Radium-223 Dichloride Well-Tolerated in Pretreated Patients

New Orleans—Radium-223 dichloride (Ra-223) was well-tolerated with longer survival than seen previously in the phase 3 ALSYMPCA trial in a population of heavily pretreated patients in an expanded-access program. That was the primary finding of an analysis conducted recently by Neal Shore, MD, and colleagues. The researchers reported results of their analysis in a presentation at the AUA 2015 Annual Meeting.

The expanded-access program was designed to monitor acute and long-term safety of Ra-223. US patients with symptomatic bone-metastatic castration-resistant prostate cancer/hormone resistant prostate cancer were eligible. Inclusion criteria included ineligibility for or prior use of docetaxel. The treatment included Ra-223 50 kBq/kg administered intravenously every 4 weeks for six cycles with concomitant standard of care.

The program primary end points were Eastern Cooperative Oncology Group performance score, symptomatic skeletal events (SSEs), and treatment-emergent adverse events (AEs). Overall survival was among exploratory end points. The researchers conducted analyses to assess safety and overall survival for the entire cohort and for subgroups using concurrent enzalutamide or abiraterone.

Of the 184 patients treated, 65% (n=120) had prior use of abiraterone and 19% (n=35) had concurrent use of abiraterone; 32% (n=59) had prior use of enzalutamide and 14% (n=25) had concurrent use of enzalutamide. Overall, baseline characteristics were generally balanced (including the concurrent subgroups). The median age of study participants was 70 years, 92% were white, 59% (n=109) had prior docetaxel use, and 44% (n=81) received all six injections in the study protocol.

There were eight deaths among the study population during the treatment period; none of the eight deaths were related to Ra-223. Treatment-emergent AEs occurring in ≥10% of patients included anemia, fatigue, diarrhea, and nausea.

The rate of grade 3 to grade 5 treatment-emergent AEs was similar across concurrent and prior use subgroups: abiraterone concurrent use, 37%; prior use, 43%; enzalutamide concurrent use, 36%, prior use, 42% versus overall (41%). Median overall survival was 17 months.

“In heavily pretreated patients in this expanded-access program, Ra-223 was well-tolerated with a longer survival than previously seen in phase 3 ALSYMPA (15 months). Concurrently administered with either abiraterone or enzalutamide, RA-223 was well-tolerated, adding important information on concurrent use of Ra-223 and newer hormonal agents,” the authors said.

Source: Shore N, Vogelzang N, Fernandez D, et al. Radium-223 dichloride in Expanded-Access Setting in the United States: Overall and Concurrent Experience with Abiraterone or Enzalutamide. Abstract of presentation at the American Urological Association 2015 Annual Meeting, New Orleans, Louisiana, May 19, 2015