Impact of pre-treatment variables on the completion of 223radium-dichloride therapy in mCRPC patients with bone metastases.

ABSTRACT

INTRODUCTION: Radium-223 dichloride (223Ra) is an alpha-particle-emitter radiopharmaceutical, approved for metastatic castration-resistant prostate cancer (mCRPC) patients with symptomatic bone metastases and no visceral involvement. Its administration is based on a schedule of intravenous injection (55kBq/kg) every four weeks for up to six cycles. Because the biological effectiveness of 223Ra-therapy is dose-dependent, the main goal is to complete the entire treatment to achieve a better patient outcome. This study aims to identify potential pre-treatment variables that could impact on 223Ra-treatment completion and then be used to improve the clinical and supportive management of mCRPC patients. MATERIALS AND METHODS: 30 consecutive mCRPC patients (mean age 77 years old), who were admitted for Ra223-therapy at our Department from February 2016 to October 2018, were enrolled for the analysis. The population was grouped as patients who completed 223Ra-therapy (group Ra223-C) and patients who do not (group 223Ra-U). For each group, we analyzed the effects of potential pre-treatment variables (age, Gleason Score, tumor burden, "Time From Diagnosis To 223Ra therapy", type and number of previous treatments, hemoglobin level, Alkaline Phosphatase, Prostate Specific Antigen and pain) on the Ra223-therapy completion. Statistical analysis was performed to evaluate the association between the completion of 223Ra therapy and the variables examined. RESULTS: 16/30 (53%) patients were 223Ra-C, conversely 14/30 (47%) patients were 223Ra-U because of an early interrupted treatment. A statistically significant association was found only with tumor burden 68.7% of patients who completed 223-therapy had less than 20 bone metastases (χ2=4.821, p=0.028). CONCLUSION: Our preliminary analysis demonstrates that the high tumor burden represents the most important pre-treatment factor that could affect treatment completion and that needs to be considered before starting 223Ra-therapy to achieve a better outcome in mCRPC patients.