4CPS-128 Effectiveness of abiraterone acetate and enzalutamide in metastatic castration-resistant prostate cancer

BackgroundAbiraterone acetate (AA) and enzalutamide are authorised oral therapies in the treatment of metastatic castration-resistant prostate cancer (mCRPC), which act by inhibiting androgen synthesis.PurposeTo compare the effectiveness of AA and enzalutamide in patients with mCRPC.Material and methodsRetrospective observational study between January 2015 and July 2017 in patients who had been treated with AA and enzalutamide for at least 1 month.Patients’ medical records were reviewed and the following data were collected: sex, age, Eastern Cooperative Oncology Group (ECOG) scale, degree of tumour aggressiveness (GLEASON scale) and pretreatment with docetaxel. The clinical variables were reduction in prostate-specific antigen (PSA) during the first trimester of treatment (≥50% and≥90%) and progression-free survival (PFS), defined as the duration of pharmacological treatment until suspension by progression of the illness.The statistical tests used, through the IBM SPSS®Statistics 23 program, were: student’s t-test to assess the SLP and the Chi-square and Fisher’s exact test to assess the PSA response.ResultsTwenty-six patients with AA and 22 with enzalutamide were treated. The median age for AA was 76 (58–92) vs 75.5 years (56–91) enzalutamide. ECOG ≤1 was found in 80.8% AA vs 90.9% enzalutamide. The GLEASON value ≥8 at the beginning of the treatment was 53.8% AA vs 77.3% enzalutamide. A 65.4% AA had not received pretreatment with docetaxel vs 72.7% enzalutamide. During the study period, 46.2% of patients treated with AA discontinued treatment, with an SLP in 228 days (45–528) vs 50% in the enzalutamide group with an SLP of 216 (83–446), with no statistically significant differences in both groups (p=0.848). The reduction of PSA was ≥50% in 53.85% AA vs 58.85% enzalutamide, with no statistically significant differences (p=0.579). The reduction in PSA ≥90% occurred in 19.23% AA vs 18.18% enzalutamide, with no statistically significant difference (p=1.).ConclusionAccording to the analysed data we can conclude that abiraterone acetate and enzalutamide have the same effectiveness measured as PFS and PSA reduction. Even so, it is necessary to take into account the low number of patients treated, so more studies are necessary to confirm this comparison.No conflict of interest