Relationship between the transition zone index of the prostate gland and urinary morbidity after brachytherapy

To evaluate whether urinary symptomatology after prostate brachytherapy is related to the preimplant transition zone index (TZI = transition zone volume/prostate gland volume).

A total of 170 consecutive patients without a prior history of transurethral resection of the prostate gland (TURP) underwent transperineal ultrasound-guided prostate brachytherapy for clinical T1c-T3a carcinoma of the prostate gland. Prostate gland and transition zone dimensions and volumes were measured by prolate ellipsoid calculation from the static ultrasound images. The relationship between TZI and various measures of urinary dysfunction including normalization of International Prostate Symptom Scores (IPSS), catheter dependency, the need for a subsequent TURP, and the duration of alpha-blocker dependency were evaluated. Additional clinical parameters evaluated included the relationship between TZI and patient age, clinical T stage, prostate ultrasound volume, neoadjuvant hormonal manipulation, and preimplant IPSS. For all indices of urinary dysfunction other than serial IPSS, the median patient follow-up was 89.3 weeks. The median follow-up for serial IPSS evaluations was 37.3 weeks with a mean of 11.2 questionnaires per patient.

The mean TZI for the 170 patients was 0.23 +/- 0.06 (prostate gland volume 30.3 +/- 8.7 cm(3), transition zone volume 7.3 +/- 3.6 cm(3)). The TZI correlated with the time for IPSS normalization, the maximum IPSS after brachytherapy, and the maximum increase in IPSS. Conversely, the TZI did not correlate with either catheter dependency or alpha-blocker dependency. Two of 170 patients (1.2%) required a postimplant TURP. The TZI in these 2 patients (0.34) was statistically different (P = 0.016) from the mean.

In prostate brachytherapy patients, the preimplant TZI predicted the need for a subsequent transurethral resection. The TZI also correlated with multiple variants of IPSS. Conversely, TZI did not correlate with either catheter dependency or alpha-blocker dependency.