Clinical investigation: prostate
Factors influencing risk of acute urinary retention after TRUS-guided permanent prostate seed implantation

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Abstract

Purpose: To look for factors predictive of acute urinary retention (AUR) after permanent seed prostate brachytherapy.

Methods and Materials: From March 1999 to February 2001, 150 permanent seed prostate implants were performed at Princess Margaret Hospital (Stage T1c, n = 113; T2a, n = 37; mean prostate-specific antigen level 5.9 ng/mL, prescription dose 145 Gy per Task Group No. 43). α-Blockers were used routinely after implantation. Dosimetry was based on the 1-month postimplant CT scan. The International Prostate Symptom Score (IPSS) and catheterization were recorded at 1 month and 3 months and then every 3 months. The following variables were examined: age, baseline IPSS, prior androgen ablation, prostate transrectal ultrasound volume, number of seeds, D90, V100, V200, and urethral dose.

Results: Twenty patients (13%) experienced AUR. No difference was seen in the mean D90 (149 Gy vs. 152 Gy, p = 0.6), V100 (90% vs. 91%, p = 0.6), V200 (23% vs. 25% p = 0.4), IPSS (6.4 vs. 5.9, p = 0.8), or maximal urethral dose (204 Gy vs. 210 Gy, p = 0.5). The prostate volume was significantly larger in men with AUR (39.8 cm3 vs. 34.3 cm3, p = 0.003), and the mean number of seeds was higher (112 vs. 103, p = 0.006). Of the 20 patients experiencing AUR, 11 (55%) had received prior antiandrogen therapy to downsize their prostates vs. 35 (27%) of the 130 who did not have AUR (p = 0.02). Multivariate analysis showed prostate volume and prior hormone use to be independent predictors of AUR.

Conclusions: Implant quality as determined by D90, V100, V200, and urethral dose did not predict AUR. Prostate size was the major determinant of AUR. For any given prostate size, prior androgen ablation increased the risk of AUR. Men with larger prostates should be aware of the increased risk when contemplating brachytherapy.

Introduction

Permanent seed prostate brachytherapy is becoming an increasingly popular option in the management of clinically localized prostate cancer. It is estimated that in 2001, >50% of American Medicare patients with newly diagnosed localized prostate cancer will have been treated with brachytherapy. By 2005, 50% of all appropriate newly diagnosed cases will receive brachytherapy (1). This option is often perceived as having a better side effect profile than radical prostatectomy. Nonetheless, a significant proportion of men will experience prolonged urinary dysfunction. Acute urinary retention (AUR) rates generally range from 5% to 15% and may result in a prolonged period of catheterization, intermittent self-catheterization, a suprapubic tube, or even a transurethral resection, if persistent. This can have a major impact on quality of life for the individual. The ability to predict more severe urinary toxicity would be beneficial in counseling patients who are trying to make a treatment choice.

We report the experience at the Princess Margaret Hospital/University Health Network with 150 permanent seed implants.

Section snippets

Methods and materials

Permanent radioactive seed implantation as management for early-stage localized prostate cancer was approved and funded by the Ministry of Health in the Province of Ontario in February 1999. Provincial evidence-based guidelines (2) developed by the Cancercare Ontario Provincial Guidelines Group (genitourinary division) restrict the availability to appropriately selected patients (Stage T1c/T2a, Gleason score ≤6, prostate-specific antigen [PSA] level <10 ng/mL). From March 1999 to February 2001,

Results

The median follow-up was 13 months (range 3–27). The rate of urinary retention requiring catheterization after implantation was 13% (20 of 150). The time of onset was variable, but most occurred soon after implantation, 6 within the first 24 h, 9 between Days 2 and 7, and 2 in the second week. The remaining 3 were late onset at 2, 5, and 5 months. Two of these men continued intermittent self-catheterization for 18 months. The third was catheterized for severe urinary symptoms, but was not in

Discussion

The popularity of prostate brachytherapy is partially attributable to a perceived favorable toxicity profile. Some degree of urinary morbidity related to urethritis and prostatitis is common in the postimplant period. Symptoms tend to peak at about 2 months (10), with maximal IPSS at 1 month (11), but improve with time, as do function and bother scores (12). Severe long-term urinary morbidity is reported in 3–12%. Health-related quality of life returns to near baseline by 3 months (13), and

Conclusions

AUR is the most common adverse event after permanent seed, low-dose-rate prostate brachytherapy. Prior knowledge of an individual’s relative risk of AUR would be useful in counseling patients before the procedure. In this series of 150 consecutive implants, prostate volume and the use of prior hormonal therapy to downsize the prostate were independent predictors of AUR. The systematic use of the IPSS questionnaire to screen patients and to direct those with significant lower urinary tract

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