PURPOSE:We evaluate the effectiveness of radiation therapy (RT) dose constraints on bone in reducing the incidence of radiation-associated fractures in patients with LE-STS treated with image guided RT and modern treatment planning techniques. We had established these constraints as bone avoidance objectives for RT planning in 2005 after observing a 4.5% rate of bone fracture in patients. The ultimate goal is to improve functional outcome following external beam radiation therapy (RT) combined with limb salvage surgery for lower extremity soft tissue sarcomas (LE-STS) which can be associated with significant long-term complications, such as bone fractures, which can lead to multiple surgeries or amputation. METHODS AND MATERIALS:We retrospectively analyzed a prospectively maintained database of all patients with LE-STS who received curative-intent RT that was planned using evidence-based bone avoidance objectives between January 2005 and December 2020 at our institution. Using a standard bone volume contoured 2 cm above and below the planning target volume, the following RT planning objectives were extracted for patients with and without a fracture: mean dose to bone, RT treatment volume, maximum dose to bone, and volume of bone irradiated to ≥40 Gy (V40). Fracture site dose was determined by comparing radiographic images and surgical reports to fracture location on the RT plan with isodose distribution. Patient and tumor factors, treatment details, and patient survival were extracted from medical records and compared between the fracture and non-fracture patient cohorts. The χ2 test was used to analyze categorical variables, a Student ttest was used to analyze continuous variables and t test was used to compare means. Survival was estimated using the method of Kaplan-Meier. RESULTS:Between January 2005 and December 2020, 700 eligible patients were assessed, 594 patients (84.9%) received preoperative RT, 103 (14.7%) received postop RT, and 3 (0.4%) both. At a median follow-up of 55 months, 10 patients (1.4%) developed radiation-associated fracture. Two of these patients developed a fracture after reirradiation of the extremity and 2 of the remaining 8 patients did not meet the radiation dose bone constraints. Of the full cohort, 14 patients (2%) had an intramedullary nail and there was only one fracture in this subgroup. Twenty patients (2.8%) in the entire cohort required bone resection necessitating replacement with a prosthesis or an allograft. The mean time to fracture was 41.7 months. Fracture management varied from conservative treatment to amputation. Local recurrence occurred in 44 patients (6.3%) and 248 patients (35.4%) developed metastasis. CONCLUSIONS:The overall fracture risk after RT is reduced with modern planning techniques using the radiation dose constraints to a bone volume contoured 2 cm above and below the planning target volume. RT treatment planning for LE-STS should include a focus on limiting radiation dose to the bone to minimize the risk of fracture. For high-risk patients, prophylactic intramedullary nailing of the femur may help prevent radiation-associated fractures.

PURPOSE/OBJECTIVES:Low Dose-Rate Brachytherapy (LDR) and High Dose-Rate Brachytherapy (HDR) are options for favorable risk prostate cancer. We hypothesized that HDR provides comparable disease control with less urinary toxicity. Primary objective was to determine prostate cancer control at 48 months, defined as a PSA < 0.4 ng/ml. MATERIALS/METHODS:Eligible patients had low and intermediate risk diseases. Randomization was to Arm 1 LDR with I-125 to 144 Gy, or Arm 2 HDR with 19 Gy x1 + intraprostatic boost. Follow-up included PSA, toxicity (CTCAE v 4.0), and Quality of Life (EPIC 26). Arm 2 was closed in May 2019 due to evidence of inferior outcomes, and a third arm (HDR 13.5 Gy x 2) was opened. We report outcomes of Arms 1 (LDR) and 2 (HDR single fraction) prior to study amendment. RESULTS:103 patients were randomized: 51 to LDR (Arm 1) and 52 to HDR (Arm 2). Median age 65 years; 76 % had Gleason 3 + 4, 90 % PSA < 10, and 80 % stage T1c. Median follow-up 53 months. PSA control at 4 years was 78.4 % for LDR, and 21.2 % for HDR. Local progression rates: 2 % LDR, 13.5 % HDR. Grade 3 toxicity occurred in 6 patients for LDR and 2 patients Arm 2. Urinary irritative and bowel symptoms were worse in the first 6 months for LDR. CONCLUSIONS:LDR brachytherapy has high prostate cancer disease control rate at 4 years, although with worse impact on urinary symptoms in the first 6 months. Single fraction HDR was associated with unacceptable cancer control.

Purpose/Objective(s) To examine the feasibility of using a mobile phone app to remotely monitor patient-reported outcomes (PROs) during and immediately after radiation therapy (RT) for breast and prostate cancer. Materials/Methods English-speaking patients receiving RT for breast or prostate cancer were invited to participate in a single-center, longitudinal quality improvement project. Participants were asked to download a HIPAA/PHIPA compliant mobile phone app onto their personal device. Unsupervised participants used the app to report PRO-CTCAE at baseline, weekly during RT and up to 4 weeks after RT. Push notifications automatically delivered reminders to complete surveys. Participants were routinely seen by a radiation healthcare provider (HCP) once per week during RT. PROs were remotely monitored by Radiation Therapists during and after RT, with an intervention threshold of ‘moderate’ or greater symptom severity. The app also collected pre and post patient-centered communication data (PCC-Ca-6), and participant satisfaction. App use metrics were gathered from audit log timestamps (open and interacting). Results From July 2023 to Feb 2024, 20 prostate and 20 breast cancer patients participated (31% of the eligible population). The mean completion rate for all PRO surveys across all time points was 75%. Mean age was 64 (SD 14; range = 25-93) years, 50% were female, and 83% preferred to communicate in English. There were no statistically significant demographic differences between those who were: 1) enrolled and compliant (> 70% survey completion); 2) enrolled but poorly compliant (<70% completion); and 3) approached but chose not to participate (p > 0.7). During RT, PRO-CTCAE was reported 85 times (out of a possible 107), whereas HCPs documented 49 times using various quantitative scales (e.g. RTOG, ESAS). In the ‘post-RT’ period, PRO entries triggered early follow-up with 8 breast and 10 prostate patients. There were no significant differences between pre and post overall PCC-Ca-6 scores (mean: 110 vs. 108; p 0.35). On average, each patient logged into the app 16 times on 11 days. They spent an average of 7 minutes interacting with the app per session. At the end of the study, 65% of participants said they would recommend using the app to other RT patients. 7 participants voluntarily populated their personal app account with unsolicited details (e.g. other health conditions and symptoms). Conclusion These preliminary results suggest that remote monitoring of PROs entered via a mobile app is feasible during and immediately after RT. It is minimally burdensome to patients across a broad range of demographics and has no impact on their perceptions of patient-centered communication. A randomized controlled trial will now evaluate the use of remote PRO monitoring to triage attendance at in-person Oncologist review visits to identify the efficacy of a PRO-based personalized approach to providing supportive care.

Purpose/Objective(s) While carcinomas commonly metastasize to the brain, the incidence, and predictors of Brain metastases (BrM) in sarcoma patients remain poorly understood given their rarity. We aimed to determine the cumulative incidence (CI) and clinical factors associated with BrM in sarcoma patients. Materials/Methods We retrospectively analyzed data from all sarcoma patients who presented to our center between 2006 and 2023. The CI function was used to analyze time to BrM, with incidence stratified by key variables. Univariable (UVA) and multivariable analyses (MVA) were conducted to evaluate factors associated with BrM incidence. Results Among 3,766 sarcoma patients, 101 developed BrM. CI rates were 2.2%, 2.9%, and 3.3% at 24, 48, and 72 months, respectively, with a median time to BrM of 17 months. On UVA, intrathoracic and uterine primary locations, ASPS, Epithelioid, Intimal histologic subtypes, and metastatic stage at diagnosis were associated with increased CI of BrM. In contrast, age ≥ 59, primary retroperitoneal location and liposarcoma subtype were associated with a decreased CI. On MVA the following predictors remained significant: intrathoracic and uterine primaries (HR = 18.0, 95% CI = 8.52–38.0, P<0.001; HR = 6.72, 95% CI = 2.56-17.6, P<0.001), ASPS and Epithelioid Sarcoma (HR = 4.89, 95% CI = 2.17–11.0, P<0.001; HR = 2.77, 95% CI = 1.02–7.54, P = 0.047), age ≥ 59 years (HR = 0.45, 95% CI = 0.27–0.73, P = 0.001) and liposarcoma (HR = 0.12, 95% CI = 0.03–0.60, P = 0.009). Conclusion This report provides valuable insights into the CI of BrM among sarcoma patients, highlighting the impact of age, tumor location, and histologic subtype on BrM incidence. These findings underscore the importance of tailored surveillance for high-risk patients, potentially leading to improved outcomes.

Purpose/Objective(s) To report the outcomes of a prospective study of focal MR-guided HDR (MRgHDR) brachytherapy boost in combination with stereotactic body radiotherapy (SBRT) for localized prostate cancer. Materials/Methods Eligible patients included intermediate-risk (IR) and high-risk (HR) prostate cancer patients with visible gross disease (at 1 or more intraprostatic sites) comprising less than 33% of the total prostate volume on diagnostic MRI. Patients underwent either a 15 Gy single fraction MRgHDR focal boost to the gross disease followed by SBRT, 30 Gy/5 fractions for IR disease (prostate only) or 30 Gy/5 fractions for HR disease (prostate + pelvic nodes). Outcomes included PSA, toxicity (CTCAE v4), Health-Related Quality of Life (HRQoL) assessments (Expanded Prostate Cancer Index Composite (EPIC) [DK4][LB5]and were conducted at baseline, then at 1, 3, and 6 months, followed by 1, 2, 3, and 5 years. Androgen deprivation therapy (ADT) was administered based on the risk category. At a minimum of two years post-radiation, patients underwent a prostate MRI with or without a systematic biopsy to assess local disease status. Biochemical failure was defined according to the Phoenix definition (nadir + 2). Results Between 2017 and 2023, 153 patients were enrolled, with 128 (84%) having IR and 25 (16%) having HR disease. The median age was 69 years old (range 49-81), and the median PSA was 8ng/ml (2-53). ADT was administered in 46 (30%) patients. Among the IR patients who received ADT (25 patients), 21 (84%) patients received ≤ 6 months of ADT, while 4 (16%) patients received > 6 months of ADT. Of the 21 patients from the HR group, 3 (14%) patients received 6 months of ADT, and 18 (86%) received > 6 months of ADT. Hydrogel spacer insertion was used in 72 (47%) patients. The median follow-up was 36 months (range = 2-79). Median PSA nadir in patients without ADT was 0.35 (Range 0.01-4.75). Overall, the 3-year biochemical control rate was 96.5%, with 96% and 100% in the IR and HR groups. No isolated local failure was observed at 3 years. Three patients experienced local failure in conjunction with nodal relapse, and one patient had associated regional and distant failure. No isolated regional or distant failures occurred. At 1 month after treatment, the incidence of acute grade > 2 genitourinary (GU) and gastrointestinal (GI) toxicities were 13% and 2.6%, respectively. By 6-months, these rates decreased to 2.6% and 1.4% for GU and GI toxicity, respectively. Late grade ≥ 2 GU and GI toxicities at 1 year remained consistent at 2.6% and 0.7%. Notably, only one patient encountered severe toxicity (Grade 3 GU - hematuria attributed to radiation cystitis at 6 months), which subsequently resolved. Patients with a rectal spacer experienced slightly lower GI toxicity, which was not statistically significant. No difference in GI toxicity was seen in patients who received pelvic nodal irradiation when compared to the prostate-only patients. Conclusion Focal MRgHDR brachytherapy combined with SBRT demonstrated favorable tolerability and promising local and biochemical control.

Purpose/Objective(s) The PROFIT study was designed to evaluate hypofractionated (HF) radiotherapy versus conventional fractionation (CF) for patients with intermediate-risk prostate cancer (IR-PCa). Similar efficacy and toxicity outcomes were previously reported. Here the long-term patient-reported outcomes (PROs) following treatment are presented. Materials/Methods A total of 1206 men with IR-PCa were randomized to receive 78 Gy in 39 fractions over 8 weeks (CF) or 60 Gy in 20 fractions over 4 weeks (HF). PROs were evaluated at baseline, 24 and 48 months using the Expanded Prostate Cancer Index Composite (EPIC), American Urological Association Symptom Score (AUASS), and the 12-item Short Form Health Survey (SF-12) which combine 2 parts: a physical component summary (PCS) and a mental component summary (MCS). A minimally important difference (MID) was defined as a deterioration of domain- or subdomain-specific health-related quality of life (HRQoL) score at each time point compared to baseline ≥ 0.5 standard deviation. Wilcoxon’s rank sum test was used for comparing all continuous measures, and Pearson’s Chi-squared test was used for comparing MID between two arms at each visit. Statistical significance was declared only when P < 0.01. Statistical analyses were performed using R version 4.3.0. Results At baseline, 87.9% of patients in the CF and 88.5% in the HF arm provided completed forms dropping to 76.5% and 77.9% at 48 months, respectively. AUASS was similar and stable (median of 5) over time in both arms (P > 0.2). No significant differences were found between the two arms in the urinary, bowel, sexual and hormonal domains or subdomains at any time point (P > 0.02). The greatest decline over time occurred in sexual domain, decreasing ≥ 10 points from baseline to 24 months in both arms. SF-12 means of both, PSC and MSC, were similar and remained stable at all time points. At 24 months, MSC summary was significantly higher in CF arm (46 in CF arm vs 45 in HF arm; P = 0.005), but not maintained at 48 months. The proportion of patients reporting MID was similar in both arms across all scores except in the bowel function at 48 months, where there was a significant difference in favor to the HF arm (51.5% in CF arm vs 39.5% in HF arm; P = 0.001) and a trend in bowel summary (53.4% in CF arm vs 44% in HF arm; P = 0.01) Overall treatment satisfaction was high in both arms, ≥ 88% of patients were either satisfied or extremely satisfied with treatment. Conclusion Findings from the PROFIT study suggest no differences in urinary, bowel and sexual HRQoL between CF and HF. However, the proportion of patients reporting MID in bowel function at 48 months was significantly higher in the CF arm. At 24 months SF-12 MCS were significantly higher in the CF arm but no longer present at 48 months.

Purpose/Objective(s) To evaluate the outcomes of conventional preoperative radiation therapy (preop-RT) followed by surgery for soft tissue sarcoma (STS) of the extremity and trunk. Materials/Methods A retrospective review was conducted using a prospectively maintained database of STS patients from a single sarcoma center (11/2000 - 09/2020). All patients underwent conventional preop-RT (50 Gy/25 fractions) utilizing either 3D-Conformal Radiation Therapy (3D-CRT) or Image-Guided Intensity Modulated Radiation Therapy (IG-IMRT), followed by surgery after 4-6 weeks. The primary focus was major wound complications (MWC) rates and oncological outcomes. The long-term functional outcome was assessed using the Musculoskeletal Tumour Society Rating Scale (MSTS) and the Toronto Extremity Salvage Score (TESS). Results Median follow-up was 5.9 (0.5-24.6) years among 1140 patients, of whom 761 had IG-IMRT and 379 had 3D-CRT. The most common histologies were myxofibrosarcoma (13%), undifferentiated pleomorphic sarcoma (11%), and myxoid liposarcoma (11%). Tumors>10 cm were observed in 32% (360/1125), and 88% (960/1090) had grade II-III tumors. Positive microscopic margins were found in 15% (166/1137) of patients. The overall incidence of MWCs was 24% (271/1110), with 28% for 3D-CRT and 23% for IG-IMRT (p = 0.077). Comparative analysis of the IG-IMRT and 3D-CRT cohorts revealed no significant differences in 5-year local recurrence rate (6.0% vs 4.8%; p = 0.549), 5-year disease-free survival (69% vs 70.1%; p = 0.519), 5-year overall survival (78.5% vs 76.3%; p = 0.195), and 5-year distant metastatic rate (27% vs 26.6%; p = 0.590), respectively. Additionally, the multivariable analysis indicated that 3D-CRT, large tumor size (>10 cm), and tumors located in the lower extremity significantly increased the risk of MWCs, with odds ratios of 1.40 (95% CI = 1.04-1.89; p = 0.025), 1.49 (95% CI = 1.11-1.99, p = 0.008), and 2.84 (95% CI = 1.86-4.33, p<0.001), respectively. There was no significant difference in TESS and MSTS scores between IG-IMRT and 3D-CRT, with mean overall scores of 84.5 and 83.6 (p = 0.73) and 89.4 and 86.4 (p = 0.35), respectively. Conclusion Conventional preop-RT followed by surgery provided favorable outcomes for STS patients with acceptable MWC rates. IG-IMRT may be the preferred RT technique due to its marginally lower MWC rates. These findings may provide a contemporary (conventionally fractionated) standard for comparison with new hypofractionated preoperative RT protocols.

Purpose/Objective(s) The integration of stereotactic body radiation therapy (SBRT) into the treatment paradigm of metastatic bladder cancer may represent a provocative approach. The SABR-COMET trial reported improved overall survival (OS) in oligometastatic patients treated with SBRT but the bladder cancer population was underrepresented. We report the clinical outcomes of patients with metastatic bladder cancer treated with SBRT in a Canadian population. Materials/Methods From a prospectively collected database registered in the Canadian Bladder Cancer Information System, we identified patients with oligometastatic or oligoprogressive bladder cancer treated with SBRT ≥ 5 Gy/fraction or palliative radiotherapy (PRT) defined as 6-8Gy in 1 fraction or 20Gy in 5 fractions to at least one metastatic index lesion from 2015 to 2024. Outcomes of interest were overall survival estimated using the Kaplan-Meier method and treatment-related adverse events (TAE). Results We identified 183 patients who received SBRT or PRT. Of these, 107 patients (58.5%) received PRT, with 89 PRT alone and 13 receiving PRT + immunotherapy. The most common locations treated were bone (62%), followed by soft tissue and lung (14%) and others (24%). The median follow-up time was 537 days (IQR = 599) for SBRT and 503 days (IQR = 568) for PRT. Overall survival (OS) at 24 months was 85.5% for SBRT versus 56% for PRT, [HR = 0.64 (0.44–0.91) (P = 0.014)]. A sub-analysis of OS comparing SBRT alone versus SBRT + Immunotherapy showed no significant difference (P = 0.247). The incidence of TAE in the entire cohort was 5.46% for gastrointestinal and 1.9% for genitourinary events. Conclusion SBRT with or without immunotherapy appears to be associated with better OS compared to PRT (+/- immunotherapy), The rate of recorded adverse events was low overall. While there is likely a bias in selecting patients with better prognosis for SBRT, these findings warrant further investigation to establish a more comprehensive understanding of the role of SBRT and its clinical implications for this patient population. The interplay between SBRT and immunotherapy likewise needs further study given the known immunogenicity of the large dose/fraction normally employed in this setting.

Purpose/Objective(s) Machine learning (ML) radiotherapy (RT) treatment planning has shown improved efficiency while maintaining quality. However, there has been no prospective evaluation of patient outcomes when using ML as standard-of-care for RT planning, thereby limiting the assessment of its value proposition. We hypothesized that minimal clinical differences in genitourinary (GU) and gastrointestinal (GI) toxicities exist between ML- and human-generated RT plans during prospective application. Materials/Methods We prospectively evaluated ML- and human-generated plans for curative-intent prostate RT (60 Gy in 20 fractions) in a cohort of 113 consecutive patients treated between November 2019 and June 2022. We employed a previously institutionally developed, validated, and clinically implemented dose prediction ML model functioning within a commercial RT planning system. ML planning, without any manual adjustments, was the default planning method used in all cases. Radiation oncologists either approved the ML plan or requested an alternative human-generated plan for direct comparison, and then selected the preferred plan for treatment. GU and GI toxicities with minimum follow-up of 180 days were collected for all patients. We performed a toxicity-free survival Kaplan-Meier analysis for grade 2+ GU and grade 2+ GI toxicities between ML- and human-generated plans, and comparisons were based on log-rank tests. Results In the prospective standard of care ML deployment study, radiation oncologists selected ML plans for clinical treatment in 86 cases (76%) and selected human plans in 27 cases (24%). For cases in which a human-generated plan was requested, the ML plan was selected for treatment in only one case. In terms of treatment outcomes, there were no treatment-related grade 2+ GI toxicities observed and no significant differences in toxicity-free survival were observed for GU grade 2+ toxicities between ML- and human-generated plans (P = 0.39). Conclusion This is the first study demonstrating that dose prediction ML planning maintains low levels of toxicity in curative-intent prostate cancer and encourages the clinical translation of this technology into practice. When appropriately validated and deployed, ML planning can retain good clinical outcomes while improving efficiencies and can be safely used as standard of care applicable to the majority of patients, with a human-in-loop strategy.

MRgHDR brachytherapy boost in conjunction with EBRT provides comparable biochemical outcomes compared to the literature. Severe toxicity rates were minimal. Further follow-up will determine if these outcomes are sustained.

In MIBC standard staging with CT imaging is critical for making treatment decisions about neoadjuvant chemotherapy (NAC), and local treatment with either radical cystectomy (RC) or chemoradiation. However, CT imaging can often underestimate disease extent. The aim of this randomized study was to determine if adding 18F-FDG PET/CT (PET) to baseline CT, changes treatment received. Newly diagnosed MIBC pts (T2a-T4, N0-3, M0) without metastases on baseline CT, and predominant urothelial histology, were allocated 2:1 to PET or no further imaging. Enrollment occurred 05/16-11/21 at 6 Ontario centers. At the time of analysis, median duration of follow-up was 2 years. Primary outcome was proportion of pts not receiving expected treatment and secondary outcomes were disease-free survival (DFS) and overall survival (OS). Of 292 pts, 194 were randomized to PET and 98 to no PET. In the PET and no PET arms respectively: median age was 70 (43-93) and 68 (42-89); T2: 77% and 77%; node negative 88% and 87%; planned RC 66% and 69%; and planned NAC 70% and 64%. On PET, primary bladder tumor was seen in 86 (47%) pts, positive pelvic lymph nodes in 37 (20%), distant nodes in 32 (18%) and distant metastases in 13 (7%). By ITT analysis, 166 (86%) PET pts received expected treatment, 21 (11%) did not and 7 (4%) withdrew/died prior to treatment. In the no PET arm, 90 (92%) received expected treatment, 4 (4%) did not, and 4 (4%) withdrew/died prior to treatment. More PET pts were deemed palliative 18 (9.3%) vs 3 (3.1%). Notably >60% in both arms received NAC. PET pts were more likely to have a change in treatment, odds ratio 2.89 (95% CI 0.96-8.74, p=0.06) compared to CT alone. No statistically significant difference was observed between arms for DFS (HR=0.78, 95% CI 0.55-1.12) or OS (HR=1.02, 95% CI 0.66-1.56). In this large randomized study, there was a trend towards a change in management in pts having a PET, but this did not reach statistical significance. This trial provides new insights into the clinical utility of PET-CT in MIBC.

Purpose/Objective(s) Focal therapy has gained traction in the management of localized prostate cancer (PCa) based on the promise of equivalent oncologic outcomes with minimal toxicity compared to whole gland therapy. However, 20-45% of patients have persistent/recurrent disease within the first 2-5 years after most commonly-used ablative methods (e.g., HIFU, cryotherapy). Based on brachytherapy's (BT) well-established and long track-record of efficacy for PCa, we sought to test the focal therapy hypothesis in a prospective clinical trial of MR-guided HDR for men with localized PCa. Materials/Methods This prospective trial was approved in 2016 (UHN IRB# 16-5490; NCT02918253) for patients with clinically low- and favorable intermediate-risk prostate cancer, and a conspicuous lesion on mpMRI consistent with the area of pathological involvement. The CTV was derived from the mpMRI-defined GTV plus a 7 mm isotropic expansion, with 2 mm sup/inf added for the PTV. Implant and planning were performed with an MR-only workflow, and delivery with HDR BT. Treatment consisted of two separate implants within 14 days, to a prescription dose of 33-36 Gy in 2 sessions (BED ≥ 200 Gy). Biochemical recurrence (BCR), defined as > 2ng/mL above nadir was calculated using the Kaplan Meier method. Local failure, distant metastasis (DM) and toxicity events are reported as absolute rates. Results Nineteen patients have been treated, with a median age of 73 years (range 48-84), and median follow-up of 24 months (8-63). Median PSA was 6.1 ng/mL and 17/19 patients had Grade Group 2 disease. On average, the GTV and PTV corresponded to 3.56% (1.58-12.07) and 23.16% (13.71-40.75) of the median prostatic volume (40.49 cc [25.57-97.6]). Median number of catheters was 7 (4-11). Median GTV D99 and PTV D95 per fraction were 23.82 Gy (18.50-31.89) and 18.71 Gy (16.01-20.64), respectively. Nine patients have undergone the 2-yr local control ascertainment; 7 with mpMRI plus biopsies, and 2 with mpMRI only. At 2-years, local control and BCR-free survival were 100%; a single BCR event has been recorded 34 months after treatment. No DM or death events have occurred. The rate of treatment-related acute and late toxicities that were graded ≥ 2 was 0%. Conclusion Focal MRI-guided HDR brachytherapy as monotherapy appears to have a high therapeutic ratio and is a promising technique for localized PCa. Further follow-up will determine the durability of outcomes with this approach and the need for collaborative randomized studies.