A Single-center Retrospective Analysis of the Effect of Radium-223 (Xofigo) on Pancytopenia in Patients with Metastatic Castration-resistant Prostate Cancer.

Introduction Radium-223 (Xofigo, Bayer Pharmaceuticals Inc., Whippany, NJ) has been shown to increase overall survival in patients with metastatic castration-resistant prostate cancer (mCRPC), via the phase 3 ALpharadin in SYMPtomatic Prostate CAncer (ASLYMPCA) study. Hematologic side effects of radium-223 included all-grade anemia in 31% of the patients, thrombocytopenia in 12%, and neutropenia in 5%, and persistent pancytopenia noted in 2%. However, the incidence seen in our institutional clinical practice is higher than that reported in the literature. Methods A retrospective analysis was performed by analyzing patients with mCRPC who received Xofigo at the University of Florida Health Shands Hospital (UF Health Shands) in a three-year span. Data collected included complete blood count (CBC), ECOG (Eastern Cooperative Oncology Group) functional status, kidney and liver function, evidence of bony disease on imaging, prior chemotherapy regimens, total radiation dose, and prostate-specific antigen (PSA).  Results Twenty-three patients received Xofigo at UF Health, and one was lost to follow-up. Sixteen patients (73%) completed the full course (six doses) of Xofigo, while six did not. Ten patients (45%) developed pancytopenia, with two recovering counts within eight months while the other eight had persistent cytopenias (six of which were transfusion-dependent). Older age and higher ECOG score correlated with increased risk of pancytopenia. In addition, a higher percentage of patients who received prior radiation therapy were more likely to develop pancytopenia (90% vs 75%). Conclusions  We found a higher rate of Xofigo-induced pancytopenia in our patient population than the 2% reported in the literature, albeit with a limited sample size, This may influence clinical decision making in the treatment of mCRPC, as pancytopenia may preclude patients from other survival-prolonging therapies. Factors such as age, functional status, and prior radiation therapy have to be considered prior to Xofigo treatment.