Biochemical disease-free rate and toxicity for men treated with iodine-125 prostate brachytherapy with d(90) ≥180 Gy.

Abstract

Iodine-125 ((125)I) prostate brachytherapy is planned with a prescribed dose of 145 Gy and minimal dose received by 90% of the prostate (D(90)) of 120-125% (174-181 Gy). We examined the clinical outcomes and toxicity profile of men receiving a D(90) (isodose enclosing 90% of the prostate) of ≥180 Gy. Between March 1999 and May 2006, 129 men (17% of our total brachytherapy population) treated with (125)I monotherapy for Stage T1-T2 prostate cancer received a D(90) ≥180 Gy. Implants were performed using transrectal ultrasonography and fluoroscopic guidance. The 1-month postplan dosimetry used magnetic resonance imaging-computed tomography fusion. The minimal follow-up was 2 years. Toxicity was scored according to the National Cancer Institute Common Terminology Criteria for Adverse Events toxicity scale, version 3. The median patient age was 63 years (range, 50-76), and the pretreatment prostate-specific antigen level was 5.5 ng/mL (range, 0.6-13.5). The Gleason score was ≤6 in 125 patients and was 7 in 4 patients. The median follow-up period was 40 months (range, 24-111), and the median D(90) was 186 Gy. The median minimal dose received by 30% of the urethra was 203 Gy, and the median rectal volume receiving a minimum of 100% of the prescribed dose was 0.81 cm(3). Acute Grade 2 genitourinary toxicity was seen in 5.4% and late Grade 2 in 7%. Late urinary retention (Grade 3) was seen in 2 patients (1.5%). Grade 1 rectal bleeding occurred in 9.3% and Grade 2 in 2.3%. On univariate logistic regression analysis, none of the clinical and dosimetric parameters predicted for rectal bleeding. Of 110 men who were potent before treatment, 81% remained potent 5 years after treatment. Three biochemical failures and only one local failure developed. The 5-year biochemical no evidence of disease rate using the "nadir plus 2" definition was 96.8%. A D(90) of ≥180 Gy is associated with excellent biochemical disease-free survival and acceptable toxicity.