Enzalutamide confers small benefit vs. abiraterone in metastatic prostate cancer
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Key takeaways:
- Men treated with enzalutamide lived about a month longer than those who received abiraterone acetate.
- Men who received enzalutamide had longer time to next treatment switching and time to PSA response.
Enzalutamide conferred small but statistically significant improvements in outcomes vs. abiraterone acetate for men with metastatic castration-resistant prostate cancer, according to retrospective study results.
Men who received enzalutamide (Xtandi; Astellas Pharma) achieved modestly longer OS, time to next treatment switching or death, and time to PSA response.
Enzalutamide and abiraterone acetate are common treatments for men with metastatic castration-resistant prostate cancer. However evidence comparing the efficacy of the two agents is limited, according to study background.
Jennifer La, PhD, principal data scientist at U.S. Department of Veterans Affairs, and colleagues conducted a retrospective, multicenter cohort study to compare outcomes of 5,779 men (median age, 74.42 years; 61% non-Hispanic white) with metastatic castration-resistant prostate cancer treated with either abiraterone acetate or enzalutamide.
All men in the analysis began treatment in the U.S. Department of Veterans Affairs health care system between Jan. 1, 2014, and Oct. 30, 2022. Baseline characteristics appeared balanced between treatment groups.
Researchers evaluated restricted mean survival time (RMST) differences in OS, prostate cancer-specific survival, time to next treatment switching or death (TTS) and time to PSA response (TTR).
Median follow-up ranged from 38 to 60 months.
At 4 years, men who received enzalutamide on average exhibited a small but statistically significant improvement in OS (RMST = 24.29 months vs. 23.38 months; difference = 0.9 months; 95% CI, 0.02-1.79).
Additionally, men treated with enzalutamide achieved longer TTS (RMST improvement at 4 years = 1.95 months; 95% CI, 0.92-2.99), shorter TTR (RMST improvement at 4 years = 3.57 months; 95% CI, 1.76-5.38) and longer prostate cancer-specific survival (RMST improvement at 2 years = 0.48 months; 95% CI, 0.01-0.95).
Subgroup analysis showed enzalutamide extended OS among men who had not received prior docetaxel (RMST improvement = 1.14 months; 95% CI, 0.19-2.1) and those with PSA doubling time of 3 months or longer (RMST improvement = 2.23 months; 95% CI, 0.81-3.66).
Enzalutamide offered no significant benefit vs. abiraterone acetate for men who received prior docetaxel or those with PSA doubling time of less than 3 months.
Researchers acknowledged study limitations, including the inability to account for diagnostic Gleason score, tumor volume, location and number of metastases, duration of prior treatment and time since previous treatment. In addition, the comorbidity burden typically is higher among U.S. veterans, meaning results may differ among men with less comorbidity.
“The findings of this large-scale observational study with robust follow-up and rigorous methods may provide guidance for making well-informed decisions about [metastatic castration-resistant prostate cancer] treatment strategies,” La and colleagues wrote.
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La J, et al. JAMA Netw Open. 2024;doi:10.1001/jamanetworkopen.2024.28444.
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