PP03  Presentation Time: 9:38 AM: Prostate Brachytherapy with Cs-131: Long Term Results Compared to Published SBRT Data

Purpose Prostate brachytherapy (PB) as monotherapy has been established as a definitive treatment for low and favorable intermediate risk prostate cancer. Patients choose PB in part due to it being minimally invasive with a quick return to full activity. Recently, there has been growing interest in using shorter (ultrahypofractionated) radiotherapy regimens for the management of prostate cancer, citing the same rationale. We present data from a cohort of our patients treated with PB using Cs131 to compare our results with the 5-year data from the recently published SBRT trial from NRG Oncology RTOG 0938. Materials and Methods We analyzed data from patients treated at our institution who were treated with Cs131 LDR PB as monotherapy (115 Gy) and who prospectively completed EPIC questionnaires at baseline and at timepoints after the procedure including at 5 years. Urinary and bowel function was evaluated based on these EPIC scores exactly as they were in the recent 0938 publication, assessing the proportion of patients with a deterioration from baseline of >5 points for the bowel and > 2 points for the urinary score. We also report the bDFS in our cohort, calculated via the Kaplan Meier method. Results 138 patients were included in our analysis. Median patient age was 66 years old with a median follow up of 121.5 months. In terms of brachytherapy dosimetry, median prostate volume was 40.8 cc, median D90 was 104.3% and median V100 was 93.4%. The 5-year frequency for >2 point change in urinary score was 45.9% (61/133), compared to 41.3% in RTOG 0938. The 5-year frequency for >5 point change in bowel score was 30.7% (40/130), compared to 30.7% in RTOG 0938. Our 5-year bDFS was 97.8% (compared to 91.3% in RTOG 0938) and 96.0% at 10 years. 73 of our patients had low risk and 65 patients had intermediate risk disease, compared to all low risk patients in RTOG 0938. Conclusions LDR Brachytherapy with Cs131 as monotherapy provides excellent bDFS at 5 and 10 years, comparable to recently published outcomes with SBRT, especially considering that 47% of our PB patients had intermediate risk disease (compared to all low risk in the SBRT data). Our cohort of patients treated with PB had modest differences in patient-related urinary and bowel QOL at 5 years compared to baseline, also very comparable to published SBRT data. When comparing prostate cancer treatments in terms of patient convenience and available resources, PB certainly should be considered. Prostate brachytherapy (PB) as monotherapy has been established as a definitive treatment for low and favorable intermediate risk prostate cancer. Patients choose PB in part due to it being minimally invasive with a quick return to full activity. Recently, there has been growing interest in using shorter (ultrahypofractionated) radiotherapy regimens for the management of prostate cancer, citing the same rationale. We present data from a cohort of our patients treated with PB using Cs131 to compare our results with the 5-year data from the recently published SBRT trial from NRG Oncology RTOG 0938. We analyzed data from patients treated at our institution who were treated with Cs131 LDR PB as monotherapy (115 Gy) and who prospectively completed EPIC questionnaires at baseline and at timepoints after the procedure including at 5 years. Urinary and bowel function was evaluated based on these EPIC scores exactly as they were in the recent 0938 publication, assessing the proportion of patients with a deterioration from baseline of >5 points for the bowel and > 2 points for the urinary score. We also report the bDFS in our cohort, calculated via the Kaplan Meier method. 138 patients were included in our analysis. Median patient age was 66 years old with a median follow up of 121.5 months. In terms of brachytherapy dosimetry, median prostate volume was 40.8 cc, median D90 was 104.3% and median V100 was 93.4%. The 5-year frequency for >2 point change in urinary score was 45.9% (61/133), compared to 41.3% in RTOG 0938. The 5-year frequency for >5 point change in bowel score was 30.7% (40/130), compared to 30.7% in RTOG 0938. Our 5-year bDFS was 97.8% (compared to 91.3% in RTOG 0938) and 96.0% at 10 years. 73 of our patients had low risk and 65 patients had intermediate risk disease, compared to all low risk patients in RTOG 0938. LDR Brachytherapy with Cs131 as monotherapy provides excellent bDFS at 5 and 10 years, comparable to recently published outcomes with SBRT, especially considering that 47% of our PB patients had intermediate risk disease (compared to all low risk in the SBRT data). Our cohort of patients treated with PB had modest differences in patient-related urinary and bowel QOL at 5 years compared to baseline, also very comparable to published SBRT data. When comparing prostate cancer treatments in terms of patient convenience and available resources, PB certainly should be considered.