Analyzing a continuous efficacy response in a long-term trial with high dropout rate

Abstract

Benign prostatic hyperplasia (BPH) is one of the most common medical conditions in older men in the United States. BPH is often associated with a reduction in quality of life and may progress to acute urinary retention (AUR), the inability to pass any urine. Recently, a 4-year placebo-controlled clinical trial known as the Proscar® Long-Term Efficacy and Safety Study (PLESS) demonstrated that finasteride use reduces the risk of developing AUR by 57% and the need for BPH-related surgery by 55%. The economic implications of these findings were investigated using a model-based decision-analytic approach to compare finasteride with both watchful waiting and α-blocker therapy. The modeling used the longest-term published controlled data concerning α-blockers, which were for the a-blocker terazosin. The base case considered a 64-year-old man (the mean age of a PLESS patient) with prostatic enlargement on digital rectal examination and moderate-to-severe symptoms of BPH. The model suggested savings in surgical and AUR costs with finasteride versus watchful waiting, with an estimated 25% of total finasteride costs recouped in savings on surgical events avoided in the first year. Over 2 years, the expected cost per patient starting finasteride therapy was $2304, whereas the expected cost per patient starting terazosin was $2334. Analyses also explored the variation in economic results by baseline levels of prostate-specific antigen (PSA), a proxy for prostate volume. For patients with PSA levels ≥1.4 ng/mL, expected 2-year costs with finasteride and terazosin were $2342 and $2479, respectively. For patients with PSA levels ≥3.3 ng/mL, expected 2-year costs with finasteride were $373 less than with terazosin ($2347 vs $2720). Results were robust over a range of model assumptions and cost estimates. The analyses illustrate that all medical interventions, including watchful waiting, have associated costs. Finasteride shows cost offsets compared with watchful waiting and cost savings compared with terazosin over 2 years. Finasteride appears to be more economical in men with higher PSA levels.