Introduction: We investigated the value of the transitional zone index (TZI) for predicting treatment response to combination therapy involving α-blockers and 5α-reductase inhibitors for benign prostatic hyperplasia (BPH). Materials and Methods: Symptomatic BPH patients (n = 118) were randomized to receive 0.2 mg tamsulosin alone or with 0.5 mg dutasteride daily for 12 months. The TZI, International Prostate Symptom Scores, maximum urinary flow rates (Qmax), postvoid residual urine volumes, and prostate-specific antigen (PSA) were evaluated at baseline and after 12 months. The groups were subdivided according to a cut-off TZI value of 0.5 to compare treatment-related changes. Results: After 12 months, the combination therapy group had significantly greater decreases in prostate volume (p < 0.001), TZ volume (p < 0.001) and PSA (p < 0.001) than the monotherapy group, regardless of TZI. However, combination therapy resulted in significantly greater Qmax increases (p < 0.001) only in patients with a TZI ≥0.5. Multivariate analysis determined that TZI was the strongest independent predictor of the Qmax increase at 12 months in the combination therapy group (β = 13.7, p < 0.001). Conclusions: Greater Qmax improvement is expected with combination therapy comprising α-blockers and 5α-reductase inhibitors for patients with a TZI ≥0.5. The TZI may be useful for predicting the Qmax response to combination treatment for BPH.

Keywords:
α-1 adrenergic receptor antagonists, Transitional zone index , Prostatic hyperplasia, Combination therapy, 5α-reductase inhibitors
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© 2016 S. Karger AG, Basel
2016
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