It has been shown that magnetic resonance imaging (MRI) guidance versus computed tomography (CT) guidance for aggressive margin-reduction (AMR) for stereotactic body radiotherapy (SBRT) in prostate cancer reduces acute toxicity, but the longer-term benefits are unknown. We performed a secondary analysis of MIRAGE, a phase 3 randomized clinical trial of MRI-guided SBRT for prostate cancer, to determine whether AMR with MRI guidance significantly reduced 2-yr physician-scored or patient-reported toxic effects in comparison to CT guidance. The cumulative incidence of 2-yr physician-scored toxicity, defined as grade >= 2 genitourinary (GU) and gastrointestinal (GI) toxic effects according to Common Terminology Criteria for Adverse Events v4.03, were lower with MRI guidance. Cumulative incidence rates of late grade >= 2 toxicity at 2 yr with MRI-guided versus CT-guided SBRT were 27% (95% confidence interval [CI] 19-39%)] versus 51% (95% CI 41-63%) for GU toxicity (p = 0.004), and 1.4% (95% CI 0.2-9.6) versus 9.5% (95% CI 4.6-19) for GI toxicity (p = 0.025). Cumulative logistic regression revealed that MRI-guided SBRT was associated with significantly lower odds of a clinically relevant deterioration in bowel function according to the Expanded Prostate Cancer Index Composite-26 score (odds ratio 0.444, 95% CI 0.209-0.942; p = 0.035) and in the Sexual Health Inventory in Men score (odds ratio 0.366, 95% CI 0.148-0.906; p = 0.03). There were no significant differences in the odds of a deterioration for other quality-of-life metrics. These findings support the hypothesis that aggressive planning for margin reduction for prostate SBRT using MRI leads to continued reductions in toxic effects over 2-yr follow-up. This trial is registered on ClinicalTrials.gov Identifier as NCT04384770. (c) 2024 The Authors. Published by Elsevier B.V. on behalf of European Association of Urology. This is an open access article under the CC BY license (http://creativecommons. org/licenses/by/4.0/).

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported. NRG Oncology RTOG 0415 is a randomized phase III noninferiority (NI) clinical trial comparing conventional fractionation (73.8 Gy in 41 fractions) radiotherapy (C-RT) with hypofractionation (H-RT; 70 Gy in 28) in patients with low-risk prostate cancer. The study included 1,092 protocol-eligible patients initially reported in 2016 with a median follow-up of 5.8 years. Updated results with median follow-up of 12.8 years are now presented. The estimated 12-year disease-free survival (DFS) is 56.1% (95% CI, 51.5 to 60.5) for C-RT and 61.8% (95% CI, 57.2 to 66.0) for H-RT. The DFS hazard ratio (H-RT/C-RT) is 0.85 (95% CI, 0.71 to 1.03), confirming NI ( P < .001). Twelve-year cumulative incidence of biochemical failure (BF) was 17.0% (95% CI, 13.8 to 20.5) for C-RT and 9.9% (95% CI, 7.5 to 12.6) for H-RT. The HR (H-RT/C-RT) comparing biochemical recurrence between the two arms was 0.55 (95% CI, 0.39 to 0.78). Late grade ≥3 GI adverse event (AE) incidence is 3.2% (C-RT) versus 4.4% (H-RT), with relative risk (RR) for H-RT versus C-RT 1.39 (95% CI, 0.75 to 2.55). Late grade ≥3 genitourinary (GU) AE incidence is 3.4% (C-RT) versus 4.2% (H-RT), RR 1.26 (95% CI, 0.69 to 2.30). Long-term DFS is noninferior with H-RT compared with C-RT. BF is less with H-RT. No significant differences in late grade ≥3 GI/GU AEs were observed between assignments (ClinicalTrials.gov identifier: NCT00331773 ).

Background:Lung computed tomography (CT) scan image registration isbeing used for lung function analysis such as ventilation.Given the high sensitiv-ity of functional analyses to image registration errors,an image registration errorscoring tool that can measure submillimeter image registration errors is needed. Purpose:To propose an image registration error scoring tool, termed lambda, whosespatial sensitivity can be used to quantify image registration errors in steepimage gradient regions under realistic noise conditions. Methods:lambda compares two images, termed reference and evaluated. The HUand distance scales of both images are normalized by user-selected scaling cri-teria.For each voxel in the reference image,the 4D Euclidian distances betweenthe reference voxel and the nearby evaluated voxels are calculated, and theminimum of these distances is lambda. We tested lambda in simulated individual bloodvessels comprised of 1, 3, and 5 mm diameter cylinders in 1x1x1mm3voxel images,which were blurred to simulate CT scanner intrinsic resolution andvolume averaging. We placed the simulated vessels in a homogeneous back-ground simulating parenchymal tissue density and injected 20, 40, and 60 HUstandard deviation Gaussian noise.We used isotropic Gaussian filters with 0.5,1.0, and 1.5 mm standard deviation kernels to smooth the simulated images.We assessed lambda using reference-evaluated vessel shifts of-1.0 to 1.0 mm in0.05 mm steps via rigid translational and rotational deformations. We exam-ined whether lambda tracked the translation vector via its internal spatial component.We restricted lambda to voxels using the angle, termed lambda, between the lambda vector andthe normalized spatial-distance axes, terming the results the restricted-lambda,lambda R,where lambda was hypothesized to be a proxy for image gradient. We determinedwhether lambda was coincident with the image gradient by examining if the voxels with|lambda|<= 30 degrees tracked the evaluated vessels. We used the 95thpercentile of lambda(R), lambda(95)(R),to determine spatial sensitivity,which we took as a conservative estimate of reg-istration error,by fitting lambda(95)(R) to a modified absolute-value function for each testedrigid translation, noise level, smoothing kernel, and vessel radius combination.We demonstrated the use of lambda on a clinical example consisting of a set of 25deformably registered free-breathing thoracic CT scans. We visually compared the lambda and lambda Rresults against the HU differences between each clinical image pair. Results:We found theta to be coincident with the image gradient.We found that lambda'sspatial component tracked the vessel shifts.We determined the spatial sensitiv-ity limit of lambda(95)(R) to be<0.2 mm.The noise level and smoothing kernel influenced lambda(95)(R) sensitivity, worsening with increasing noise, and improving with increasingsmoothing. For the clinical images, we observed lambda to qualitatively match the absolute difference of intensity in the image pairs and lambda(R) to restrict itself tohigh gradient regions or regions of visually apparent errors. Conclusion: lambda(95)(R) detected sub-millimeter positioning errors between simulatedvessels in the presence of typical CT noise. The noise magnitude and choiceof noise smoothing kernel were inversely related to lambda(95)(R) sensitivity,implying thatstudy-specific tuning of the pre-smoothing kernel may be required.The demon-strated ability in geometric tests of lambda(95)(R) to detect subvoxel DIR errors warrantsfurther evaluation and testing

Purpose/Objective(s) A recent phase III clinical trial at a single institute has demonstrated that aggressive margin reduction with MRI-guided prostate SBRT decreased acute grade ≥ 2 genitourinary (GU) and gastrointestinal (GI) toxicity following prostate SBRT, as compared against CT-guidance. We hypothesized that toxicity reduction could be attributable to decreased radiation exposure to nearby urinary and bowel structures. Herein, we evaluate the dosimetric impact of margin reduction on relevant GU and GI organs-at-risk (OARs) and its association with GU and GI toxicity. Materials/Methods One-hundred-and-fifty-six patients were randomized to CT-guided (4 mm PTV-expansion) or MR-guided (2 mm PTV-expansion) prostate SBRT (40 Gy in 5 fractions). Dosimetric statistics (D0.035cc, V40Gy, V39Gy, V20Gy) for relevant OARs (bladder, rectum, and small bowel) were calculated on pre-treatment simulation images. Physician-scored acute (0-3 months) and late (>3-24 months) GU and GI toxicity (CTCAE v4.03 scale) were evaluated. Statistical significance was assessed using two-sided, unpaired t-tests with level of significance set at 0.05. Results High dose radiation to the bladder was significantly decreased with MRI-guided treatment compared to CT-guided treatment (D0.035cc, V40Gy and V39Gy, p < 0.05). Rectal dosimetry was comparable between treatments regardless of hydrogel placement. Radiation to the small bowel (D0.035cc) trended lower in the MRI-guided treatment arm, but differences did not reach statistical significance. Regardless of treatment arm, bladder dose was higher in patients with acute (V20Gy, V39Gy, V40Gy, p<0.05) and late (V40Gy, p<0.05) grade ≥ 2 GU toxicity. Rectal dose trended higher in patients with acute and late grade ≥ 2 GI toxicity but failed to reach statistical significance. Small bowel dose was higher in patients with acute grade ≥ 2 GI toxicity (D0.035cc and V20Gy, p<0.05) and trended higher in those with late grade ≥ 2 GI toxicity. Conclusion Aggressive margin reduction results in significantly lower dose to the bladder, and regardless of margin, higher bladder doses were associated with acute and late toxicity. A similar, though less marked, association was seen for small bowel dosimetry. In contrast, rectal dosimetry was not significantly different between arms, though increased rectal dose trended towards association with acute and late toxicity. These results suggest that while margin reduction might explain the significant differences in GU toxicity, dosimetry alone may not account for the large differences seen in GI toxicity. Limitations include analysis of discrete dosimetric parameters and planned dose.

Purpose/Objective(s) Prospective data demonstrate that non-ablative stereotactic body radiation therapy (SBRT) for pancreas cancer is well tolerated and results in stable patient-reported quality of life (QOL) although few studies have evaluated long-term QOL beyond ∼3 months after SBRT. Ablative SBRT (BED10 ∼100 Gy) is increasingly being adopted and its effects on QOL are unknown. We now present QOL outcomes from a phase 2 trial evaluating ablative 5-fraction stereotactic MR-guided on-table adaptive radiation therapy (SMART) for borderline resectable and locally advanced pancreas cancer. Materials/Methods The multi-center single-arm phase 2 SMART trial enrolled 136 patients from January 2019 to January 2022 who received ≥3 months of induction chemotherapy without disease progression and were treated on a 0.35T MR-guided device with a prescribed dose of 50 Gy in 5 fractions (BED10 = 100 Gy). Intrafraction cine-MRI, soft tissue tracking, and automatic beam gating were mandatory. On-table adaptive replanning using an isotoxicity approach was performed prior to each fraction as needed. A secondary study endpoint was QOL using the NCCN-FACT FHSI-18 survey instrument at 3 times (T): prior to SMART (T1), 3 months after SMART (T2), and 12 months after SMART (T3). The total FHSI-18 score was calculated as a sum of the following subscale scores: disease related symptoms-physical, disease related symptoms-emotional, treatment side effects, and function/well-being. Results Surgery was performed in 44 patients (32.4%) after SMART. QOL assessment was completed at T1, T2, and T3 by 133 (97.8%) and 106 (77.9%), and 55 (40.4%) patients, respectively. Mean total score and subscale scores remained stable from T1-T2 or T1-T3. Mean individual question scores were stable from T1-T2 except for general pain (0.8 vs. 1.1; p=0.002) and localized stomach pain (1.0 vs. 1.3; p=0.013); a significant increase in pain scores was present among patients who had surgery after SMART while pain scores did not increase among those who did not have surgery. Mean individual scores were stable from T1-T3 except for increased stomach area pain (p<0.001) regardless of surgery and scores for feeling ill increased among patients who did not have surgery (p=0.004). Conclusion This is the first prospective evaluation of QOL after ablative radiation therapy for pancreas cancer demonstrating that overall QOL remains stable at 3 and 12 months after SMART. Additional analysis is warranted to clarify factors significantly associated with QOL including disease progression and additional therapy after SMART.

Purpose: Recently, a randomized trial demonstrated that a hyaluronic acid (HA) spacer placed before prostate hypofractionated intensity modulated radiation therapy improved rectal dosimetry and reduced acute grade 2+ gastrointestinal toxicity. However, 26.5% of patients receiving the spacer experienced a minimal clinically important decline (MCID) in bowel quality -of -life (QOL). The purpose of this study is to evaluate whether certain characteristics of the rectal spacer, as determined on postimplant imaging, were associated with change in bowel QOL at 3 -months. Methods and Materials: This is a secondary analysis of the 136 patients who received the HA spacer on the randomized trial. Postimplant spacer characteristics (ie, prostate -rectum spacing at superior/midgland/inferior/apex planes, symmetry, prostate volume, spacer volume) were systematically analyzed from structure sets using custom software code. Characteristics demonstrating signi fi cant associations with rectal V30 on multivariate linear regression were identi fi ed. Linear regression models were used to analyze the associations of such characteristics with change (baseline to 3 months) in both bowel and urinary QOL. Results: Apical spacing (mean 9.4 (standard deviation 4.0)) was signi fi cantly smaller than spacing measurements at more superior planes. 95.6% of patients had a symmetrical implant. Apical spacing ( P < .001) and prostate volume ( P = .01) were signi fi cantly associated with rectal V30 on multivariate analysis. However, only apical spacing (0.38/mm; P = .01) was associated with change in bowel QOL, even with adjustment of baseline bowel score (-0.33; P < .01). Percentages of patients with bowel MCID were 14.8% for > = 10 mm versus 36.6% for < 10 mm apical spacing ( P = .01). Apical spacing was not associated with change in urinary QOL (-0.09; P = .72), when adjusted for baseline urinary QOL (-0.52; P < .01). Conclusions: Greater apical spacing was associated with improved rectal dosimetry and smaller decline in bowel QOL at 3 -months. Further prospective data are needed to fully understand the rami fi cations of increased apical spacing. (c) 2023 The Author(s). Published by Elsevier Inc. on behalf of American Society for Radiation Oncology. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

Purpose/Objective(s) To conduct a deep-dive into the performance of the 5DCT breathing motion model from a clinical dataset Materials/Methods The 5DCT free-breathing CT simulation technique has been conducted on 295 patients. In a recent summary of the clinical 5DCT utilization, it was shown that 80% of the acquired 5DCT simulations were used for treatment planning. Some of the 20% of those unused simulations failed during part of their processing. 34 patients from the whole dataset were selected for in-depth analysis, including those with regular and irregular breathing. The scans were processed using a workflow that analyzes the 25 free-breathing CT scans and simultaneous surrogate, a sealed hollow accordion-shaped bellows wrapped around the abdomen. The workflow a) Analyzed the surrogate using the imaged diaphragm dome to calibrate the surrogate in terms of diaphragm position and speed b) Conducted deformable image registration using the current version of DEEDS, c) and fit the 5D motion model to each lung voxel. The calibrated breathing waveforms were analyzed to determine the overall breathing amplitudes, the breath-to-breath breathing amplitudes, and breathing irregularity (defined as the ratio of the standard deviation of breath-to-breath breathing amplitudes to the mean amplitude), breathing rate variation, and the lung-specific motion model root-mean squared (RMS) error residuals. Each lung voxel had an independent model residual measurement and the mean and 90th percentile errors were investigated, as well as the relative model errors by dividing the RMS model residual by the craniocaudal voxel motion and limiting the reported relative errors to voxels that moved more than 7.5 mm. Results The mean breathing amplitude and irregularity were 22.5 mm ± 7.7 mm (12.7 mm-42.4 mm) and 0.2 ± 0.12 (0.05 - 0.44, lower corresponding to more regular), respectively. The average period was 5.9 s ± 1.4 s (4.0 s-10.9 s) and irregularity of 0.26 ± 0.09 (0.10 - 0.41). The median RMS motion model residual error was 1.2 mm ± 0.5 mm (0.5 mm - 2.4 mm) and the worst 90th percentile by volume RMS error was 1.8 mm ± 0.7 mm (0.9 mm - 3.8mm). The 90th percentile relative model errors were 15.0% ± 4.0% (0.1% - 23.9%). The 90th percentile RMS was correlated against the breathing period and breathing amplitude irregularity, with correlation coefficients of 0.41 (P = 0.015) and 0.69 (P<0.01), respectively. Conclusion The 5DCT relative and absolute errors were relatively small but were well correlated with breathing period and amplitude irregularity. The correlation between model error and breathing irregularity were unsurprising and indicate that the motion model has room for improvement. Additionally, some of the worst performing regions were near the heart due to the uncorrelated cardiac motion, and the addition of an ECG could aid in those regions. We will expand this deep dive to all 295 patients and add tumor-specific statistics to determine the overall failure rate and attempt to create the next-generation motion model.

Importance Intrathoracic progression remains the predominant pattern of failure in patients treated with concurrent chemoradiation followed by a consolidation immune checkpoint inhibitor for locally advanced, unresectable non-small cell lung cancer (NSCLC).Objective To determine the maximum tolerated dose (MTD) and use of hypofractionated concurrent chemoradiation with an adaptive stereotactic ablative radiotherapy (SABR) boost.Design, Setting, and Participants This was an early-phase, single-institution, radiation dose-escalation nonrandomized controlled trial with concurrent chemotherapy among patients with clinical stage II (inoperable/patient refusal of surgery) or III NSCLC (American Joint Committee on Cancer Staging Manual, seventh edition). Patients were enrolled and treated from May 2011 to May 2018, with a median patient follow-up of 18.2 months. Patients advanced to a higher SABR boost dose if dose-limiting toxic effects (any grade 3 or higher pulmonary, gastrointestinal, or cardiac toxic effects, or any nonhematologic grade 4 or higher toxic effects) occurred in fewer than 33% of the boost cohort within 90 days of follow-up. The current analyses were conducted from January to September 2023.Intervention All patients first received 4 Gy x 10 fractions followed by an adaptive SABR boost to residual metabolically active disease, consisting of an additional 25 Gy (low, 5 Gy x 5 fractions), 30 Gy (intermediate, 6 Gy x 5 fractions), or 35 Gy (high, 7 Gy x 5 fractions) with concurrent weekly carboplatin/paclitaxel.Main Outcome and Measure The primary outcome was to determine the MTD.Results Data from 28 patients (median [range] age, 70 [51-88] years; 16 [57%] male; 24 [86%] with stage III disease) enrolled across the low- (n = 10), intermediate- (n = 9), and high- (n = 9) dose cohorts were evaluated. The protocol-specified MTD was not exceeded. The incidences of nonhematologic acute and late (>90 days) grade 3 or higher toxic effects were 11% and 7%, respectively. No grade 3 toxic effects were observed in the intermediate-dose boost cohort. Two deaths occurred in the high-dose cohort. Two-year local control was 74.1%, 85.7%, and 100.0% for the low-, intermediate-, and high-dose cohorts, respectively. Two-year overall survival was 30.0%, 76.2%, and 55.6% for the low-, intermediate-, and high-dose cohorts, respectively.Conclusions and Relevance This early-phase, dose-escalation nonrandomized controlled trial showed that concurrent chemoradiation with an adaptive SABR boost to 70 Gy in 15 fractions with concurrent chemotherapy is a safe and effective regimen for patients with locally advanced, unresectable NSCLC.

Background: The proximity of the rectum to the prostate in radiation therapy (RT) for prostate cancer presents a significant dosimetric challenge, leading to high rectal doses and resulting in detrimental side effects. Perirectal tissue spacing reduces rectal dose and gastrointestinal toxicities by mechanically separating these organs. A variety of materials have been explored for use as rectal spacers, most recently, a stabilized hyaluronic acid (HA) gel, which can be formed into deliberate a shape, and retains the definition of that shape, while remaining flexible, unlike polyethylene glycol (PEG) hydrogels. Purpose: This study evaluates the dosimetric impact of the spacer, including shape symmetry, the degree of separation at different locations, and the temporal stability of the space. Our goal is to provide physics-informed guidance on the optimal use of this sculptable spacer. Methods: A secondary analysis was performed on data from a 13-center prospective randomized trial (NCT 04189913), involving 136 patients with centrally-reviewed treatment plans conducted on CT/MR simulation scans before and after receiving HA spacer implants. Patients were treated with 60 Gy in 20 fractions to the prostate. For this study, python software was utilized for automated processing of DICOM RTstruct and RTdose files, facilitating detailed analysis of the spacer's impact on anatomical displacement and dosimetric outcomes. Complete dose-volume histograms (DVHs) were reconstructed, and combined into composite population DVHs before and after implant, verified against trial-reported dose points. Patients were divided into similar groups of separation and symmetry, and differences in their composite DVHs were tested for significance. Stability of the spacer was studied by comparing serial MRI images and by computing the distance between contours at four axial planes, at simulation and 3-month follow-up, post RT. Results: The introduction of the HA spacer significantly enhanced rectal sparing, as evidenced by a reduction in the mean rectal integral dose by over 6 Gy. High rates of implant symmetry (>95%) were observed, indicating nearly optimal lateral spacer placement. In superior-inferior coverage, this study like many others, saw the spacing largest at the superior extent but becoming more variable inferiorly at the level of the prostate apex. This allowed study of the apex as a specific area for dosimetric concern. Stability assessments confirmed that the spacer maintained its position and dimensions between the simulation and the 3-month post-RT, implying stable geometry during treatment, with only minimal separation changes observed. Statistical analysis using the Kruskal-Wallis test revealed significant correlations of larger separations at the inferior and apical planes with improved dosimetric outcomes, including rV30Gy. Conclusion: The use of a stabilized HA spacer in prostate RT effectively enhances prostate-rectum separation, leading to significant rectal sparing without undesirable dose compromises. This study underscores the role of strategic placement and shape, specifically including > 1 cm separation from the base down to the prostate apex. When combined with the treatment planning techniques used in the trial to create a steep dosimetric gradient across the spacer, these findings elucidate the dosimetric outcomes that can be expected in the clinical implementation of HA spacer. This is particularly relevant in the evolution of hypofractionated treatment regimens for prostate cancer therapy.

Objective. In image-guided radiotherapy (IGRT), off-by-one vertebral body misalignments are rare but potentially catastrophic. In this study, a novel detection method for such misalignments in IGRT was investigated using densely-connected convolutional networks (DenseNets) for applications towards real-time error prevention and retrospective error auditing. Approach. A total of 4213 images acquired from 527 radiotherapy patients aligned with planar kV or MV radiographs were used to develop and test error-detection software modules. Digitally reconstructed radiographs (DRRs) and setup images were retrieved and co-registered according to the clinically applied alignment contained in the DICOM REG files. A semi-automated algorithm was developed to simulate patient positioning errors on the anterior-posterior (AP) and lateral (LAT) images shifted by one vertebral body. A DenseNet architecture was designed to classify either AP images individually or AP and LAT image pairs. Receiver-operator characteristic curves (ROC) and areas under the curves (AUC) were computed to evaluate the classifiers on test subsets. Subsequently, the algorithm was applied to the entire dataset in order to retrospectively determine the absolute off-by-one vertebral body error rate for planar radiograph guided RT at our institution from 2011-2021. Main results. The AUCs for the kV models were 0.98 for unpaired AP and 0.99 for paired AP-LAT. The AUC for the MV AP model was 0.92. For a specificity of 95%, the paired kV model achieved a sensitivity of 99%. Application of the model to the entire dataset yielded a per-fraction off-by-one vertebral body error rate of 0.044% [0.0022%, 0.21%] for paired kV IGRT including one previously unreported error. Significance. Our error detection algorithm was successful in classifying vertebral body positioning errors with sufficient accuracy for retrospective quality control and real-time error prevention. The reported positioning error rate for planar radiograph IGRT is unique in being determined independently of an error reporting system.

Purpose/Objective(s) The MIRAGE trial (NCT 04384770) reported an acute toxicity benefit for patients with localized prostate cancer randomized to MRI-guided (MRgRT) compared with CT-guided (CTgRT) stereotactic body radiotherapy. This was attributed to PTV margin reduction from 4mm to 2mm enabled by improved soft tissue resolution during planning and real-time target motion tracking with MRgRT. However, there are clinical and planning limitations with MRgRT, and smaller CTgRT PTV margins may be feasible with triggered imaging and auto beam hold. We evaluated the dosimetric impact of reducing PTV margins in CTgRT compared with MRgRT patients in MIRAGE. Materials/Methods Sixteen CTgRT patients were retrospectively re-planned with 2mm and 3mm prostate PTV margins from 4mm per trial protocol. In patients receiving elective pelvic nodal irradiation (EPNI), nodal PTV margins were 4mm in both groups. We measured target, rectum, bladder, and small bowel dosimetric parameters and compared them in 16 similar MRgRT patients with Wilcoxon rank sum tests. Results In each group, 10 patients received 40 Gy in 5 fractions to the prostate only, and 6 patients received 25 Gy in 5 fractions EPNI with a simultaneous integrated boost (SIB) to 40 Gy to the prostate; 5 and 3 of these patients, respectively, received a SIB to 42 Gy gross prostate tumor. 7 and 9 patients had spacing gel and 2 and 1 patients had unilateral hip implants in the CTgRT and MRgRT arms, respectively. Dosimetric analysis is reported in the table. Conclusion Reducing prostate PTV margins from 4mm in CTgRT resulted in similar to superior target and organs-at-risk dosimetry compared with 2mm MRgRT prostate PTV margins, even with larger target volumes. Prospective evaluation is required to validate the safety and efficacy of prostate PTV margin reduction for patients undergoing CTgRT for localized prostate cancer.

Purpose Large-scale radiotherapy datasets drive predictive modeling, automated segmentation and planning, and personalized treatment, yet remain fragmented because treatment-planning (TPS) and record-and-verify (R&V) systems differ, DICOM implementations are inconsistent, and automated linkage tools are lacking. We developed a generalizable framework that automatically reconstructs complete planning and delivery datasets across diverse clinical environments with minimal manual effort. Methods We designed and implemented a software framework capable of automating the collection and integration of radiotherapy data from multiple institutions and TPS/R&V combinations. The system begins with Radiotherapy Treatment Records (RTRECORDS) and recursively traces unidirectional DICOM references to retrieve linked radiotherapy treatment plans (RTPLANs), doses (RTDOSEs), structure sets (RTSTRUCTs), planning images, image registrations (REG), and associated diagnostic images. Core components of the framework include automated DICOM queries, secure data transfer, integrity verification, linkage mapping, and detailed logging. To support diverse environments, we developed custom modules for non-DICOM-compliant systems, file format conversions, and robust error handling. Results The framework was deployed across four institutions using six different combinations of TPS and R&V systems. In a focused two-clinic implementation spanning 11 years of retrospective data, the system successfully processed and integrated data from 6,164 patients and 13,871 radiotherapy plans. The pipeline achieved a 99.76% success rate in identifying and linking complete treatment datasets, with an average processing time of 18 minutes per patient, demonstrating its efficiency and scalability in real-world conditions. Conclusion This automated framework provides a scalable and reliable solution for large-scale aggregation of radiotherapy data. It is compatible with heterogeneous clinical systems, including those lacking DICOM Query/Retrieve support, and overcomes key technical barriers to data integration. By enabling the creation of comprehensive, high-quality datasets, the framework supports advanced research and contributes to the improvement of clinical care in radiation oncology.

BACKGROUND:Misalignment to the incorrect vertebral body remains a rare but serious patient safety risk in image-guided radiotherapy (IGRT).PURPOSE:Our group has proposed that an automated image-review algorithm be inserted into the IGRT process as an interlock to detect off-by-one vertebral body errors. This study presents the development and multi-institutional validation of a convolutional neural network (CNN)-based approach for such an algorithm using patient image data from a planar stereoscopic x-ray IGRT system.METHODS:X-rays and digitally reconstructed radiographs (DRRs) were collected from 429 spine radiotherapy patients (1592 treatment fractions) treated at six institutions using a stereoscopic x-ray image guidance system. Clinically-applied, physician approved, alignments were used for true-negative, "no-error" cases. "Off-by-one vertebral body" errors were simulated by translating DRRs along the spinal column using a semi-automated method. A leave-one-institution-out approach was used to estimate model accuracy on data from unseen institutions as follows: All of the images from five of the institutions were used to train a CNN model from scratch using a fixed network architecture and hyper-parameters. The size of this training set ranged from 5700 to 9372 images, depending on exactly which five institutions were contributing data. The training set was randomized and split using a 75/25 split into the final training/ validation sets. X-ray/ DRR image pairs and the associated binary labels of "no-error" or "shift" were used as the model input. Model accuracy was evaluated using images from the sixth institution, which were left out of the training phase entirely. This test set ranged from 180 to 3852 images, again depending on which institution had been left out of the training phase. The trained model was used to classify the images from the test set as either "no-error" or "shifted", and the model predictions were compared to the ground truth labels to assess the model accuracy. This process was repeated until each institution's images had been used as the testing dataset.RESULTS:When the six models were used to classify unseen image pairs from the institution left out during training, the resulting receiver operating characteristic area under the curve values ranged from 0.976 to 0.998. With the specificity fixed at 99%, the corresponding sensitivities ranged from 61.9% to 99.2% (mean: 77.6%). With the specificity fixed at 95%, sensitivities ranged from 85.5% to 99.8% (mean: 92.9%).CONCLUSION:This study demonstrated the CNN-based vertebral body misalignment model is robust when applied to previously unseen test data from an outside institution, indicating that this proposed additional safeguard against misalignment is feasible.