Researchers have evaluated the use of Abiraterone acetate ( Zytiga ) ( 1,000 mg ) plus Prednisone ( 5 mg ) in patients with high risk, nonmetastatic, castration resistant prostate cancer.
Patients considered at high risk for progression to metastatic disease ( prostate specific antigen [ PSA ] 10 ng/ml or greater, or prostate specific antigen doubling time 10 months or less ) received Abiraterone acetate plus Prednisone daily in 28-day cycles.
The primary study end point was the proportion of patients in whom a 50% or greater prostate specific antigen reduction was achieved during cycles 1 to 6.
Secondary end points included time to prostate specific antigen progression, time to radiographic evidence of disease progression and safety.
Of the 131 enrolled patients 44 ( 34% ) remained on treatment with a median followup of 40.0 months.
Median age was 72 years ( range 48 to 90 ).
Of the patients 82.4% were white and 14.5% were black.
Median screening prostate specific antigen was 11.9 ng/dl and median prostate specific antigen doubling time was 3.4 months.
Prostate specific antigen was significantly reduced ( p less than 0.0001 ) with a 50% or greater prostate specific antigen reduction in 86.9% of cases and a 90% or greater reduction in 59.8%.
Median time to prostate specific antigen progression was 28.7 months ( 95% CI 21.2-38.2 ).
Median time to radiographic evidence of disease progression was not reached but on sensitivity analysis in 15 patients it was estimated to be 41.4 months ( 95% CI 27.6-not estimable ).
Baseline testosterone 12.5 ng/dl or greater and a 90% or greater prostate specific antigen reduction at cycle 3 were associated with longer time to prostate specific antigen progression and radiographic evidence of disease progression.
Outcomes in black patients were similar to those in other patients.
Adverse events, grade 3 or greater adverse events and serious adverse events were reported in 96.2%, 61.1% and 43.5% of patients, respectively.
In conclusion, in patients with high risk, nonmetastatic, castration resistant prostate cancer treatment with Abiraterone acetate plus Prednisone has demonstrated a significant 50% or greater prostate specific antigen reduction with encouraging results for the secondary end points, including the safety of 5 mg Prednisone. ( Xagena )
Ryan CJ et al, J Urol 2018; 200: 344-352