Long-term Outcomes for Clinically Localized Prostate Cancer Treated With Permanent Prostate Brachytherapy With Pd-103

Abstract

In view of the prolonged natural history of prostate cancer, long-term follow-up is warranted to determine the efficacy of treatment. We evaluated the outcome of our prostate brachytherapy patients that were treated at least 15 years ago. The study included 118 consecutive cases of prostate cancer treated with permanent prostate brachytherapy with Pd-103 by a single radiation oncologist between August 1997 and September 1999. Mean age of patients was 73 years (range 53-86 years). Mean prostate-specific antigen (PSA) was 9.25 ng/mL (range 1.3-73.88 ng/mL). The median Gleason score was 6 (range 3-8). Among T stage, 106 (90%) patients had ≤T2a, 10 (8.4%) had T2b, and 2 (1.6%) had T2c or higher disease. Unilateral disease was present in 81 (70%), and 35 (30%) had bilateral disease. The numbers of low-risk, intermediate-risk, and high-risk prostate cancer cases were 62 (52.5%), 44 (37.2%) and 12 (10.1), respectively. Brachytherapy as monotherapy was done in 100 (85%) patients, while 18 (15%) received supplemental external beam radiation therapy (EBRT) to a dose of 45 Gy delivered in 1.8-Gy fractions. Androgen deprivation therapy was used in 75 (64%) patients, mostly for less than 4 months, before the implant. For monotherapeutic approach with brachytherapy, the minimum peripheral dose with Pd-103 was 125 Gy and 90 Gy with boost brachytherapy. Patients were monitored by physical examination, including digital rectal examination and serum PSA determination at 3-6 month intervals for first 5 years and then on a yearly basis. All patients were assessed for clinical and biochemical recurrence based on the Phoenix definition. Kaplan-Meier analysis and curves were used to determine the cause-specific survival (CSS), biochemical progression-free survival (bPFS), and overall survival (OS). Follow-up ranged from 1 to 17 years with a median overall follow-up of 14 years and biochemical follow-up of 13 years for patients who are still alive. Overall median and biochemical follow-up was 11 years and 8 years respectively. A total of 29 cases had biochemical recurrence, with a biochemical control rate of 75%. Distant metastatic disease was documented in 3 patients. The 15-year bPFS for the entire cohort was 68%. The 15-year bPFS by risk group stratification was 75%, 61%, and 52% for low-, intermediate-, and high-risk patients, respectively. There was significant difference in bPFS between low-, intermediate-, and high-risk groups. The prostate cancer-specific survival rate was 97% at 15 years. The overall survival reached 50% at 15 years. Our long-term experience with Pd-103 based permanent prostate brachytherapy shows excellent efficacy as assessed by the 15-year cancer-specific and biochemical relapse-free survival.