Variations of transition zone volume and transition zone index after transurethral needle ablation for symptomatic benign prostatic hyperplasia

Abstract

Transurethral needle ablation (TUNA) is less invasive than other therapies for benign prostatic hyperplasia (BPH) and produces coagulative necrosis within selected adenoma lesions. The action mechanism of TUNA is still obscure, even though many early studies have demonstrated good clinical results of TUNA. It is of interest and importance to know how TUNA influences the volume of the intraprostatic region responsible for bladder outlet obstruction in order to elucidate the anatomical action mechanism of TUNA. We retrospectively investigated postoperative variations in volumetric parameters of whole prostate volume (PV), transition zone volume (TZV) and transition zone index (TZI = TZV/PV) in 41 patients with symptomatic BPH who were treated with TUNA. The data were analyzed statistically in relation to the preoperative overall severity and postoperative therapeutic efficacy. Both PV and TZV showed a significant decrease at 3 months after TUNA (P < 0.01) as did the symptom score, quality of life (QOL) score and functional variables, and a decreased level of PV and TZV was sustained until 12 months of follow-up when compared to the baseline (P < 0.01 at 6 months, not significant at 12 months). TZI also showed a similar pattern with a significantly decreased level until the postoperative 6th month (P < 0.05 at 6 months, not significant at 12 months). In 'moderate' cases, TZI achieved the minimum value (0.44 +/- 0.13, P < 0.05 compared to the baseline) at 3 months of follow-up, but the level immediately increased, while in 'severe' cases, TZI gradually decreased and achieved the minimum value (0.44 +/- 0.08, P < 0.05 compared to the baseline) at 12 months of follow-up. In the evaluation by postoperative therapeutic efficacy, there were no significant differences in PV, TZV and TZI between 'excellent and good' cases (E/G group) and 'fair and poor/worse' cases (F/P group) at the baseline or 3 months of follow-up. Both of the efficacy groups showed a significant decrease in PV, TZV and TZI at 3 months when compared to the baseline (P < 0.05). The mean decrease in TZI was significantly larger in the E/G group than in the F/P group (0.064 +/- 0.13 vs 0.027 +/- 0.12, P < 0.05). Therapeutic efficacy of TUNA did not depend on the baseline value of PV, TZV and TZI, but on variation of a decrease in TZI during follow-up. Moreover, a slow and lasting decrease in TZI seemed to influence durability of the therapeutic efficacy of TUNA, which was clearly observed in 'severe' cases with a larger prostatic volume than in 'moderate' cases.