Radium-223 is a first-in-class radiopharmaceutical for prostate cancer and affects areas of increased bone turnover such as metastases. The phase III ALSYMPCA trial was a double-blind, randomized, placebo-controlled trial evaluating the safety and efficacy of radium-223 in patients with symptomatic bone metastases from castrastion-resistant prostate cancer.

The primary efficacy endpoint was overall survival (OS), Finkelstein says, and the key secondary efficacy endpoint was time to first symptomatic skeletal event. In the trial, all patients continued androgen deprivation therapy and received best standard of care (local external beam radiation therapy, corticosteroids, antiestrogens, estrogens, or ketoconazole). Therapy was continued until unacceptable toxicity or initiation of cytotoxic chemotherapy, other systemic radioisotopes, hemibody external beam radiation therapy, or other investigational drugs.

In the trial, the median age of patients was 71 years old, with a range from 44 to 94. The racial distribution was 94% Caucasian, 4% Asian, 2% black, and less than 1% other. The ECOG performance status for patients was 0 to 1 in greater than 86% of patients. Additionally 85% of patients had 6 or more bone scan lesions. Opiod pain medications used for cancer-related pain were used by 54% of patients, while 44% used non-opiod pain medications, and 2% used node pain medication.

The pre-specified interim analysis of OS revealed a statistically significant improvement in patients receiving radium-223 plus best standard of care versus placebo plus best standard of care. The follow-up was consistent with the interim analysis.