Abiraterone plus prednisolone, enzalutamide a toss-up in castration-resistant prostate cancer

The combination of abiraterone plus prednisolone appears to have similar efficacy and safety as enzalutamide in the treatment of patients with nonmetastatic castration-resistant prostate cancer (CRPC), according to a study.

Data from the subgroup of 41 patients with nonmetastatic CRPC in the ENABLE cohort showed no significant differences in prostate-specific antigen (PSA) response rate (≥50-percent decrease from baseline) in the enzalutamide and abiraterone–prednisolone arms (80 percent and 64 percent, respectively) as well as in the primary endpoint of time to PSA progression (median, 33.45 vs 27.37 months, respectively; p=0.2169). [ESMO Asia 2023, abstract 263MO]

Furthermore, all survival outcomes were comparable between the two treatment arms, reported lead study author Dr Kouji Izumi of the Department of Integrative Cancer Therapy and Urology at Kanazawa University Graduate School of Medical Science in Kanazawa, Japan.

The median overall survival was not reached with enzalutamide and 33.7 months with abiraterone–prednisolone (hazard ratio, 1.47, 95 percent confidence interval [CI], 0.47–4.62; p=0.53). The respective radiographic progression-free survival rates were 23.10 months and 16.10 months (p=0.61), while the disease-free survival rates were 24.67 months and 27.66 months (p=0.87).

Likewise, safety did not significantly differ between the two treatment arms. The most common adverse events (AEs) among enzalutamide-treated patients were any-grade anaemia (20 percent), malaise (27 percent), decreased appetite (20 percent), and nausea (13 percent). Among patients treated with abiraterone–prednisolone, on the other hand, the most common AEs were any-grade anaemia (15 percent), malaise (8 percent), fatigue (8 percent), and body weight loss (8 percent).

Izumi noted a very low incidence of grade 3 or higher AEs, with only four and six cases recorded in the enzalutamide and abiraterone–prednisolone arms, respectively.

In terms of systemic therapies used after the study treatments, 20 percent of patients in the enzalutamide arm and 23 percent of those in the abiraterone–prednisolone arm received docetaxel. Moreover, 13 percent and 27 percent of patients in the respective groups were given the alternative study treatment.

Taken together, these data suggest that abiraterone–prednisolone is expected to show a similar efficacy and safety profile as enzalutamide, with neither agent being better than the other for treating nonmetastatic CPRP patients, as Izumi pointed out.

The ENABLE subanalysis included 15 patients in the enzalutamide arm (median age 78.3 years) and 26 in the abiraterone–prednisolone arm (median age 77.4 years). Most of the patients were fully active, with no restrictions on activities (Performance Status 0; 73 percent in both arms) but had a Gleason score of 9 (40 percent and 46 percent, respectively). The median PSA level at diagnosis was 49.9 ng/mL in the enzalutamide arm and 53.8 ng/mL in the abiraterone–prednisolone arm.