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.

BACKGROUND We sought to assess the impact of bladder neck dose (BND) on patient reported urinary toxicity, and feasibility of relative urethral sparing technique in prostate brachytherapy (PB). METHODS AND MATERIALS We retrospectively identified bladder neck as a point dose on post-implant CT scans in patients treated with 131Cs PB. Urinary symptoms were assessed through EPIC questionnaires. Patient cohorts were identified based on mean BND as a percentage of prescription dose with toxicity assessment at each time point. RESULTS In our cohort of 542 patients, BND was associated with clinically significant acute urinary symptoms and chronic symptoms, as patients receiving >70% of the prescription dose had significantly worse overall EPIC scores than patients receiving ≤70% of prescription dose. There was no difference in bDFS between patients receiving BND ≤70% (96% bDFS) and >70% (94% bDFS) at a median follow up of 57 months. CONCLUSIONS BND has a significant impact on both acute and chronic urinary symptoms, with reduced symptoms reported with BND <70% of prescription dose. With a median follow up of 4.7 years, excellent bDFS has thus far been achieved with relative urethral and bladder neck sparing. Utilizing this constraint should improve urinary symptoms without impacting disease control.

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.

Single modality PB with Cs131 provides excellent long-term bDFS, especially when compared to recently published RTOG 0938 as 47% of our patients had intermediate-risk disease (RTOG 0938 had low-risk disease only and only 5-year data). Our patients had modest changes in urinary and bowel QOL compared to baseline, also comparable to published SBRT data. At 5 years in our cohort, 46% and 41% reported improvement in their urinary and bowel EPIC scores. The reason for this needs to be explored.

PURPOSE: This study evaluates long-term patient-reported bowel quality of life (QOL), rectal bleeding, and bleeding bother in patients with prostate cancer treated with external beam radiation therapy (EBRT) and Cesium-131 LDR brachytherapy (LDR-BT) boost with and without hydrogel rectal spacer.METHODS AND MATERIALS: This is a retrospective analysis of prostate cancer patients treated between 2007 and 2022 with 45 Gy EBRT followed by 85 Gy Cs-131 LDR-BT boost with or without hydrogel rectal spacer. Expanded Prostate Cancer Index Composite (EPIC) QOL questionnaires pre-treatment and at each follow-up were collected. Patient-reported rectal bleeding occurring more than "rarely" and bother from rectal bleeding occurring more than a "very small problem" were deemed clinically significant. Fisher's exact test was used to test the association of rectal spacer use and the incidence of clinically significant rectal bleeding and bleeding bother. Paired samples t-test was used to analyze mean bowel scores at each time point.RESULTS: Three hundred and forty-one patients were included in the analysis. The rectal spacer was used in 108 patients. Overall median follow-up was 48 months (IQR, 24-72), with a median follow-up of 24 months (IQR, 12-37.5) for the hydrogel group and 60 months (IQR, 36-84) for the non-hydrogel group. EPIC questionnaire response rates at median follow-up were 33% and 37% for the hydrogel and non-hydrogel groups, respectively. A clinically significant decrease in mean bowel domain scores was seen in the bowel bother domain at 6 and 12 months for patients who did not receive a rectal spacer. At the last follow-up of 60 months, the prevalence of clinically significant rectal bleeding and bleeding bother were 2.2% and 2.2%, respectively. The cumulative incidence of clinically significant long-term rectal bleeding was 2.8% and 18.9% in the hydrogel group and non-hydrogel group, respectively (Fisher's exact test, p < 0.0001). The cumulative incidence of clinically significant long-term bowel bother was 4.6% and 19.7% in the hydrogel group and non-hydrogel group, respectively (Fisher's exact test, p < 0.001).CONCLUSIONS: Use of hydrogel rectal spacer with EBRT and Cs-131 LDR-BT boost was significantly associated with a lower incidence of patient-reported rectal bleeding and bother from rectal bleeding, and better long-term bowel QOL. Cumulative incidence was 2.8% (hydrogel group) versus 18.9% (non-hydrogel group) and 4.6% (hydrogel group) versus 19.7% (non-hydrogel group) for clinically significant long-term rectal bleeding and long-term bleeding bother, respectively.(c) 2023 American Brachytherapy Society. Published by Elsevier Inc. All rights re-served.

Long-term patient-reported clinically significant decreases in urinary function and urinary incontinence mean EPIC scores occurred up to 18 months following combined external beam radiation and Cs-131 prostate brachytherapy and returned to baseline at 24 months, while clinically significant decrease in urinary irritability/obstructive mean scores occurred at 9 months and returned to baseline at 12 months. At 42 months follow-up, mean urinary domain scores improved from pre-treatment baseline in 15-30% of patients.

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.

Purpose To evaluate long-term patient reported rectal bleeding in patients with prostate cancer treated at our institution with and without SpaceOAR following external beam radiation therapy and Cesium-131 (131Cs) prostate LDR brachytherapy boost. Materials and Methods We started routinely offering SpaceOAR to patients treated with external beam radiation therapy and 131Cs prostate LDR brachytherapy boost from 2016 with goal of potentially reducing rectal toxicity, including late rectal bleeding. We analyzed patients treated with and without SpaceOAR with at least 6 months of follow-up, with treatment from January 2007 to February 2021. Patients were asked to fill out Expanded Prostate Cancer Index Composite (EPIC) QOL questionnaire pre-treatment and at each scheduled follow-up appointment. The EPIC questionnaire included the following categories related to rectal bleeding and bother from rectal bleeding. Rectal bleeding occurring more than "rarely" was deemed clinically significant and severe rectal bleeding was defined as occurring "usually" or "always". Clinically significant bother from rectal bleeding was defined as considering bleeding to be more than a "very small problem." Severe bother from rectal bleeding was defined as being a "moderate" or "big" problem. Univariate Cox regression was performed to assess for impact of SpaceOAR on incidence of clinically significant rectal bleeding, with censorship at maximum follow-up. Results 317 patients were included in the analysis, all of whom were treated with a combination of external beam radiation therapy and LDR brachytherapy boost. 172 patients (54.3%) had intermediate-risk prostate cancer, while 145 patients (45.7%) had high-risk disease. 157 patients (49.5%) received androgen deprivation therapy, while 160 patients (50.5%) did not. 87 patients (27.4%) underwent prostate LDR brachytherapy boost with SpaceOAR inserted in the operating room following completion of prostate seed implant, with remaining 230 patients (72.5%) treated without SpaceOAR. Median follow-up for patients who received SpaceOAR was 18 months (IQR 12-30 months), whereas median follow-up for patients who did not receive SpaceOAR was 54 months (IQR 36-72 months). Incidence of acute clinically significant rectal bleeding, occurring before 6 months, was 3.9% in the cohort treated without SpaceOAR and 3.4% in the cohort treated with SpaceOAR. Incidence of late clinically significant rectal bleeding was 19.6% without SpaceOAR and 0% with SpaceOAR. For patients who developed late clinically significant rectal bleeding, median time to development was 18 months (IQR 9-24 months). Prevalence of late clinically significant rectal bleeding at last follow-up was 3.5% without SpaceOAR. Incidence and prevalence of late severe rectal bleeding without SpaceOAR was 4.7% and 1.3%, respectively. Incidence of late clinically significant bother from rectal bleeding was 20% without SpaceOAR and 0% with SpaceOAR. Prevalence of late clinically significant bother from rectal bleeding at last follow-up was 4.3% without SpaceOAR. Incidence and prevalence of late severe bother from rectal bleeding without SpaceOAR was 10.9% and 2.2%, respectively. On univariate analysis, SpaceOAR utilization was significantly associated with reduction in incidence of clinically significant rectal bleeding (p=0.035, hazard ratio 0.033; 95% confidence interval 0.001-0.784). Conclusions Overall prevalence of late rectal bleeding following 131Cs LDR prostate brachytherapy at last follow-up was less than 5%. SpaceOAR was associated with lower incidence of clinically significant rectal bleeding occurring at 6 months post-treatment or later as assessed by the EPIC questionnaire. Given the lower median follow-up in the SpaceOAR group, additional follow-up is warranted to determine whether this reduction is maintained long-term.

PURPOSE: To evaluate short-term patient reported urinary quality of life scores in patients with prostate cancer treated at our institution with and without perioperative prednisone following Cesium-131 (Cs-131) prostate LDR brachytherapy. METHODS AND MATERIALS: We started routinely using a perioperative 7-day course of prednisone at a dose of 5 mg per day, beginning 1 day prior to Cs-131 prostate LDR brachyther-apy from 2013 with goal of improving acute urinary symptomatology. One hundred consecutive patients treated with prednisone were selected, with comparison to 100 consecutive patients who were not treated with prednisone. We analyzed for differences in mean change with standard deviation (SD) in EPIC and AUA scores at 0.5-1 month and 3 months with or without pred-nisone by Mann-Whitney U Test. Binary logistic regression was performed to assess for impact of prednisone on postoperative urinary catheter use. RESULTS: Pretreatment EPIC and AUA scores were available in 197 patients. Less reduction in EPIC US score was noted at 0.5-1.0 month in the group who received prednisone with mean change of-22.9 (SD 15.4) when compared to the group who did not receive prednisone with mean change of-31.7 (SD 19.3), p < 0.01, with significance lost at 3 months. There was no significant difference in acute urinary retention requiring postoperative urinary catheter placement with perioperative prednisone (OR 1.13, p = 0.71). CONCLUSIONS: A short course of perioperative low-dose prednisone was associated with less severe worsening in urinary symptoms by the EPIC questionnaire at the 0.5-1.0-month timepoint suggesting some improvement in acute urinary quality of life, although differences did not re-main statistically significant at 3 months.(C) 2022 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

PURPOSE: To evaluate our institutional outcomes utilizing Cs-131 prostate brachytherapy (PB) for the intermediate-risk (IR) group of prostate cancer patients. METHODS AND MATERIALS: We reviewed a prospectively collected database of men treated with Cs-131 PB between 2006 and 2019. Patients with less than 24-months follow-up were excluded. Patients were classified as IR if they had one of the following factors: Gleason Score 7, prostate specific antigen > 10 but < 20 ng/mL, or T2b-c on clinical exam. We defined unfavorableIR (UIR) as having either Grade Group 3, > 1 IR factors, or >50% positive core biopsies. The Kaplan-Meier method was used to estimate actuarial event-time probabilities for biochemical freedom from disease (BFD). RESULTS: A total of 335 patients with a median follow-up of 70.1 months (IQR 48.3-106.3 months) were identified. Androgen deprivation therapy (ADT) was used in 7.2% of patients. Favorable-IR (FIR) patients were commonly treated with PB alone (91.8%). FIR patients who underwent PB alone had a 5-year BFD of 98.1%. UIR patients were commonly treated with external beam radiotherapy plus PB (61.2%). These patients had 5-year BFD of 91.1%. The 5 year BFD for UIR patients treated without ADT was 90.9%, whereas it was 95.0% among UIR patients treated with ADT (log-rank p = 0.83). CONCLUSIONS: FIR patients have excellent outcomes when treated with PB alone. External beam radiotherapy plus PB is a reasonable treatment approach for UIR patients. Future studies may elucidate which IR patients would benefit from treatment intensification. (C) 2021 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

237 Background: Vigneault et al. reported that baseline intraprostatic calcification (IC) was associated with a higher risk of biochemical recurrence (BCR) in men treated with I-125 prostate brachytherapy (PB). Cs-131 has different physical properties than I-125. We assessed whether baseline IC was associated with BCR in men treated with Cs-131 PB. Methods: We retrospectively reviewed the records of all low-risk (LR), favorable intermediate-risk (FIR), and unfavorable IR (UIR) prostate cancer patients treated with Cs-131 PB +/- external beam radiotherapy (EBRT) from 2/2011 to 7/2018 at our institution. Patients who received hormone therapy or those with < 24 months follow-up were excluded. Baseline IC status (defined as 1 or more ICs ≥ 5 mm) and characteristics were determined on post-PB CT scans. Baseline patient characteristics were compared via χ2, Mann–Whitney U, or Student’s t-test. Predictors of BCR (Phoenix definition) were analyzed via Cox proportional hazards model and Kaplan–Meier survival curves were generated. Results: Two hundred and sixteen LR, FIR, and UIR prostate cancer patients treated with Cs-131 PB +/- EBRT were included. Median follow up was 56.9 months (range 24.1–111.4 months). 76 patients (35.2%) had baseline IC and 140 patients (64.8%) did not. Baseline disease characteristics did not differ significantly between patients with vs. without ICs. In patients with baseline IC, the median number of ICs was 1 (range 1–3), median length of largest IC was 9.1 mm (range 5.0–33.1), and median peak density of largest IC was 884 Hounsfield units (range 283–1744). ICs were most commonly present in the midgland (88.2%) and central (97.4%) regions. On univariate Cox analysis of all baseline disease, treatment, and IC characteristics, only initial PSA (p = 0.016) and NCCN risk group (p = 0.047) were significant predictors of BCR, whereas baseline IC was not (p = 0.11). The 5-year BCR-free survival in patients with vs. without baseline IC was 97.7% vs. 93.8% (p = 0.40), respectively. Conclusions: In a cohort of LR and IR prostate cancer patients treated with Cs-131 PB, the rate of BCR in men with baseline IC was low and baseline IC was not associated with a higher risk of BCR.

PURPOSE: This study evaluates acute patient-reported bowel quality of life (QOL) and rectal bleeding in prostate cancer patients treated with combination external beam radiation (EBRT), low-dose-rate brachytherapy (LDR-BT), and SpaceOAR. MATERIALS AND METHODS: A retrospective review of prostate cancer patients treated with EBRT (45 Gy), cesium-131 LDR-BT (85 Gy), and SpaceOAR was conducted. Patient-reported acute (<= 3 months after LDR-BT) bowel QOL and rectal bleeding was analyzed from Expanded Prostate Cancer Index Composite (EPIC) questionnaires. Five-point changes in mean bowel QOL scores were considered clinically significant. Clinically significant rectal bleeding was bleeding occurring more than "rarely'' ("about half the time,'' "usually,'' or "always''), and clinically significant bleeding bother was considering bleeding a "small, moderate, or big problem.'' Outcomes were analyzed using descriptive statistics and paired t-tests. RESULTS: 69 patients were identified. Bowel summary, function, and bother scores clinically and significantly decreased 2 weeks after LDR-BT (79.9 +/- 15.6, 80.5 +/- 15.4, and 79.4 +/- 18.1, respectively) compared with pre-EBRT scores (92.3 +/- 9.1, 93.3 +/- 9.0, and 92.6 +/- 11.9, respectively) and pre-LDR-BT scores (91.1 +/- 11.0, 91.6 +/- 9.8, and 90.6 +/- 13.3, respectively), but returned to clinical and statistical baseline pre-EBRT values at 3 months (88.7 +/- 12.4, 88.8 +/- 11.1, and 88.7 +/- 14.5, respectively). The 3-month cumulative incidence of clinically significant rectal bleeding and bleeding bother was 4.35% and 2.90%, respectively. CONCLUSIONS: With combination EBRT, LDR-BT, and SpaceOAR, bowel QOL returned to the baseline 3 months after LDR-BT. Clinically significant rectal bleeding was <5%. Further followup will confirm if low acute rectal toxicity translates to reduced late toxicity. (C) 2020 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

AIMS: To report on the PSA outcomes in men undergoing prostate seed implant (PSI) with Cesium-131 at a single institution. MATERIALS AND METHODS: All patients who underwent prostate brachytherapy with Cesium-131 (Cs-131) at our institution and had the potential for at least 24 months of follow up were included in this study. Results are reported for the by NCCN risk group (low, low/high-intermediate, and high), as well as by treatment received (monotherapy, combination external beam radiation + PSI, or trimodal therapy with androgen deprivation). The Phoenix definition (absolute nadir plus 2 ng/mL) was used to define biochemical freedom from disease (BFD). RESULTS: Eight hundred and six men have undergone prostate brachytherapy with Cesium-131 at our institution, and 669 men were included in analysis. Median follow up was 60.0 months (range: 0-144 months). According to NCCN risk categories, 29.9% were low-, 55.6% intermediate-, and 14.5% high-risk. Using the Phoenix criteria, 5/10-year BFD was 97.1/95.3% for patients in the low-risk category, 94.0/90.1% for patients in the intermediate-risk category, and 86.2/56.6% for patients in the high-risk category. PSA <= 0.2 ng/dL at 4 years was predictive of 10 year biochemical control: 96.3% vs 70.4%, p < 0.001. CONCLUSIONS: The present study demonstrates that prostate brachytherapy with Cs-131 achieves excellent long-term biochemical control. (C) 2020 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

The intermediate-risk (IR) group of prostate cancer patients is extremely heterogenous. Patients are sub-classified into favorable-IR (FIR) and unfavorable-IR (UIR) groups due to variable prognoses, leading to significant treatment variations. We sought to evaluate our institutional outcomes utilizing Cs-131 prostate brachytherapy (PB) for IR patients and elucidate which factors are important for driving more aggressive treatment. We reviewed a prospectively collected database of men treated with Cs-131 PB between 2006-2019. Patients with less than 24-months follow-up were excluded. Patients were classified as IR if they had one of the following factors: Gleason Score 7, prostate specific antigen (PSA) >10 but < 20 ng/mL, or T2b-c on clinical exam. We defined UIR patients as having either Grade Group (GG) 3 or >1 IR factors. Our general treatment schema was to treat FIR with PB alone (115 Gy) and UIR with combined external beam radiation therapy (EBRT) to 45 Gy + PB boost (85 Gy), though this was somewhat variable. The Kaplan-Meier method was used to estimate actuarial event-time probabilities for biochemical failure (BF). BF was defined as a serum PSA at least 2 ng/mL greater than posttreatment nadir PSA. Cox regression analysis was performed to identify predictors for BF. These factors included: GG, UIR subgroup, treatment (PB alone vs combined modality), ADT use, age (≤67 vs >67), clinical T-stage, PSA (<10 vs ≥10-20), and >1 IR factors. A total of 327 patients with a median follow-up of 70.6 months (IQR 45.9-102.7 months) were identified. Median age was 67 (IQR 62-72). ADT was used in 12.5% of patients. Most patients (57.5%) were classified as FIR. Of the 139 patients in the UIR subgroup, 69.1% met UIR criteria by virtue of GG 3 only and 30.9% by having >1 IR factor. Twenty-eight patients (20.1%) had a GG 3 and >1 IR factor. FIR patients had a 5-year BF rate (BFR) of 2.5% (SE 0.012). The 5-year BFRs for FIR patients treated with PB alone (81.4%) and combined modality (18.6%) were 1.7% (SE 0.012) and 5.0% (SE 0.035), respectively (p = 0.18). UIR patients had a 5-year BFR of 10.9% (SE 0.030) and were most commonly treated with EBRT+PB (61.9%). Five-year BFRs were 14.0% (SE 0.078) and 10.1% (SE 0.032) for UIR patients treated with PB alone and combined modality, respectively (p = 0.91). UIR patients by virtue of GG 3 only (n = 68) had a 5-year BFR of 13.0% (SE 0.047). The 5-year BFR for UIR due to >1 IR factors (n = 71) was 8.9% (SE 0.038). Six patients had 3 IR factors with a 5-year BFR of 50% (SE 0.25). On multivariate analysis, UIR subgroup was the only significant predictor for BF (p = 0.02; HR 2.49, 95% CI 1.15-5.41). The FIR subgroup is a distinct entity from the UIR subgroup with excellent outcomes when treated with Cs-131 PB alone. UIR patients have excellent outcomes with combined EBRT + PB. The majority of UIR patients do not require ADT, though the group that would benefit still needs to be defined.