Late Urinary Retention When Using High Dose Rate Prostate Brachytherapy As A Boost In Local And Locally Advanced Prostate Cancer

Late urinary retention (UR) due urethral stricture requiring catheterization or invasive procedures is a known complication that may occur when using high dose rate brachytherapy (HDR-B) to boost external beam radiation therapy (EBRT), however, the factors associating dosimetric, treatment and clinical factors with this complication are not well known. We evaluated the incidence of UR when using HDR-B to boost EBRT. From March 1997 to March 2000 a total of 108 patients with biopsy proven prostate adenocarcinoma, treated with pelvic localized EBRT in combination with HDR-B as boost. Patients with any of the following characteristics were eligible: Gleason scored (GS), initial PSA level dosage, clinical stage (CS) T3a or lesser and, prostate volume up to 60cc. Patients were treated with conventional 45 Gy, through a 6 MV photons Varian Linear Accelerator, in 4 fields (box technique) and boosted with HDR-B, via the micro-Selectron-HDR Ir-192, remote after loading system, with 16 to 20 Gy given in 4 BID fractions. Median age and f-up of patients was 68 years and 44 months. Characteristics of patients are in table 1(table 1). Median prostate volume was 35 cc. Crude 5-year UR free survival was 95.4% and 5-year actuarial UR free survival was 86.2%. Univariate analysis showed that the predictive factors for UR were age above 65 years old (p = 0.0416) and active length of needles more than 3.5 cm (p = 0.0158). CS (p = 0.0692), iPSA (p = 0.4323), GS (p = 0.1623), urethral BED above 115 Gy3 (p = 0.395), previous TURP (p = 0.1101), prostatic vol >35 cc (p = 0.0465), use of NAAD (p = 0.2757), n. of needles per implant (p = 0.7277), previous symptoms (p = 0.2957) were not predictive factor for UR. On multivariate analysis by Cox regression age was the only predictive factor (p = 0.027), Figure 1. HDR-B appear to offer a safe, reproducible, and effective method of boosting conventional EBRT in patients with locally advanced prostate cancer. Late toxicity with this technology reveal rates paralleling those achieved with other forms of treatment such low dose permanent implants and radical prostatectomy. View Large Image Figure ViewerDownload (PPT)