Urodynamic changes at 18 months post-therapy in patients treated with external beam radiotherapy for prostate carcinoma.

PURPOSE: To quantify the effect of radiotherapy (RT) on urodynamics at 18 months post-therapy, using urodynamic study, in prostate cancer patients undergoing definitive external beam RT. METHODS AND MATERIALS: A total of 17 patients with clinically localized prostate cancer were accrued into a single-arm prospective study. Fifteen of 17 patients completed scheduled multichannel video-urodynamic study at baseline as well as 3 and 18 months after RT. Baseline quantitative urodynamic parameters were compared with those at 18 months post-RT to assess the nature and extent of urodynamic change brought about by RT. These quantitative changes were further correlated to the change in self-assessed qualitative urinary function measured by International Prostate Symptom Score (IPSS), Quality of Life assessment index (QoL), and urinary functional inquiry.
RESULTS: The statistically significant quantitative changes detected by the urodynamic study at 18 months post-RT were decrease in bladder capacity and bladder volume at first sensation in both the supine and upright position, and reduction in bladder volume at desire to void in the supine position. In our cohort, the mean reduction in bladder capacity was 100 mL in the supine position and 54 mL in the upright position. No statistically significant change was observed with regard to pressure, maximum flow rate, voided volume, or postvoid residual volume. Furthermore, there was no statistically significant change in bladder compliance, bladder instability, or bladder outlet obstruction. No statistically significant change in self-assessed qualitative urological function was observed between baseline and 18 months post-RT, measured by the 3 parameters (IPSS, QoL, and urinary frequency over 24 h).
CONCLUSIONS: This is the first quantitative study that prospectively evaluated the effect of RT on urodynamics in prostate cancer patients receiving definitive RT. The statistically significant changes at 18 months post-RT were reduction in bladder capacity, reduction in bladder volume at first sensation, and decrease in bladder volume at desire to void. Despite the decrease in these parameters, there was no statistically significant adverse effect of RT on bladder compliance, bladder stability, or bladder outlet flow. This observation corresponded well with no significant change in IPSS, QoL, or urinary frequency over 24 h. Furthermore, these results confirm the notion that most prostate cancer patients generally tolerate RT very well.