SAN FRANCISCO—Radium-223 dichloride remains an “effective and well-tolerated” treatment for men with castration-resistant prostate cancer (CRPC) and bone metastases, long-term safety follow-up results from the phase 3 ALSYMPCA study presented at the 2014 Genitourinary Cancers Symposium have shown.
“No major safety issues were identified within approximately 1.5 years after treatment in the ALSYMPCA safety population,” noted Sten Nilsson, MD, PhD, a professor of oncology at the Karolinska University Hospital, Stockholm, Sweden.
The ALSYMPCA study compared radium-223 plus best standard of care versus placebo plus best standard of care in 922 patients worldwide who had progressive CRPC with two or more symptomatic bone metastases and no known visceral metastases. Patients were randomly assigned 2:1 to six injections of radium-223 (50 kBq/kgintravenously, every 4 weeks) or matching placebo. Results showed radium-223 significantly improved overall survival by 3.6 months compared with placebo (hazard ratio [HR], 0.70; 95% CI: 0.58-0.83; P < 0.001).
During follow-up, only those adverse events (AEs) considered to be treatment-related by the investigator were reported. The results reported from the entire ALSYMPCA safety population after the last patient’s final injection (radium-223, n = 600; placebo, n = 301) found that overall, 25 patients (4%) in the radium-223 arm and eight (3%) in the placebo arm had at least one treatment-related adverse effect.
In the radium-223 arm, grade 3 or higher AEs were anemia (five patients), aplastic anemia (one patient), leukopenia (two patients), neutropenia (two patients), and pathologic fracture (one patient). In the placebo arm, grade 3 or higher AEs were anemia (one patient), cardiopulmonary failure (one patient), nausea (one patient), and fatigue (one patient). There were three deaths: multi-organ failure and pneumonia (one patient each) in the radium-223 arm and cardiopulmonary failure (one patient) in the placebo arm. Other AEs in the radium-223 arm were thrombocytopenia, weight decrease, anorexia, musculoskeletal pain, and dizziness.
“Long-term safety data were assessed by specific diseases, including acute myelogenous leukemia, myelodysplastic syndrome, aplastic anemia, primary bone cancer, or primary cancer in other organs,” Dr. Nilsson reported. During follow-up, primary cancer in other organs was reported in five patients, two in the radium-223 arm and three in the placebo arm.
The 2014 Genitourinary Cancers Symposium is sponsored by the the American Society of Clinical Oncology (ASCO), the American Society for Radiation Oncology (ASTRO), and the Society of Urologic Oncology (SUO).