Prostate Brachytherapy With Cs-131: Long-term Results Compared With Published Stereotactic Body Radiotherapy Data.

Objective: We sought to compare our results of patients treated with Cs-131 prostate brachytherapy (PB) as monotherapy to recently published results of patients treated with stereotactic body radiotherapy.

Methods: We analyzed data from patients treated at our institution with Cs-131 PB as monotherapy who had at least 5 years of follow-up and who prospectively completed expanded prostate cancer index composite questionnaires at baseline, 1 year, 2 years, and 5 years. We compared our data with the recently published data from radiation therapy oncology group (RTOG) 0938 and PACE-B (NCT01584258).

Results: A total of 138 patients were included in our cohort. Using RTOG 0938's definition, the frequency of a decline in urinary function in our PB cohort was 43% compared with 41.3% in RTOG 0938. According to PACE-B's definition, our PB cohort had minimal clinically important differences in the urinary incontinence domain of 26.4% and in the urinary obstructive/irritative domain of 40.7% at 2 years compared with PACE-B's reported rate of 32% and 33%, respectively. The frequency of a >5-point change in the expanded prostate cancer index composite bowel summary score at 5 years was 25% compared with 30.7% in RTOG 0938. Our bowel difference at 2 years was 23% compared with PACE-B's reported 24%. Our 5-year biochemical disease free survival (bDFS) was 97.8%, compared with 91.3% in RTOG 0938 and 95.8% in PACE-B.

Conclusions: Low dose rate (LDR) PB with Cs-131 as monotherapy provides excellent biochemical control of prostate cancer in low and intermediate-risk patients. Our cohort of patients had modest differences in patient-reported urinary and bowel quality of life compared with baseline. These differences were comparable to recently published stereotactic body radiotherapy data. When comparing prostate cancer treatments in terms of patient convenience and available resources, PB certainly should be considered.