The 5α-reductase inhibitor (5-ARI), dutasteride, delays the clinical progression of prostate cancer (PCa) in patients with prostate-specific antigen (PSA) levels that have failed to reduce adequately following radical therapy for localized disease, report researchers.
"Elevated or rising PSA level after radical therapy is indicative of recurrent or residual PCa," say Fritz Schroder (Erasmus Medical Center, Rotterdam, the Netherlands) and colleagues. "Treatment options in men with biochemical progression after radical therapy are limited; therefore, a treatment with limited side effects that delays PSA progression and progression to clinical signs and symptoms could be a useful therapeutic option."
As reported in European Urology, 187 of 294 men with PSA failure (defined by the European Association of Urology guidelines) who were enrolled in the study completed the 24-month treatment period while 107 discontinued treatment prematurely, mainly due to disease progression.
At the end of the intention-to-treat study, those who were randomly allocated to receive dutasteride 0.5 mg had a significant 66.1% greater reduction in time to PSA doubling compared with those who received placebo once daily.
The between-group differences in time to PSA doubling became significant after 6 months and continued to increase through to month 24. The incidence of PSA doubling was 28% in the dutasteride group, compared with 57% in the placebo group over mean treatment periods of 456 days and 722 days, respectively.
Baseline PSA, baseline PSA doubling time, Gleason score, tumor stage at diagnosis, type of radical therapy received, hormone therapy use before screening, and time from radical therapy to screening, were significant predictors for time to PSA doubling.
However, the relative risk reduction in favor of dutasteride was similar with or without adjustment for these predictors, at 70% and 66%, respectively. This indicates that individuals in this setting may benefit from dutasteride treatment, regardless of baseline characteristics, say Schroder et al.
Dutasteride also significantly delayed disease progression compared with placebo, at a relative risk reduction of 59% in favor of dutasteride. Again the difference in treatment effects between the groups started to become significant after 6 months, and continued to increase through to month 24.
Furthermore, the incidence of adverse events (AEs), serious AEs, AEs leading to study discontinuation or withdrawal, and fatal AEs were similar between the groups and no fatal AE was considered to be related to study treatment.
"In the present study, dutasteride… resulted in reductions in both PSA-related progression events and also clinical-related outcomes," say Schroder et al.
"Nevertheless, additional data would be helpful in deciding if 5-ARIs could be considered a treatment option in this setting," remarks the team.
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