Factors predicting for urinary incontinence after prostate brachytherapy

Purpose: To define risk factors that predict for urinary incontinence after I-125 prostate brachytherapy. Methods and Materials: Urinary incontinence after I-125 prostate brachytherapy was evaluated using a patient self-assessment questionnaire based on the NCI Common Toxicity Criteria (version 2). Grade 0 is defined as no incontinence; Grade 1 incontinence occurs with coughing, sneezing, or laughing; Grade 2 is spontaneous incontinence with some control; and Grade 3 is no control. One hundred fifty-three patients received monotherapy (145 Gy) I-125 implants between October 1996 and December 2001, and 112 (75%) responded to our survey. Median follow-up was 47 months (range, 14-74 months). Patient characteristics included a preimplant prostate-specific antigen less than or equal to10, Gleason score less than or equal to6, and stage less than or equal toT2b. CT-based postimplant dosimetry was analyzed approximately 30 days after the procedure, and dose-volume histograms of the prostate and the prostatic urethra were generated based on contoured volumes. Dosimetric parameters evaluated as predictive factors for incontinence included the prostate volume; total activity implanted; number of needles; number of seeds; seed activity; urethral D-5, D-10, D-25, D-50, D-75, and D-90 doses; prostate D-90 doses; and prostate V-100, V-200, and V-300. Clinical parameters evaluated included age, Gleason score, prostate-specific antigen, preimplant International Prostate Symptom Score (I-PSS), and length of follow-up. Results: Urethral D, dose and preimplant I-PSS predicted for urinary incontinence on multivariate analysis (P = 0.002 and p = 0.003, respectively). Twenty-eight patients reported Grade I incontinence (26%), and 5 patients reported Grade 2 (5%). Patients with Grade I and 2 incontinence were analyzed together, because of the small number of patients who experienced Grade 2. No patients reported Grade 3 incontinence. Mean urethral D-10 was 314 +/- 78 Gy in patients with Grade 0 compared with 394 +/- 147 Gy in patients with Grades 1, 2 incontinence (p = 0.002). The incidence of incontinence doubled as the urethral D-10 dose increased above 450 Gy. Patients with Grade 0 had a mean preimplant I-PSS score of 6.6 +/- 4.5 compared with 10.0 +/- 6.4 for Grades 1, 2 (p = 0.003). A significant increase in the incidence of incontinence was noted when the preimplant I-PSS was greater than 15. No relationship was noted between incontinence and prostate volume, total activity implanted, or the number of needles used (p = 0.83, p = 0.89, p = 0.36, respectively). Conclusion: Urethral D-10 dose and preimplant I-PSS are predictive for patients at higher risk of urinary incontinence. To decrease the risk of this complication, an effort should be made to keep the urethral D-10 dose as close to the prescribed dose as possible, and the preimplant I-PSS should be thoroughly evaluated in an attempt to select patients with scores less than 15. (C) 2004 Elsevier Inc.