The Influence of Baseline Parameters on Changes in International Prostate Symptom Score with Dutasteride, Tamsulosin, and Combination Therapy among Men with Symptomatic Benign Prostatic Hyperplasia and an Enlarged Prostate: 2-Year Data from the CombAT Study

Background: Knowledge of baseline factors that influence outcomes for men with benign prostatic hyperplasia (BPH) receiving medical therapy may help to improve outcomes and cost effectiveness. Objectives: To examine the influence of baseline parameters on changes in International Prostate Symptom Score (IPSS) and maximum urinary flow rate (Q_max) in men with BPH receiving dutasteride, tamsulosin, or a combination of the two using 2-yr Combination of Avodart and Tamsulosin (CombAT) study data. Design, setting, and participants: CombAT is an ongoing, 4-yr, multicentre, randomised, double-blind study in 4844 men aged ≥50 yr with clinical diagnosis of BPH, IPSS ≥12, prostate volume ≥30 cm³, prostate-specific antigen (PSA) 1.5-10 ng/ml, and Q_max >5 and ≤15 ml/s with minimum voided volume ≥125 ml. Intervention: Daily tamsulosin 0.4 mg, dutasteride 0.5 mg, or the combination. Measurements: Post hoc analyses of mean IPSS and Q_max changes from baseline by treatment group and by baseline prostate volume, PSA, age, body mass index (BMI), IPSS, IPSS quality of life (QoL) score, BPH Impact Index score, Q_max, and previous BPH medical therapy. Results and limitations: Combination therapy was more effective than either monotherapy after 24 mo in improving IPSS in all baseline subgroups, with benefit onset varying by baseline prostate volume. Combination therapy was also more effective in improving Q_max versus tamsulosin in all subgroups and versus dutasteride in 10 of 18 subgroups. At 24 mo, dutasteride monotherapy resulted in significantly greater IPSS improvements versus tamsulosin in men with lower age, worse symptoms, worse QoL, less bother, higher BMI, greater Q_max, higher prostate volume, and higher PSA at baseline. Post hoc analyses, the lack of placebo control, and the exclusion of men with unsuccessful medical BPH treatment are study limitations. Conclusions: Combination therapy with tamsulosin and dutasteride affords the greatest and the most rapid symptomatic benefit among men with higher baseline prostate volume and is effective regardless of previous BPH medical therapy. Dutasteride monotherapy is more effective than tamsulosin in men with higher baseline prostate volume or PSA and worse symptoms.