapy. Patients and methods EXCAAPE (NCT03002220) was a multicentre, single-arm, open-label, non-controlled phase IIa trial in 52 patients with metastatic castration-resistant prostate cancer and asymptomatic bone metastases who have progressed on abiraterone acetate or enzalutamide, up to six doses of 223Ra (55 kBq/kg of body weight per month). The primary end-point was radiographic progression-free survival (rPFS). Secondary end-points included rPFS based on androgen receptor splice variant 7 (AR-V7) expression in circulating tumour cells (CTCs), overall survival, and safety. Results Median rPFS was 5.5 months (95% CI 5.3–5.5). Median rPFS of patients with AR-V7(−) CTCs was longer than that of patients with AR-V7(+) CTCs (5.5 versus 2.2 months, respectively; P = 0.056). Median overall survival was 14.8 months (95% CI 11.2–not reached) and was significantly greater for AR-V7(−) patients than for AR-V7(+) patients (14.8 months versus 3.5 months, respectively; P < 0.01). 223Ra was well tolerated; anaemia and thrombocytopenia were the most common grade 3/4 adverse events (5.8% and 11.5%, respectively). Conclusions 223Ra seems to be a reasonable treatment for patients with metastatic castration-resistant prostate cancer and asymptomatic bone metastases progressing on novel hormonal therapy and had an acceptable safety profile. The study was conceived and designed by Joan Carles in collaboration with Medica Scientia Innovation Research (MEDSIR). MEDSIR, as legal sponsor of the study, is responsible for compliance with all clinical and regulatory procedures and adherence to the study protocol. MEDSIR had a role in study design, collection, management, analysis, and interpretation of the data and writing of the report. Bayer Inc. funded the study and provided 223Ra. The funder of the study had no role in data collection, management, data analysis, data interpretation, writing of the report, or decision to submit the manuscript for publication. All authors had full access to the data used to prepare the manuscript and participated in writing, editing, and/or critically reviewing the manuscript. The manuscript was written with editorial support from a medical writer, funded by MEDSIR. The corresponding author had final responsibility for the decision to submit for publication.