Patterns of local failure following prostate brachytherapy.

PURPOSE: We describe biopsy results in patients with prostate cancer treated with brachytherapy.
MATERIALS AND METHODS: A total of 1,562 men with localized prostate cancer were treated with permanent prostate brachytherapy, of whom 508 agreed to ultrasound guided biopsies 2 years after the completion of all therapy. Median followup was 6.7 years (range 2 to 14.6) and median prostate specific antigen was 7.4 ng/ml (range 0.3 to 300). Disease was categorized as Gleason score less than 7 in 74.8% of patients, stage T2a or less in 64.2%, low risk in 43.1%, intermediate risk in 24.2% and high risk in 32.7%. Of the 508 men 315 (62%) received (125)I, 110 (21.7%) received (103)Pd and 83 (16.3%) received (103)Pd and external beam radiotherapy. A total of 237 men (46.7%) received a short course of hormonal therapy (3 to 9 months). Subsequent biopsies were performed after 2 years if initial biopsy was positive or prostate specific antigen increased. Post-implantation dosimetry results were grouped into low, normal and high dose. Associations were tested by chi-square analysis. Survival functions were calculated with Kaplan-Meier analysis and Cox regression.
RESULTS: A total of 643 biopsies were performed in 508 men between 2 and 11 years after implantation. Of the 508 men 39 (7.7%) had a final positive biopsy. Positive biopsy was associated with high prostate specific antigen (p=0.035), stage (p=0.003), risk (p=0.024), no hormonal therapy (p=0.002) and low dose (p<0.0001). On multivariate analysis only dose and hormonal therapy were significant (p<0.0001 and p=0.004, respectively). Of the patients 80% were free of PSA failure at 10 years if final biopsy was negative compared to 27.3% with a positive biopsy (p<0.0001). Death from prostate cancer was associated with a positive biopsy (OR 18.5, 95% CI 2.3-143, p<0.0001). Of the 52 men with a positive biopsy at year 2, 23 (44.2%) had negative results on subsequent biopsy, while 10 of the 456 (2.2%) with negative 2-year biopsies showed positive results. Positive biopsy occurred in the prostate only in 31 of 39 men (79.5%), in the prostate and seminal vesicles in 3 (7.7%), and in the seminal vesicles only in 5 (12.8%).
CONCLUSIONS: Patients undergoing prostate brachytherapy must receive an adequate radiation dose to eradicate local disease. Hormonal therapy may benefit local control in patients with intermediate to high risk disease. Extraprostatic biopsies should be performed in patients with local failure who are considering salvage therapy to rule out seminal vesicle involvement.