Permanent Seed Brachytherapy for Low Risk Prostate Cancer, Long Term Outcome, and Urinary Toxicity

Abstract

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. 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. 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 [Inter-quartile 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. 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.