Concomitant use of enzalutamide and radium-223 as third-line therapy for patients with bone-dominant metastatic castration-resistant prostate cancer (mCRPC) does not improve survival compared with the use of radium-223 alone, according to a recent study.
Mohamed E. Ahmed, MB, BCh, of Mayo Clinic in Rochester, Minnesota, and colleagues studied 51 patients with bone-dominant mCRPC treated with radium-223, an alpha-particle-emitting radiopharmaceutical that selectively targets bone metastases. Of these patients, 32 received radium-223 alone (group A) and 19 received radium-223 concomitantly with the second-generation antiandrogen drug enzalutamide (group B). All patients presented with advanced mCRPC, with 100% of patients having had prior second-generation hormone therapy and 95% of patients also having had prior chemotherapy.
Median overall survival (OS) times were 20.4 months in group A and 17.5 months in group B, a difference that was not statistically significant, Dr Ahmed’s team reported online in Clinical Genitourinary Cancer.
The only independent risk factors associated with improved OS, in both univariate and multivariate analyses, were a baseline PSA level of less than 30 ng/mL and an ECOG performance status of less than 2. The investigators observed a nearly 4-fold increase in OS as a result of these 2 factors. Median OS was approximately 12.7 months for patients with a baseline PSA of 30 ng/mL or higher compared with 25.3 months among those with a baseline PSA of less than 30 ng/mL. On multivariable analysis, a baseline PSA level less than 30 ng/mL was significantly associated with an 83% decreased risk for death compared with a level of 30 ng/mL or more.
Median OS was approximately 21.5 months for patients with an ECOG performance status of less than 2 compared with 11.9 months for those with an ECOG performance status of 2 or higher. An ECOG performance status of less than 2 was significantly associated with a 75% decreased risk for death compared with an ECOG performance status of 2 or higher.
Dr Ahmed and colleagues said their study suggests criteria that might help clinicians select patients with advanced prostate cancer for radium-223 treatment.
Study limitations include its retrospective design and relatively small sample size.
Ahmed ME, Joshi VB, Badawy M, et al. Radium-223 in the third-line setting in metastatic castrate-resistant prostate cancer (mCRPC): impact of concomitant use of enzalutamide on overall survival and predictors of improved overall survival. Published online January 6, 2021. Clin Genitourin Cancer. doi:10.1016/j.clgc.2020.12.009