The results of an exploratory analysis published in the March 2000 issue of Urology suggest that prolonged combined androgen blockade (CAB) significantly increases survival in patients with advanced prostate cancer.
“A life is lost to prostate cancer every 13 minutes. The results from our analysis suggest that the duration of CAB therapy may be an important determinant of survival outcome, with longer being better,” said Michael F. Sarosdy, MD, South Texas Urology and Urologic Oncology, San Antonio, Texas. “Despite [the] clear value of CAB to block both adrenal and testicular androgen sources, long-term CAB has not been widely adopted as treatment for advanced prostate cancer. This finding has the potential to alter practice patterns, since the majority of physicians prescribe CAB for only the initial 2 weeks of hormonal therapy.”
Retrospective Analysis of Survival Data
The authors analyzed survival data from a previously published, controlled trial that evaluated the efficacy and tolerability of two antiandrogens, bicalutamide(Drug information on bicalutamide) (Casodex) and flutamide(Drug information on flutamide) (Eulexin), each combined with a monthly depot preparation of goserelin(Drug information on goserelin) (Zoladex) or leuprolide (Lupron), in 813 patients with metastatic prostate cancer. The primary objective of this retrospective analysis was to explore whether patients who received a short course of antiandrogens as part of CAB therapy (< 120 days) would have a different survival outcome than those who received prolonged CAB treatment (³ 120 days). The 120-day point was chosen to distinguish between short- and long-term CAB use because, according to prescription data, this is the average duration of antiandrogen use in the United States.
The analysis demonstrated a statistically significant survival benefit in favor of patients receiving prolonged CAB therapy, with a hazard ratio of 0.275 (95% confidence interval, 0.213 to 0.355; P = .0001). The median survival of patients who received ³ 120 days of CAB therapy was 1,035 days, as compared with 302 days for patients who received < 120 days of CAB.
Second Analysis of Patient Subset Confirms Survival Benefit
To address the potential bias associated with early deaths resulting in a short duration of therapy, a survival analysis was also performed in the subset of patients (N = 544) who lived at least 2 years beyond the date of randomization. The median survival time of patients who received ³ 120 days of CAB therapy was 1,433 days, as compared with 1,061 days for patients who received < 120 days of CAB therapy. The hazard ratio was 0.415 (95% confidence interval, 0.246 to 0.702; P = .001). This second analysis confirmed the results of the first analysis.
“This is the first analysis ever to investigate the duration of CAB in a trial in which all patients received CAB. All others have compared CAB to no CAB,” said Dr. Sarosdy.
Adverse Events
In clinical trials, the most commonly reported adverse events in patients given bicalutamide (50 mg) plus a luteinizing hormone–releasing hormone analog were hot flashes, pain, back pain, asthenia, constipation, pelvic pain, infection, nausea, dyspnea, peripheral edema, diarrhea, hematuria, and nocturia. Periodic liver function tests should be considered for patients receiving long-term therapy.
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