Background: Prostate cancer is a leading cause of cancer death in men. Treatment goals for men with advanced prostate cancer include prolonging survival, preventing or delaying symptoms due to disease progression, improving and maintaining quality of life, reducing treatment related morbidity. Androgen suppression therapy is considered a mainstay of treatment for men with advanced prostate cancer. However it is not clear whether early androgen suppression for men with locally advanced disease or asymptomatic metastases improves length and quality of life compared to androgen suppression deferred until signs and symptoms of clinical progression.
Objectives: This systematic review assessed the efficacy and adverse effects of primary therapy with early versus deferred androgen suppression therapy in men with advanced prostate cancer.
Search strategy: Randomized controlled trials were searched in general and specialized databases (MEDLINE, EMBASE, CancerLIT, Cochrane Library, VA Cochrane Prostate Disease register) and by reviewing bibliographies including those of the Blue Cross and Blue Shield Association Technology Evaluation Center/Evidence-based Practice Center of the Agency for Healthcare Research and Quality (BCBS/TEC-AHRQ) report No.4.
Selection criteria: All published randomized trials were eligible for inclusion provided they: randomized men with advanced prostate cancer to early versus deferred androgen suppression; reported overall, progression-free, and cancer-specific survival, and/or adverse events; did not utilize androgen suppression as adjuvant therapy to radiation treatment.
Data collection and analysis: An independent reviewer using a standardized form extracted information on trial characteristics, interventions, and outcomes. Results were reviewed for accuracy and discrepancies resolved by discussion. The main outcome measure for comparing effectiveness was the overall survival at 1, 2, 5 and 10 years. Progression-free survival, cancer-specific survival, complications due to disease progression and the incidence of adverse effects of treatment were also measured.
Main results: Four trials involving 2,167 patients were included in this review. All of the trials were conducted prior to use of prostate specific antigen (PSA) testing. There was variability between studies regarding the treatments used and the requirements for initiation of treatments. The percent overall survival at 1, 2, 5, and 10 years for the early treatment group was 88%, 73%, 44%, and 18%. For the deferred therapy group the percent overall survival was 86%, 71%, 37%, and 12%. The pooled estimate for the difference in overall survival favored early therapy but was significant only at 10 years when few patients had survived [OR = 1.16 (95% CI: 0.90 to 1.49) at 1 year, 1.08 (95% CI: 0.89 to 1.33) at 2 years, 1.19 (95% CI: 0.95 to 1.50) at 5 years, and 1.50 (95% CI: 1.04 to 2.16) at 10 years]. The pooled estimate of prostate cancer specific survival at 2, 5, and 10 years favored early therapy though the confidence intervals were wide and the results not statistically different. The risk differences at 2, 5, and 10 years were 2.7%, 5.8%, and 4.6%. Although each study used unique definitions of progression free survival, all studies found progression free survival was consistently better in the early intervention group at all time points. Complications due to disease progression were only reported in one study but were more frequent in the deferred treatment group. Adverse events due to treatment were also only reported in one study but occurred more frequently in the early treatment group.
Reviewer's conclusions: The evidence from randomized controlled trials is limited by the variability in study design, stage of cancer and subjects enrolled, interventions utilized, definitions and reporting of outcomes and the lack of PSA testing for diagnostic and monitoring purposes. However, the available information suggests that early androgen suppression for treatment of advanced prostate cancer reduces disease progression and complications due to progression. Early androgen suppression may provide a small but statistically significant improvement in overall survival at 10 years. There was no statistically significant difference in prostate cancer specific survival but a clinically important difference could not be excluded. These outcomes need to be evaluated with the evidence suggesting higher costs and more frequent treatment related adverse effects with early therapy. Additional studies are required to evaluate more definitively the efficacy and adverse effects of early versus delayed androgen suppression in men with prostate cancer. In particular trials should evaluate patients with advanced prostate cancer diagnosed by PSA testing and men with persistent or rising PSA levels following treatment options (e.g. radical prostatectomy, radiation therapy or observation) for clinically localized disease.