Permanent seed brachytherapy for low risk prostate cancer, long term outcome, and urinary toxicity.

Abstract

66 Background: Low dose rate seed brachytherapy is an established treatment modality for low risk prostate cancer (CaP). Herein, we report long term biochemical control and urinary toxicity from a single institution. Methods: Data from a prospectively-collected institutional database was used, completed with retrospective chart reviews. All patients with low-risk CaP (NCCN criteria) who underwent ultrasound-guided permanent iodine-125 brachytherapy from March 1999 to December 2005 were included. Urinary function was evaluated by the International Prostate Symptom Score (IPSS). PSA relapse was defined by Phoenix Criteria (nadir + 2 ng/ml). Time to IPSS return-to-baseline score ±3 was recorded. Results: 582 patients with a median age of 64 years were included. Median initial PSA was 5.5 ng/ml (0.3-10). 66% and 34% were T1 and T2a, respectively. Gleason score was 6 (96%) and < 6 (4%). Prescription dose was 145Gy, with a median V100 coverage of 94% (IQR [interquartile range] 89-97%) and median D90 of 157Gy (IQR 144-171 Gy). With a median follow up of 131 months (IQR 94-149 months), 27 patients showed biochemical failure (4.6%), and PSA bounce was detected in 38 cases (7%). Biochemical progression-free rates were 97% (96-98%), 96% (94-97%), and 94% (91-96%) at 5, 10, and 15 years, respectively. Median PSA level at 5, 10 and 15 years was 0.06, 0.05 and 0.018 ng/ml, respectively. PSA relapses were observed out to 148 months. At 1, 5, 10 and 15 years, 5.5%, 16.5%, 39.5% and 89.2% of patients were lost to PSA follow up. Median baseline IPSS score was 5. In 515 (88.5%) patients IPSS returned to baseline, with a median time to return-to-baseline of 9 months. The proportion of return-to-baseline at 1, 2, 5, and 10 years was 62%, 75%, 88%, and 90%, respectively. 22 (4%) patients required post-implant urinary catheter. After 3, 6 and 12 months, 9 (1.5%), 6 (1%) and 4 (0.7%) patients continued to be catheterized. Conclusions: Within the limits of retrospective analysis, permanent seed brachytherapy for low risk prostate cancer is an effective treatment modality with low urinary toxicity. Treatment resulted in excellent long-term biochemical control although late relapses were observed.