Background Since the inception of spinal radiosurgery decades ago, the factors influencing spinal cord recovery have remained unclear. Elucidating these factors would aid in reirradiation planning and delivery. We describe modeling reirradiation normal tissue complication probabilities (NTCP) from compiled published data, akin to the collaborative Quantitative Analysis of Normal Tissue Effects in the Clinic (QUANTEC) and High Dose per Fraction, Hypofractionated Treatment Effects in the Clinic (HyTEC) projects.Purpose Simple dose-time recovery factors for the spinal cord serve as a basis to propose the Reirradiation Treatment Effects in the Clinic (ReTEC) project. ReTEC aims to define human organ recovery factors to convert the total composite dose to an equivalent physical dose compatible with the de novo therapy dose tolerance limits. Additionally, we present a system for automating analyses as well as clinical implementation of radiation dose-time recovery.Methods Published literature was queried for stereotactic voxel-wise composite reirradiation plans involving the spinal cord, but none were found. Hence, minimum reporting criteria were used instead: spinal cord maximum dose (Dmax) of each course, time interval between courses, and number of fractions or biologically effective dose, per patient or in sufficiently homogeneous groups of patients. Recovery factors and logistic model parameters were fitted with maximum likelihood techniques.Results An NTCP model was derived from 13 papers with data from 282 lesions, including six myelopathy cases. The model suggested spinal cord recovery of more than 50% in less than 1 year, which is faster and more complete than current clinical practice, but with wide confidence intervals (CI) (bootstrap 95% CI: 31%-95% when the time interval was 1 year).Conclusion Due to limited data, we recommend remaining within current standard guidelines until more comprehensive analyses, optimally under the ReTEC initiative, refute or validate these estimates. ReTEC would require composite plans accounting for differing Dmax locations in each course. Nevertheless, this proof-of-concept Dmax model provides insight and serves as a basis to propose ReTEC.

Indeterminate lesions on prostate-specific membrane antigen (PSMA)-PET are challenging to address. We aimed to develop, implement, and evaluate a multidisciplinary consensus algorithm that integrates existing interpretation systems with multimodality imaging and clinicopathological information for interpreting indeterminate bone and lymph node lesions on PSMA-PET. This was a retrospective single-center study on a prospectively implemented algorithm. We included all consecutive prostate cancer patients whose PSMA-PET findings for indeterminate bone lesions or lymph nodes were discussed at a multidisciplinary tumor board (MDT) in 2024–2025. An algorithm determining the level of suspicion for metastasis was developed in a multidisciplinary fashion, incorporating lesion location, conventional imaging features, PSMA-PET characteristics, and clinicopathological information. The application of the algorithm and outcomes were documented, compared against a composite reference standard. Comparisons were made with PSMA-RADS and PROMISE V2 PSMA-expression scores. 81 patients (median age 68, interquartile range 64–75) were included. Algorithm results were benign (48.1

Primary liver and biliary tract cancers remain major causes of global cancer mortality, with liver and intrahepatic bile duct cancers accounting for 866,136 new cases and 758,725 deaths worldwide in 2022. Curative surgery, transplantation, ablation, embolotherapy, and systemic therapy have improved outcomes, but many patients remain limited by cirrhosis, liver reserve, vascular invasion, biliary obstruction, anatomic constraints, or advanced presentation; population-level survival remains poor for both liver and bile duct cancers. Modern radiation therapy has emerged as an important local and regional modality for hepatocellular carcinoma, intrahepatic cholangiocarcinoma, extrahepatic cholangiocarcinoma, and gallbladder cancer.

PURPOSE:Stereotactic ablative body radiation therapy (SABR) is an emerging indication for localized renal cell carcinoma (RCC), yet there is a need for standardizing contouring practices, as accurate target delineation is essential to ensure optimal outcomes. Our objective was to develop consensus guidelines for target volume contouring for RCC SABR. METHODS AND MATERIALS:An international panel of RCC SABR experts affiliated with IROCK was convened. All were asked to contour target volumes for 4 relevant clinical scenarios: a large tumor (>10 cm) with inferior vena cava tumor thrombus; a central tumor abutting the renal hilum; a local recurrence following nephrectomy; and an ablation cavity recurrence after radiofrequency ablation. Participants also contoured 2 investigational renal substructures: renal cortex and renal hilum. Contours by case were analyzed using a Simultaneous Truth and Performance Level Estimation algorithm (95% CI). Consensus contours and guidelines statements were discussed and refined over 2 consensus meetings. Measures of variance and agreement, including dice similarity coefficients (DSCs), Mean Distance to Agreement, and Hausdorff Distance, were measured for each case. RESULTS:In total, 16 radiation oncologists participated. The median DSC was 0.85, and the median Mean Distance to Agreement/Hausdorff Distance were 2.17 mm/9.00 mm, respectively. The median DSC was greater than 0.70 for each case, suggesting "good agreement" among participants. Based on the consensus discussion, any tumor thrombus or ablation cavity should be included in the target volume; organ at risk dose constraints should take priority over target coverage in planning; and the ipsilateral renal cortex should be defined as the ipsilateral renal parenchyma, excluding the target volume, the renal pelvis, renal vasculature, and proximal ureter. CONCLUSIONS:We present the first international consensus contouring guideline for RCC SABR. There was strong agreement among experts, yielding high-fidelity consensus contours and guidance statements for each scenario. These results can be used as a guide for radiation oncologists interested in using SABR to treat patients with localized RCC.

Localized treatment of oligometastatic liver disease can improve both local control and survival. The liver is a frequent site of metastases from colorectal, breast, and lung cancers, but most patients are not eligible for surgical resection due to lesion number, location, or comorbidities. For these patients, non-surgical ablative methods such as radiofrequency ablation (RFA) and stereotactic body radiotherapy (SBRT) and increasingly microwave ablation (MWA) are used. RFA was used as the primary comparator in this review because it represents the most historically established and widely reported ablative modality in the comparative radiotherapy literature. While RFA has been the traditional approach, SBRT is emerging as a promising alternative, offering precise, non-invasive treatment. SBRT may be especially useful for larger lesions or tumors in locations where RFA is difficult to perform. However, high-quality evidence and large-scale trials are still needed to confirm its efficacy and define its role. This review compares the strengths and limitations of both methods and provides practical guidance for clinical decision-making in the treatment of patients with inoperable liver metastases.

e21503 Background: Mel-Bone represents a clinical challenge due to its known association with pain and pathological fractures. While bone metastases occur as frequently as brain metastases in stage IV melanoma (40-50% of cases), their clinicopathological and molecular characteristics remain largely understudied. Methods: We studied Mel-Bone patients treated at NYU Langone Health (2002-2023) and enrolled in a prospective biospecimen clinicopathological database. We examined the association between Mel-Bone characteristics (site, number, and radiological patterns) and overall survival (OS) using Kaplan-Meier and Cox regression. We also analyzed radiological changes of Mel-Bone over time in response to treatment. To better understand the molecular alterations associated with Mel-Bone progression, we compared RNAseq profiling of metastatic lymph nodes tissues (LNs) among 3 groups (progressed to the bone, to other distant sites, or did not progress to distant sites). We also performed Digital Spatial Profiling (DSP) on matched pairs of primary and Mel-Bone tissues. Differentially expressed genes were identified using a threshold of logFC > 0.5 and Benjamini-hochberg adjusted p-value < 0.05. Immunohistochemical (IHC) analysis of tissue microarrays (TMAs) generated from Mel-Bone and non-melanoma bone metastases tissues were examined to validate transcriptomic findings and identify Mel-Bone-specific features. Results: We identified 233 patients who developed Mel-Bone during active follow-up. 79/233 (37%) were symptomatic at presentation and 168 (73%) had multiple Mel-Bone. Imaging studies revealed that the majority of patients (77%) had osteolytic lesions, while 8% had osteosclerotic, and 15% had mixed lesions. Patients with Mel-Bone confined to the peripheral skeleton had significantly lower mortality risk (HR = 0.41, 95% CI: 0.26-0.66, p < 0.001) and higher rate of complete resolution on imaging post-treatment compared to those with axial or combined lesions (p < 0.01). Patients with a solitary bone lesion (27%) or isolated Mel-Bone with no extraosseous metastases (6.4%) had significantly improved OS (p < 0.0001 or p < 0.001, respectively). DSP revealed significant upregulation of vascular endothelial growth factor A (VEGFA) in Mel-bone tissues compared to their matched primary tissues (p < 0.0001). VEGFA was upregulated in LNs that metastasized to bone versus LNs that metastasized to other organs (p = 0.02). VEGFA was also overexpressed in Mel-Bone compared to non-melanoma Bone metastases (p < 0.001). Conclusions: Our data reveal distinct clinical and radiological features associated with diverse clinical courses of Mel-Bone that can impact patient prognosis and inform treatment strategies. The data also support a role of VEGFA upregulation in the progression of melanoma to bone. Mechanistic investigations are underway to determine the impact of inhibiting VEGFA on the course of Mel-Bone.

Pelvic nodal irradiation is often used for high-risk prostate adenocarcinoma. A commonly used alternative to low dose rate (LDR) brachytherapy, a 3-fraction SBRT boost with fiducial tracking may allow for better coverage of extracapsular extension and macroscopic seminal vesicle invasion. This study evaluates the practical impact of prior pelvic nodal irradiation on fiducial tracking during a subsequent 3-fraction robotic stereotactic body radiation therapy (SBRT) boost for high-risk prostate cancer and compares these outcomes to a cohort of patients undergoing definitive 5-fraction SBRT. In this institutional analysis, we prospectively collected fiducial tracking data for patients receiving a 3-fraction boost to the prostate and seminal vesicles after conventional nodal radiation. We also identified patients treated with 5-fraction SBRT with a low risk of nodal involvement. Monte Carlo estimates of the Fisher’s Exact Test assessed fiducial tracking loss. Continuous variables within the 5- and 3-fraction cohorts were compared using the Mann-Whitney Test. Changes in fiducial tracking and their association with pre-treatment factors were analyzed through the Kruskal-Wallis test and Monte Carlo for tracking patterns, and Spearman Correlation Coefficient and Mann-Whitney Test for deviations in tracking over 5 fractions. A total of 405 patients were treated from April 2021 to September 2023 with: (1) 5-fraction SBRT (n = 309, 76

Purpose While SABR is associated with excellent local control of primary renal cell carcinoma (RCC), outcomes based on clear cell RCC (ccRCC) and non-clear cell RCC (nccRCC) histologies are not well defined. This retropsective study's objective is to report the outcomes following SABR for uncommon subtypes of primary RCC. Methods and Materials Individual data of adult patients with biopsy-confirmed primary RCC receiving SABR between 2007 and 2021 from 16 institutions in Australia, Canada, Germany, Japan, and the USA were pooled. Patients with metastatic disease or upper tract urothelial carcinoma were excluded. The primary outcome was local failure (LF), based on the Response Evaluation Criteria in Solid Tumors version 1.1. Distant failure (DF), cancer-specific survival (CSS), treatment-related toxicity, and renal function changes following SABR were defined as secondary outcomes. Kaplan-Meier estimates were generated for LF, DF, and CSS stratified by ccRCC versus nccRCC histology, and compared using the log-rank test (for CSS) or Gray’s test (for LF and DF). Results Two hundred eleven patients with a biopsy-confirmed ccRCC (n = 167) or nccRCC (n = 44) were included. In the nccRCC group, 59% (n = 26/44) and 11% (n = 5/44) were papillary and chromophobe histologies, respectively. Patients with nccRCC were more likely to be older (median age at SABR, 77.2 years vs 71.5; p = .009) and to be treated with multifraction SABR (82% [n = 36/44] vs 38% [n = 63/167]; p < .001) than the ccRCC group. The median follow-up was 4.02 years (IQR, 3.43-4.94) and 4.25 years (IQR, 3.02-5.00) for the ccRCC and nccRCC groups, respectively. The 5-year cumulative incidence of LF was 1.5% (95% CI, 0.3%-4.8%) in the ccRCC group versus 2.4% (95% CI, 0.2%-11.0%) in the nccRCC group (hazard ratio [HR], 0.90; 95% CI, 0.10-8.31; p = .922). The corresponding cumulative incidence of DF at 5 years was 6.0% in the ccRCC group versus 2.9% in the nccRCC group (HR, 0.34; 95% CI, 0.04-2.68; p = .304). The 5-year estimated CSS was 96.4% in the ccRCC group versus 96.4% in the nccRCC group (HR, 2.04; p = .561). From baseline, the mean ± SD estimated glomerular filtration rate reduced by 11.4 ± 13.4 mL/min at 3 years and by 12.2 ± 14.0 mL/min at 5 years. Sixteen patients (7.6%) experienced grade 2 or higher toxicities, with grade 2 fatigue (5.7%) being the most common. Conclusions SABR provides excellent oncologic outcomes, irrespective of ccRCC or nccRCC histology.

Purpose: Since the inaugural workshop "Understanding High-Dose, Ultra-High Dose Rate and Spatially Fractionated Radiotherapy." hosted by the National Cancer Institute and sponsored by the Radiosurgery Society (RSS), growing collaborations and investigations have ensued among experts, practitioners, and researchers. The RSS GRID, LATTICE, Microbeam and FLASH (GLMF) Working Groups were formed as a framework for these efforts and have focused on advancing the understanding of the biology, technical/physical parameters, trial design, and clinical practice of these new radiation therapy modalities. Methods and Materials: In view of the steadily increasing clinical interest in Spatially Fractionated Radiotherapy (SFRT) and FLASH, a full-day symposium entitled "Advancements in GRID, LATTICE, and FLASH Radiotherapy Symposium" was established in 2022 that immediately preceded the RSS scientific meeting. This well-attended symposium focused on clinical, technical, and physics approaches for SFRT, and closely examining relevant radiobiological underpinnings. Practical clinical trial development was a highlighted discussion. An additional section reviewed proton therapy and other particle-based techniques for the delivery of GRID and LATTICE therapy. A treatment planning and delivery tutorial for GRID, LATTICE, and proton GRID/LATTICE was directed toward the real-world considerations for the development of new clinical GRID or LATTICE programs. An overall similar approach was applied to the discussion of FLASH. This report summarizes the content of the first GLMF Symposium and related work of the RSS GLMF Working Groups in the field of heterogeneous and ultrahigh dose rate irradiation, over approximately 2 years. Results: The GLMF Working Groups have continued to expand in membership and attendance, and several resultant trial concepts, research efforts, academic discussions, and peer-reviewed publications have followed as the number of institutions and practitioners using SFRT and FLASH continues to grow. Conclusions: The GLMF Working Groups and the RSS continue to demonstrate excellent progress in proliferating use of and improving understanding of SFRT and ultrahigh dose rate radiation therapy techniques. (c) 2024 American Society for Radiation Oncology. Published by Elsevier Inc. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

Background and objective: Renal function preservation is particularly important following nonoperative treatment of localized renal cell carcinoma (RCC) since patients are often older with medical comorbidities. Our objective was to report long-term renal function outcomes after stereotactic ablative radiotherapy (SABR) including patients with a solitary kidney. Methods: Patients with primary RCC treated with SABR with >= 2 yr of follow-up at 12 International Radiosurgery Consortium for Kidney institutions were included. Renal function was measured by estimated glomerular filtration rate (eGFR). Key findings and limitations: In total, 190 patients (56 with a solitary kidney) underwent SABR and were followed for a median of 5.0 yr (interquartile range [IQR]: 3.4- 6.8). In patients with a solitary kidney versus bilateral kidneys, pre-SABR eGFR (mean [standard deviation]) was 61.1 (23.2) versus 58.0 (22.3) ml/min (p = 0.32) and the median tumor size was 3.65 cm (IQR: 2.59-4.50 cm) versus 4.00 cm (IQR: 3.00-5.00 cm; p = 0.026). At 5 yr after SABR, eGFR decreased by -14.5 (7.6) and -13.3 (15.9) ml/min (p = 0.67), respectively, and there were similar rates of post-SABR dialysis (3.6% [n = 2/56] vs 3.7% [n = 5/134]). A multivariable analysis demonstrated that increasing tumor size (odds ratio [OR] per 1 cm: 1.57; 95% confidence interval [CI]: 1.14-2.16, p = 0.0055) and baseline eGFR (OR per 10 ml/min: 1.30; 95% CI: 1.02-1.66, p = 0.034) were associated with an eGFR decline of >= 15 ml/min at 1 yr. Conclusions and clinical implications: With long-term follow-up after SABR, kidney function decline remains moderate, with no observed difference between patients with a solitary kidney and bilateral kidneys. Tumor size and baseline eGFR are dominant factors predictive of long-term renal function decline. Patient summary: With long-term follow-up, stereotactic ablative radiotherapy (SABR) yields moderate long-term renal function decline and low dialysis rates even in patients with a solitary kidney. SABR thus represents a promising noninvasive, nephron-sparing option for patients with localized renal cell carcinoma. (c) 2024 Published by Elsevier B.V. on behalf of European Association of Urology.

Purpose Percentage of positive cores involved on a systemic prostate biopsy has been established as a risk factor for adverse oncologic outcomes and is a National Comprehensive Cancer Network (NCCN) independent parameter for unfavorable intermediate-risk disease. Most data from a radiation standpoint was published in an era of conventional fractionation. We explore whether the higher biological dose delivered with SBRT can mitigate this risk factor. Methods A large single institutional database was interrogated to identify all patients diagnosed with localized prostate cancer (PCa) treated with 5-fraction SBRT without ADT. Pathology results were reviewed to determine detailed core involvement as well as Gleason score (GS). High-volume biopsy core involvement was defined as ≥ 50%. Weighted Gleason core involvement was reviewed, giving higher weight to higher-grade cancer. The PSA kinetics and oncologic outcomes were analyzed for association with core involvement. Results From 2009 to 2018, 1590 patients were identified who underwent SBRT for localized PCa. High-volume core involvement was a relatively rare event observed in 19% of our cohort, which was observed more in patients with small prostates ( p < 0.0001) and/or intermediate-risk disease ( p = 0.005). Higher PSA nadir was observed in those patients with low-volume core involvement within the intermediate-risk cohort ( p = 0.004), which was confirmed when core involvement was analyzed as a continuous variable weighted by Gleason score ( p = 0.049). High-volume core involvement was not associated with biochemical progression ( p = 0.234). Conclusions With a median follow-up of over 4 years, biochemical progression was not associated with pretreatment high-volume core involvement for patients treated with 5-fraction SBRT alone. In the era of prostate SBRT and MRI-directed prostate biopsies, the use of high-volume core involvement as an independent predictor of unfavorable intermediate risk disease should be revisited.

A 64-year-old male smoker (0.25 packs per day for 40 years) with known chronic obstructive pulmonary disease (COPD) (forced expiratory volume < 1 L) undergoing surveillance imaging for multiple indeterminate lung nodules since 2019 was found to have a growing fludeoxyglucose-18 avid right posteromedial upper lobe spiculated nodule on imaging in 2022. He underwent computed tomography (CT)-guided biopsy demonstrating adenocarcinoma, epidermal growth factor receptor equivocal, anaplastic lymphoma kinase negative, programmed death ligand 1 of 5%, and next-generation sequencing negative for actionable mutations. Positron emission tomography CT showed 2 additional fludeoxyglucose-18 avid suspicious nodules: left anterior upper lobe and right posterolateral upper lobe. After multidisciplinary discussion, it was decided to treat the largest right posteromedial nodule first, assess response and adverse effects, and treat additional lesions as tolerated.

The use of radiation therapy (RT) for pancreatic cancer continues to be controversial, despite recent technical advances. Improvements in systemic control have created an evolving role for RT and the need for improved local tumor control, but currently, no standardized approach exists. Advances in stereotactic body RT, motion management, real-time image guidance, and adaptive therapy have renewed hopes of improved outcomes in this devastating disease with one of the lowest survival rates. This case-based guide provides a practical framework for delivering stereotactic body RT for locally advanced pancreatic cancer. In conjunction with multidisciplinary care, an intradisciplinary approach should guide treatment of the high-risk cases outlined within these guidelines for prospective peer review and treatment safety discussions.

BACKGROUND AND PURPOSE:Neoadjuvant stereotactic radiosurgery (NaSRS) is an emerging treatment option for brain metastases (BrM) planned for resection. The aim of this study was to report on the efficacy and safety of NaSRS in an individual patient data pooled analysis. MATERIALS AND METHODS:Patients undergoing single- and multi-fraction NaSRS for BrM at nine institutions in five countries (Australia, Canada, South Korea, Switzerland and USA) were included. Eligibility criteria included BrM from any primary malignancy and no prior local therapy. The primary endpoint was a composite of local recurrence (LR), any grade radionecrosis (RN), and/or nodular leptomeningeal disease (nLMD). Secondary endpoints included these endpoints and Grade ≥ 2 RN. Endpoints were evaluated using cumulative incidence functions. RESULTS:NaSRS was delivered to 179 patients with 189 BrM. Median follow-up was 28.4 months. Primary malignancies included non-small cell lung carcinoma (44 %) and melanoma (17 %). The median BrM diameter was 29 mm (IQR 21-36 mm). Single- and multi-fraction NaSRS was utilised in 100 (53 %) and 89 BrM (47 %) respectively. The median single-fraction dose was 18 Gy (IQR 16-20 Gy). Multi-fraction doses included 24 Gy in three fractions (55 %) and 27 Gy in three fractions (25 %). The 12-month incidence for the composite endpoint was 8.0 %. The 12-month incidence of LR was 4.6 %, any grade RN was 3.6 %, Grade ≥ 2 RN was 1.8 % and nLMD was 1.2 %. CONCLUSION:Neoadjuvant SRS results in favourable rates of LR, RN and nLMD. We provide a global experience of this treatment approach with long-term data and the largest cohort of patients undergoing multi-fraction SRS.

Purpose/Objective(s) Stereotactic ablative body radiotherapy (SABR) is an emerging treatment for patients with primary renal cell carcinoma (RCC), however variation in treatment protocols can exist between institutions. The goals of this study were to measure the variation in contouring RCC tumors for patients being treated with SABR and to develop consensus recommendations. Materials/Methods An international panel of 16 radiation oncologists was created from the IROCK meeting during ASTRO 2023. Four patient cases were: Case 1, a renal tumor greater than 10 cm in size with an IVC tumor thrombus; Case 2, a central renal tumor abutting the renal hilum; Case 3, a local recurrence of RCC post-nephrectomy; and Case 4, a residual tumor post-radiofrequency ablation (RFA). For each Case, panelists were asked for radiation planning details and to contour the target volumes on representative axial images using a computer-based training tool. Comparison of panelist contours with the were performed using the Dice-Similarity Coefficient (DSC), the Mean Distance to Agreement (MDA) and the Hausdorff Distance (HD). The DSC measures the overlap between two contours, so a higher DSC suggests greater agreement. The MDA and HD represent the mean and maximum distances between points on the two contours, so higher MDA and HD represent lower agreement. Consensus target volumes were derived using the STAPLE algorithm and discussed amongst the panel. Results Altogether, the panel included radiation oncologists from Canada, the USA, Australia, the Netherlands, and India. All panelists had previously treated at least 10 patients with SABR for primary RCC. Table 1 shows the DSC, MDA and HD for each case. Using an ANOVA analysis, for all Cases, the DSC, MDA and HD were not statistically different between participants (p = 0.32, p = 0.24, and p = 0.23, respectively). On qualitative inspection of participant contours, Case 4 showed the most agreement, followed by Case 3, Case 2, and then Case 1. Conclusion There was good agreement from our international expert panel on contouring renal tumors in all four Cases, with Case 4 having the greatest agreement, and Case 1 having the least agreement. Consensus recommendations based on this study may help improve the quality of SABR for RCC moving forward.

In the first analysis of its kind in the literature, we demonstrate that multifocal MRI-directed intraprostatic SBRT SIB yields no acute high-grade toxicity and is not associated with a higher risk of low-grade GU and GI toxicity relative to unifocal boost. Longer follow is necessary to determine risk of late toxicity and oncologic efficacy.

Purpose: Historically, toxicity concerns have existed in patients with large prostate glands treated with radiation therapy, particularly brachytherapy. There are questions whether this risk extends to stereotactic body radiation therapy (SBRT). In this retrospective review, we examine clinical outcomes of patients with prostate glands >= 100 cc treated curatively with SBRT. Methods and Materials: We retrospectively analyzed a large institutional database to identify patients with histologically con fi rmed localized prostate cancer in glands >= 100 cc, who were treated with de fi nitive-robotic SBRT. Prostate volume (PV) was determined by treatment planning magnetic resonance imaging. Toxicity was measured using Common Terminology Criteria for Adverse Events, version 5.0. Many patients received the Expanded Prostate Cancer Index Composite Quality of Life questionnaires. Minimum follow-up (FU) was 2 years. Results: Seventy-one patients were identi fi ed with PV >= 100 cc. Most had grade group (GG) 1 or 2 (41% and 37%, respectively) disease. All patients received a total dose of 3500 to 3625 cGy in 5 fractions. A minority (27%) received androgen deprivation therapy (ADT), which was used for gland size downsizing in only 10% of cases. Nearly half (45%) were taking GU medications for urinary dysfunction before RT. Median toxicity FU was 4.0 years. Two-year rates of grade 1+ genitourinary (GU), grade 1+ gastrointestinal (GI), and grade 2+ GU toxicity were 43.5%, 15.9%, and 30.4%, respectively. Total grade 3 GU toxicities were very limited (2.8%). There were no grade 3 GI toxicities. On logistic regression analysis, pretreatment use of GU medications was signi fi cantly associated with increased rate of grade 2+ GU toxicity (odds ratio, 3.19; P = .024). Furthermore, PV (analyzed as a continuous variable) did not have an effect on toxicity, quality of life, or oncologic outcomes. Conclusions: With early FU, ultra large prostate glands do not portend increased risk of high-grade toxicity after SBRT but likely carry an elevated risk of low-grade GU toxicity. (c) 2023 Published by Elsevier Inc. on behalf of American Society for Radiation Oncology.

There was no observed difference between renal function outcomes in patients with a solitary vs. bilateral kidneys. While larger tumor size may increase the risk of eGFR decline post-SABR, treatment of a solitary kidney does not appear to increase the risk of renal dysfunction long-term.

Background and purpose: Stereotactic radiosurgery (SRS) after maximal safe resection is an accepted treatment strategy for patients with cerebral metastatic disease. Despite its high conformality profile, the incidence of radionecrosis (RN) remains high. SRS delivered pre-operatively could be associated with a reduced incidence of RN. We sought to evaluate whether neoadjuvant SRS could reduce radiotherapy doses in a cohort of patients treated with post-operative SRS. Methods: A cohort of 47 brain metastases (BM) treated at 2 academic institutions was retrospectively analyzed. Subjects underwent surgical extirpation of BMs and subsequent SRS to surgical bed. Postoperative volumetric and dosimetric data was collected from records or recreations of delivered plans; pre-operative data were derived from hypothetical radiotherapy courses and compared using Wilcoxon signed-rank tests. Results: Higher planned tumor volume post-operatively (median[IQR] 12.28 [6.54, 18.69]cc vs 10.20 [4.53, 21.70]cc respectively, p = 0.4150) was observed. The median prescribed radiotherapy dose (DRx) was 16 Gy pre-operatively and 24 Gy post-operatively (p < 0.0001). Further investigations revealed improved pre-operative conformity index (1.23[1.20, 1.29] vs 1.29[1.23, 1.39], p = 0.0098) and gradient index (2.72[2.59, 2.98] vs 2.94[2.69, 3.47], p = 0.0004). A significant difference was found in normal brain tissue exposed to 10 Gy (12.97[6.78, 25.54]cc vs 32.13[19.42, 48.40]cc, p < 0.0001), 12 Gy (9.31[4.56, 17.43]cc vs 23.80[14.74, 36.56]cc, p < 0.0001), and 14 Gy (5.62[3.23, 11.61]cc vs 17.47[9.00, 28.31]cc, p < 0.0001), favoring pre-operative SRS. Conclusions: Neoadjuvant SRS is associated reduced DRx, better conformality profile and decreased radiation to normal tissue. These findings could support the use of neoadjuvant SRS for the treatment of BMs. (c) 2022 Published by Elsevier B.V. Radiotherapy and Oncology 184 (2023) 1-5