External Beam Radiation Treatment Research Articles

Differences in real-world outcomes by risk classification for localized prostate cancer patients after radiation therapy.

Limited real-world evidence exists on the long-term clinical outcomes of patients with localized prostate cancer (LPC) who received external beam radiation therapy (EBRT) as the initial treatment. This study evaluated clinical outcomes of US patients with high-risk LPC (HR-LPC) and low/intermediate-risk LPC (LIR-LPC) who received EBRT. This retrospective study using Surveillance, Epidemiology, and End Results-Medicare linked data from 2012 to 2019 included patients ≥ 65 years old who received EBRT as initial therapy. Baseline patient characteristics were summarized, metastasis-free survival (MFS), overall survival, and time to initiation of advanced prostate cancer treatment were compared using Kaplan-Meier (KM) and adjusted Cox proportional hazard (PH) models. 5-year survival probabilities stratified by race/ethnicity (non-Hispanic [NH] White, NH Black, NH Asian, and Hispanic) were assessed. Of 11,313 eligible patients, 41% (n = 4600) had HR-LPC and 59% (n = 6713) had LIR-LPC. Patient characteristics for both groups were comparable, with mean age at EBRT initiation > 70 years, 86% white, and mean follow-up time >40 months. More patients in the HR-LPC than LIR-LPC groups (78% vs 34%) had concurrent androgen deprivation therapy use and for a longer duration (median 10.4 months vs. 7.4 months). A higher proportion of HR-LPC patients developed metastasis, died, or received advanced prostate cancer treatment. Adjusted Cox PH survival analyses showed significantly (p < 0.0001) higher risk of mortality (hazard ratios[HR], 1.57 [1.38, 2.34]), metastasis or death (HR, 1.97 [1.78, 2.17]), and advanced prostate cancer therapy use (HR, 2.57 [2.11, 3.14]) for HR-LPC than LIR-LPC patients. Within 5 years after the initial EBRT treatment, 18%-26% of patients with HR-LPC are expected to have died or developed metastasis. The 5-year MFS rate in the HR-LPC group was lower than the LIR-LPC group across all racial/ethnic subgroups. NH Black patients with HR-LPC had the highest all-cause mortality rate and lowest rate of receiving advanced prostate cancer treatment, compared to other racial/ethnic subgroups. This real-world study of clinical outcomes in patients with LPC treated with EBRT suggests substantial disease burden in patients with HR-LPC and highlights the need for additional treatment strategies to improve clinical outcomes in patients with HR-LPC.

Deep-Learning for Rapid Estimation of the Out-of-Field Dose in External Beam Photon Radiation Therapy – A Proof of Concept

Background and purpose: The dose deposited outside of the treatment field during external photon beam radiotherapy treatment, also known as out-of-field dose, is the subject of extensive study as it may be associated with a higher risk of developing a second cancer, and could have deleterious effects on the immune system which compromise the efficiency of combined radio-immunotherapy treatments. Out-of-field dose estimation tools developed today in research, including Monte Carlo simulations and analytical methods, are not suited to the requirements of clinical implementation because of their lack of versatility and their cumbersome application. We propose a proof of concept based on deep learning for out-of-field dose map estimation that addresses the above limitations.Materials and methods: For this purpose, a 3D U-Net, considering as inputs the in-field dose, as computed by the treatment planning system, and the patient's anatomy, was trained to predict out-of-field dose maps. The cohort used for learning and performance evaluation included 3151 pediatric patients from the [XXXX] database, treated in 5 clinical centers, whose whole-body dose maps were previously estimated with an empirical analytical method. The test set, composed of 433 patients, was split into 5 subdatasets, each containing patients treated with devices unseen during the training phase. Root mean square deviation (RMSD) evaluated only on non-zero voxels located in the out-of-field areas was computed as performance metric.Results: RMSD of 0.28 and 0.41 cGy.Gy−1 were obtained for the training and validation datasets, respectively. Values of 0.27, 0.26, 0.28, 0.30 and 0.45 cGy.Gy−1 were achieved for the 6 MV linac, 16 MV linac, Alcyon cobalt irradiator, Mobiletron cobalt irradiator, and betatron devices test sets, respectively.Conclusion: This proof-of-concept approach using a convolutional neural network has demonstrated unprecedented generalizability for this task, although it remains limited, and brings us closer to an implementation compatible with clinical routine.

Voxel-Level Dosimetry for Combined Iodine 131 Radiopharmaceutical Therapy and External Beam Radiation Therapy Treatment Paradigms for Head and Neck Cancer

PurposeTargeted radiopharmaceutical therapy (RPT) in combination with external beam radiotherapy (EBRT) shows promise as a method to increase tumor control and mitigate potential high-grade toxicities associated with re-treatment for patients with recurrent head and neck cancer. This work establishes a patient-specific dosimetry framework that combines Monte Carlo based dosimetry from the two radiation modalities at the voxel level using deformable image registration (DIR) and radiobiological constructs for patients enrolled in a phase I clinical trial combining EBRT and RPT. MethodsSerial SPECT/CT patient scans performed at approximately 24, 48, 72, and 168 hours post-injection of 577.2 MBq/m2 (15.6 mCi/m2) iodine-131 containing RPT agent called XXX 131. Clinical EBRT treatment plans were created on a treatment planning CT (TPCT) using RayStation; SPECT/CT images were deformably registered to the TPCT using the Elastix DIR module in 3D Slicer and assessed by measuring mean activity concentrations and absorbed doses. Monte Carlo EBRT dosimetry was computed using EGSnrc. RPT dosimetry was conducted using a GEANT4 based RPT dosimetry platform named XXX. Radiobiological metrics (BED, EQD2) were utilized to combine the two radiation modalities. ResultsThe DIR method provided good agreement for the activity concentrations and calculated absorbed dose in the tumor volumes for the SPECT/CT and TPCT; the maximum mean absorbed dose difference was -11.2%. Based on the RPT absorbed dose calculations, two to four EBRT fractions were removed from patients’ EBRT treatments. From the combined treatment, the absorbed dose to target volumes ranged from 57.14 – 75.02 Gy. When including partial volume corrections (PVC), the mean EQD2 to the PTV from EBRT+RPT was -3.11% to 1.40% different compared to EBRT alone. ConclusionThis work demonstrated the clinical feasibility of performing combined EBRT+RPT dosimetry on TPCTs. Dosimetry guides treatment decisions for EBRT and this work provides a bridge for the same paradigm to be implemented within the rapidly emerging clinical RPT space.

Developing a novel quasi-3D movable water phantom for radiation therapy workable in the magnetic resonance environment.

The use of magnetic resonance linear accelerators (MR-LINACs) for clinical treatment has opened up new possibilities and challenges in the field of radiation oncology. However, annual quality assurance (QA) is relatively understudied due to practical considerations. Thus, to overcome the difficulty of measuring the dose with a small water phantom for TRS-398 or TG-51 in all external beam radiation treatment unit environments, such as MR compatibility, we designed a remote phantom with a three-axis changeable capacity for QA. The designed water phantom was tested under an MR environment. The water phantom system comprised of three parts: a phantom box, a dose measurement tool, and a PMD401 drive system. The UNIDOSE universal dosimeter was used to collect beam data. The manufacturer's developer tools were utilized to position the measurement. To ensure magnetic field homogeneity, a distortion phantom was prepared using sixty fish oil capsules aligned radially to distinguish the oil and free air. The phantom was scanned in both the MR simulator and computed tomography (CT), and the acquired images were analyzed to determine the position shift. The dimensions of the device are 30 cm in the X-axis, 20 cm in the Y-axis, and 17 cm in the Z-axis. Total cost of materials was no more than $10,000 US dollars. Our results indicate that the device can function normally in a regular 1.5 T MR environment without interference from the magnetic field. The water phantom's traveling speed was found to be approximately 5 mm/s with a position difference confined within 6 cm intervals during normal use. The distortion test results showed that the prepared MR environment has uniform magnetic field homogeneity. In this study, we constructed a prototype water phantom device that can function in an MR simulator without interference between the magnetic field and electronic components. Compared to other commercially available MR-LINAC water phantoms, our device offers a more cost-effective solution for routine monthly QA. It can shorten the duration of QA tests and relieve the burden on medical physicists.

External beam radiotherapy in treatment of high-volume metastatic hormone-sensitive prostate cancer: clinical case

The standard treatment for metastatic hormone-sensitive prostate cancer does not include external beam radiotherapy (EBRT) and radionuclide therapy with radium-223.The article describes a clinical case of successful use of EBRT and radionuclide therapy with radium-223 in a patient with primary high-volume metastatic hormone-sensitive prostate cancer.The patient received diagnosis of prostate cancer сT3bN1M1b (Gleason score 8 (4 + 4)), stage IV (metastases in the bones, extraperitoneal and intrathoracic lymph nodes; prostate specific antigen (PSA) level was 4280 ng/mL). Between October of 2017 and January of 2018, the patient received 6 cycles of chemohormonal therapy (degarelix + docetaxel). Bilateral orchiectomy was performed on 05.02.2018, and the patient underwent palliative EBRT on cervical vertebrae between 04.10.2017 and 19.10.2017 with total dose of 32.6 Gy (equivalent to 38.5 Gy). The patient received systemic radiotherapy with one injection of samarium oxabifor (153Sm) 40 mCi (21.03.2018) and radium-223 (4 injections once a month (17.04.2018, 15.05.2018, 14.06.2018, 10.07.2018) + 2 injections 1 time per 3 months (October 2018, January 2019)). Partial response was achieved in the form of PSA decrease from 4280 ng/mL (September 2017) to 0.505 ng/mL (May 2019). Palliative EBRT for the prostate and pelvis was performed between 14.11.2018 and 19.12.2018 for total dose of 62.5 Gy (equivalent to 69 Gy). For 2 years remission was observed with PSA level of 0.3–0.5 ng/mL. In December of 2020, biochemical recurrence was diagnosed: PSA level increased from 0.61 ng/mL in October to 1.43 ng/mL on 28.12.2020. The second course of radionuclide therapy with radium-223 5,500 MBq/mL was performed (22.01.2021, 05.03.2021, 02.04.2021) with increase of PSA level to 1.92 ng/mL (May of 2021) and independent decrease to 0.542 ng/mL (June of 2022). In December of 2022, biochemical recurrence was observed with a small increase of PSA level to 1.67 ng/mL. Currently, the disease is stabilized.

PAEDIATRIC-15 MANAGEMENT OF PEDIATRIC CENTRAL NERVOUS SYSTEM TUMORS BY A NEURO-ONCOLOGY MULTIDISCIPLINARY TEAM : OUR EXPERIENCE

Abstract The outcome of pediatric central nervous system tumors has improved over the past decades due to advances in diagnostic testing, treatment and increased understanding of the disease biology. Nevertheless, the probability of survival of this tumors remains much lower in low-to middle-income countries. The gaps that prevent optimal clinical management of brain tumors are multifactorial and mostly related to underdiagnosis; a lack of specialized and dedicated radiologic, histopathologic, neurosurgical, radiotherapeutic, and oncology services, and a deficiency of coordinated multidisciplinary care in many centers. The aim of this report was to evaluate the impact of multidisciplinary team meetings on the clinical management of pediatric central nervous system tumors in Abidjan (Côte d'Ivoire). We retrospectively reviewed the clinical data of pediatric patients (aged &amp;lt;15 years) with central nervous system tumors diagnosed and treated in the Neurosurgery Department and National Center of Radiotherapy between 2019 (the year a neuro-oncological multidisciplinary staff was established) and 2023. Data on patient demographics, clinical notes, imaging studies, tumor characteristics and multidisciplinary team decision were collected from the multidisciplinary team database. During the multidisciplinary team meetings era, 40 pediatric central nervous system tumors were diagnosed and treated. The median age at diagnosis was 8.5 years. The mostly histological types were high grade and low grade gliomas. Decision-making was largely consistent with available guidelines. Therapeutic were surgery, external beam radiation treatment with concurrent and adjuvant chemotherapy. Benefits of neuro-oncology multidisciplinary team include coordination, direction for complicated cases, education, and a forum for communication, and clinical trials.

Predictive Value of Tumor Volume on Local Control in Hepatocellular Carcinoma Treated with Image Guided Hypofractionated Radiation Treatment

External beam radiation treatment (EBRT) is an important local treatment in liver-confined hepatocellular carcinoma (HCC) patients who are not candidates for curative therapy. EBRT dose, technique and prognostic factors are evolving. We hypothesized that tumor volume to liver volume ratio can be a predictor of local control (LC) in patients treated with hypo-fractionated radiation (HFRT) in HCC MATERIALS/METHODS: We retrospectively reviewed 50 patients of HCC treated with HFRT at our institution. HFRT schedule was chosen such that the radiation dose to the remaining liver and other organs at risk (OAR) met the standard dosimetric constraints. Image guided techniques were used for motion management, internal target volume (ITV) and planning target volume (PTV) delineation. Tumor to Liver Ratio (TLR) was defined as ratio of PTV volume to whole liver volume. TLR ≤ 0.3 was considered as low volume disease and TLR > 0.3 was considered as high-volume disease. The radiation dose ranged from 45 Gy to 67.5 Gy in 5 - 15 fractions. The biologically equivalent dose (BED) for tumor ranged from 58.5 Gy10 to 100 Gy10. Local control (LC) was evaluated by Kaplan-Meier analysis, with log-rank test for groups stratified as per TLR. Multivariate Cox regression analysis was performed to identify additional prognostic factors. The mean duration of follow-up was 24 months. The median age was 69 years (range 50 - 90) and 76% were males. 32 patients had CP-A class cirrhosis while 17 had CP-B and 1 had CP-C class. BCLC stage A, B, C and D was seen in 2, 14, 33 and 2 patients, respectively. Portal vein thrombosis was present in 9 patients and prior trans-arterial chemo embolization (TACE) was done in 23 patients. The median volume of PTV was 551 cc (range 52 - 1990 cc). The TLR ranged from 0.04 - 0.67 with a median of 0.29. The median BED radiation dose was 78.4 Gy10 (range - 58.5 Gy10 to 100 Gy10). Nine patients had local recurrence with overall LC rate of 82%. The LC was better in low volume tumors, with the TLR cut-off of 0.3 as a significant factor associated with LC (p = 0.007). The 1-year actuarial LC with TLR ≤ 0.3 was 88% as compared 61% in TLR of > 0.3 (p = 0.007). BED ≥60 Gy10 was associated with better 1 year LC as compared to BED < 60 Gy10 (89% vs 62%; p = 0.11). ALBI grade 1 was associated with better 1 year LC as compared to ALBI grade 2 (80% versus 75%; p = 0.40). On multivariate analysis, high volume disease and TLR >0.3 were significant prognostic factor for LC. HFRT has good 1-year local control of 82% in carefully selected unresectable HCC. Radiation with BED greater than 60 Gy10 and ALBI grade 1 showed a trend towards better LC. Smaller tumors had better LC with a PTV to liver ratio (TLR) of < 0.3. This information can help in identifying the poor responders, intensifying the radiation treatment and adding additional therapy to improve the oncological outcomes.

The Environmental Impact of Radiation Oncology: The "Footprint" of External Beam Radiation Therapy

There is a growing concern for the healthcare sector's impact on the environment. Prior carbon impact studies in radiation oncology have been limited in scope and methodology. This study aims to fill this gap by using an internationally recognized cradle-to-grave life cycle assessment (LCA) approach to quantify all environmental impacts from raw material extraction to product disposal for external beam radiation therapy (EBRT) in treating the most commonly diagnosed cancers. This LCA was performed in accordance with ISO 14040 and 14044 at a single academic medical center. It quantified the environmental impact of EBRT across four categories: global warming potential (GWP), carcinogenic and non-carcinogenic human toxicity, and respiratory effects (PM2.5), from initial consultation to the completion of the last EBRT fraction for each disease site. Data collection involved weighing all materials used, measuring/calculating building and equipment electricity usage (e.g., HVAC and Linacs), and recording patient and staff transit. The study analyzed the impact of both minimum and maximum fractionations for each disease site and simulated alternative clinical scenarios such as telemedicine, renewable energy use and hypofractionation. Regardless of disease site, there were significant differences in the environmental impacts associated with transit, electricity and supplies for EBRT treatment cycles. Staff and patient transport contributed the most, accounting for >92% of the total environmental impact including GWP (5.02x102 ± 9.38x101 kgCO2eq), carcinogenic (6.25x10-5 ± 1.23x10-5 CTUh) and non-carcinogenic human toxicity (1.16x10-4 ± 2.35x10-5 CTUh). Electricity accounted for 1-13% of the total impact, with most impact arising from respiratory effects (3.05x10-2 kg ± 2.72x10-3 PM2.5). The impact of supplies and materials was less than 3% across all categories. Alternative scenario modeling showed that telemedicine had a maximum impact reduction of 3.5% (2.54x 101kgCO2eq) for GWP, while renewable energy use had a maximum impact reduction of 8% (2.37 x 10-2 PM2.5) for respiratory effects. Reducing the number of total treatment days via hypofractionation can reduce GWP by 67-78% and carcinogenic emissions by 63-77% (3.48 x 102 - 5.53 x 102 kgCO2eq) and (3.73 x 10-5 - 6.85 x 10-5CTUh), respectively, with variation depending on the total number of fractions. This study provides a comprehensive environmental impact assessment for EBRT among the most commonly treated disease sites, establishing a baseline metric and identifying targets for impact reduction. We are currently performing a multi-center validation study to be completed by June 2023. Our findings fill an important gap in cancer care and are critical for developing sustainable practices in the face of increasing demand for radiotherapy in a changing climate. LCAs evaluating all aspects of cancer care will be essential for promoting equitable and sustainable care.

Evaluation of a Deep Learning-based Algorithm for Post-Radiotherapy Prostate Cancer Local Recurrence Detection Using Biparametric MRI

ObjectiveTo evaluate a biparametric MRI (bpMRI)-based artificial intelligence (AI) model for the detection of local prostate cancer (PCa) recurrence in patients with radiotherapy history. Materials and MethodsThis study included post-radiotherapy patients undergoing multiparametric MRI and subsequent MRI/US fusion-guided and/or systematic biopsy. Histopathology results were used as ground truth. The recurrent cancer detection sensitivity of a bpMRI-based AI model, which was developed on a large dataset to primarily identify lesions in treatment-naïve patients, was compared to a prospective radiologist assessment using the Wald test. Subanalysis was conducted on patients stratified by the treatment modality (external beam radiation treatment [EBRT] and brachytherapy) and the prostate volume quartiles. ResultsOf the 62 patients included (median age = 70 years; median PSA = 3.51 ng/ml; median prostate volume = 27.55 ml), 56 recurrent PCa foci were identified within 46 patients. The AI model detected 40 lesions in 35 patients. The AI model performance was lower than the prospective radiology interpretation (Rad) on a patient-(AI: 76.1% vs. Rad: 91.3%, p = 0.02) and lesion-level (AI: 71.4% vs. Rad: 87.5%, p = 0.01). The mean number of false positives per patient was 0.35 (range: 0–2). The AI model performance was higher in EBRT group both on patient-level (EBRT: 81.5% [22/27] vs. brachytherapy: 68.4% [13/19]) and lesion-level (EBRT: 79.4% [27/34] vs. brachytherapy: 59.1% [13/22]). In patients with gland volumes >34 ml (n = 25), detection sensitivities were 100% (11/11) and 94.1% (16/17) on patient- and lesion-level, respectively. ConclusionThe reported bpMRI-based AI model detected the majority of locally recurrent prostate cancer after radiotherapy. Further testing including external validation of this model is warranted prior to clinical implementation.

PRIMO Monte Carlo software as a tool for commissioning of an external beam radiotherapy treatment planning system.

The purpose was to validate the PRIMO Monte Carlo software to be used during the commissioning of a treatment planning system (TPS). The Acuros XB v. 16.1 algorithm of the Eclipse was configured for 6 MV and 6 MV flattening-filter-free (FFF) photon beams, from a TrueBeam linac equipped with a high-definition 120-leaf multileaf collimator (MLC). PRIMO v. 0.3.64.1814 software was used with the phase space files provided by Varian and benchmarked against the reference dosimetry dataset published by the Imaging and Radiation Oncology Core-Houston (IROC-H). Thirty Eclipse clinical intensity-modulated radiation therapy (IMRT)/volumetric modulated arc therapy (VMAT) plans were verified in three ways: 1) using the PTW Octavius 4D (O4D) system; 2) the Varian Portal Dosimetry system and 3) the PRIMO software. Clinical validation of PRIMO was completed by comparing the simulated dose distributions on the O4D phantom against dose measurements for these 30 clinical plans. Agreement evaluations were performed using a 3% global/2 mm gamma index analysis. PRIMO simulations agreed with the benchmark IROC-H data within 2.0% for both energies. Gamma passing rates (GPRs) from the 30 clinical plan verifications were (6 MV/6MV FFF): 99.4% ± 0.5%/99.9% ± 0.1%, 99.8% ± 0.4%/98.9% ± 1.4%, 99.7% ± 0.4%/99.7% ± 0.4%, for the 1), 2) and 3) verification methods, respectively. Agreement between PRIMO simulations on the O4D phantom and 3D dose measurements resulted in GPRs of 97.9% ± 2.4%/99.7% ± 0.4%. The PRIMO software is a valuable tool for dosimetric verification of clinical plans during the commissioning of the primary TPS.

Locoregional Treatment in Intrahepatic Cholangiocarcinoma: Which Treatment for Which Patient?

For unresectable intrahepatic cholangiocarcinoma (iCC), different locoregional treatments (LRT) could be proposed to patients, including radiofrequency ablation (RFA) and microwave ablation (MWA), external beam radiotherapy (EBRT) or transarterial treatments, depending on patient and tumor characteristics and local expertise. These different techniques of LRT have not been compared in a randomized clinical trial; most of the relevant studies are retrospective and not comparative. The aim of this narrative review is to help clinicians in their everyday practice discuss the pros and cons of each LRT, depending on the individual characteristics of their patients.

Comparison of salvage high dose-rate brachytherapy and external beam radiotherapy for treatment of prostate cancer local recurrence after radical prostatectomy

Aim. To compare clinical efficacy of salvage high dose-rate brachytherapy (HDR-BT) and external beam radiotherapy (EBR) in treatment of local recurrence of prostate cancer after radical prostatectomy (RP).Materials and methods. Between January 2017 and December 2020, 60 patients with local recurrence of prostate cancer after RP were treated at the Russian Scientific Center of Roentgenology and Radiology. Two groups were identified: group 1 included 30 patients who underwent salvage external beam radiation therapy (EBRT) according to the classical fractionation regimen; in group 2, within the framework of the scientific protocol, 30 patients underwent 2 fractions of salvage HDR-BT with single boost dose of 15 Gy for total boost dose of 30 Gy. All patients in group 2 underwent pelvic multiparametric magnetic resonance imaging and positron emission tomography-computed tomography with prostatespecific membrane antigen ligands. In the 2nd group, transrectal biopsy of the prostate bed was also performed. Overall and biochemical recurrence-free survival, as well as the profile of early and late radiation complications, were analyzed.Results. Mean age of the patients at the time of salvage radiation therapy was 67.5 years (95 % confidence interval 66.1–69). Median time before development of biochemical relapse after RP was 24 months (interquartile range 13–46 months). Median follow-up period for all patients was 45 months (interquartile range 36–63 months). There were no dropouts in this study. The overall survival rate was 100 % in both groups. Comparative analysis of prostate specific antigen (PSA)-specific recurrence-free survival showed a clear trend toward an increase in the brachytherapy group; however, with the number of observations, statistically significant differences could not be achieved (p = 0.075). Salvage EBRT is more toxic than salvage HDR-BT. Comparative assessment of radiation adverse effects revealed higher frequency of early genitourinary toxicity of grade I and intestinal toxicity of grades I and II in the salvage EBRT group than in the salvage brachytherapy group, as well as late gastrointestinal toxicity of grade I and II.Conclusion. Salvage HDR-BT with 15 Gy × 2 fractions with total boost dose of up to 30 Gy was proved to be a promising treatment for local recurrence of prostate cancer after RP with an acceptable toxicity profile. There was also a trend towards increased PSA-specific recurrence-free survival in the salvage brachytherapy group compared with the salvage EBRT group.

Clinical feasibility of a commercially available MRI-only method for radiotherapy treatment planning of the brain.

Advancements in deep-learning based synthetic computed tomography (sCT) image conversion methods have enabled the development of magnetic resonance imaging (MRI)-only based radiotherapy treatment planning (RTP) of the brain. This study evaluates the clinical feasibility of a commercial, deep-learning based MRI-only RTP method with respect to dose calculation and patient positioning verification performance in RTP of the brain. Clinical validation of dose calculation accuracy was performed by a retrospective evaluation for 25 glioma and 25 brain metastasis patients. Dosimetric and image quality of the studied MRI-only RTP method was evaluated by a direct comparison of the sCT-based and computed tomography (CT)-based external beam radiation therapy (EBRT) images and treatment plans. Patient positioning verification accuracy of sCT images was evaluated retrospectively for 10 glioma and 10 brain metastasis patients based on clinical cone-beam computed tomography (CBCT) imaging. An average mean dose difference of Dmean = 0.1% for planning target volume (PTV) and 0.6% for normal tissue (NT) structures were obtained for glioma patients. Respective results for brain metastasis patients were Dmean = 0.5% for PTVs and Dmean =1.0% for NTs. Global three-dimensional (3D) gamma pass rates using 2%/2 mm dose difference and distance-to-agreement (DTA) criterion were 98.0% for the glioma subgroup, and 95.2% for the brain metastasis subgroup using 1%/1 mm criterion. Mean distance differences of <1.0 mm were observed in all Cartesian directions between CT-based and sCT-based CBCT patient positioning in both subgroups. In terms of dose calculation and patient positioning accuracy, the studied MRI-only method demonstrated its clinical feasibility for RTP of the brain. The results encourage the use of the studied method as part of a routine clinical workflow.

Implementation of a knowledge-based decision support system for treatment plan auditing through automation.

Independent auditing is a necessary component of a comprehensive quality assurance (QA) program and can also be utilized for continuous quality improvement (QI) in various radiotherapy processes. Two senior physicists at our institution have been performing a time intensive manual audit of cross-campus treatment plans annually, with the aim of further standardizing our planning procedures, updating policies and guidelines, and providing training opportunities of all staff members. A knowledge-based automated anomaly-detection algorithm to provide decision support and strengthen our manual retrospective plan auditing process was developed. This standardized and improved the efficiency of the assessment of our external beam radiotherapy (EBRT) treatment planning across all eight campuses of our institution. A total of 843 external beam radiotherapy plans for 721 lung patients from January 2020 to March 2021 were automatically acquired from our clinical treatment planning and management systems. From each plan, 44 parameters were automatically extracted and pre-processed. A knowledge-based anomaly detection algorithm, namely, "isolation forest" (iForest), was then applied to the plan dataset. An anomaly score was determined for each plan using recursive partitioning mechanism. Top 20 plans ranked with the highest anomaly scores for each treatment technique (2D/3D/IMRT/VMAT/SBRT) including auto-populated parameters were used to guide the manual auditing process and validated by two plan auditors. The two auditors verified that 75.6% plans with the highest iForest anomaly scores have similar concerning qualities that may lead to actionable recommendations for our planning procedures and staff training materials. The time to audit a chart was approximately 20.8 min on average when done manually and 14.0 min when done with the iForest guidance. Approximately 6.8 min were saved per chart with the iForest method. For our typical internal audit review of 250 charts annually, the total time savings are approximately 30hr per year. iForest effectively detects anomalous plans and strengthens our cross-campus manual plan auditing procedure by adding decision support and further improve standardization. Due to the use of automation, this method was efficient and will be used to establish a standard plan auditing procedure, which could occur more frequently.

Recurrent Differentiated Thyroid Cancer: The Current Treatment Options.

Differentiated thyroid carcinomas (DTC) have an excellent prognosis, but this is sometimes overshadowed by tumor recurrences following initial treatment (approximately 15% of cases during follow-up), due to unrecognized disease extent at initial diagnosis or a more aggressive tumor biology, which are the usual risk factors. The possible sites of recurrence are local, regional, or distant. Local and regional recurrences can usually be successfully managed with surgery and radioiodine therapy, as are some isolated distant recurrences, such as bone metastases. If these treatments are not possible, other therapeutic options such as external beam radiation therapy or systemic treatments should be considered. Major advances in systemic treatments have led to improved progression-free survival in patients previously considered for palliative treatments; among these treatments, the most promising results have been achieved with tyrosine kinase inhibitors (TKI). This review attempts to give a comprehensive overview of the current treatment options suited for recurrences and the new treatments that are available in cases where salvage surgery is not possible or in cases resistant to radioiodine.

PO-2068 Errors detected during physics plan review for external beam radiotherapy treatment plans

PO-2068 Errors detected during physics plan review for external beam radiotherapy treatment plans

Abstract P1-10-06: Carcinoma en Cuirasse Secondary to Locally Advanced Breast Carcinoma: a case report

Abstract Introduction &amp; Objective This report highlights an unusual presentation of skin metastasis of inflammatory breast cancer that resembles a rare condition called Carcinoma en Cuirasse (CeC). CeC was first described by anatomist Alfred Velpeau in 1838 when he observed how the coalescing nodules and diffuse sclerodermoid induration found on the chest and abdomen in CeC resembled the medieval steel breastplate or a cuirasse. Case Presentation A 62-year-old female presented to the emergency department for evaluation of a palpable left breast mass and concurrent skin lesions for the past 5 months. Based on the erosion of the nipple, chest CT, as well as core needle and skin biopsy, a diagnosis of stage IV (cT4d, cN3, cM1) ER+, PR-, HER2/neu- advanced/inflammatory breast carcinoma was made. The patient underwent a 20-week course of neoadjuvant chemotherapy followed by 25 treatments of neoadjuvant external beam radiotherapy (EBRT) with a total dose of 5000cGy to the left breast and the regional lymph node due to disease progression after 4 cycles of neoadjuvant chemotherapy. She proceeded to bilateral modified radical mastectomy and bilateral lymph node involvement was found, and later disease progressed with skin involvement outside the EBRT treatment field. Additional 25 treatment of palliative radiotherapy was utilized with another 5000cGy, followed by 2 months of chemotherapy to provide better palliation and quality of life. Upon completion of therapy, a unique skin metastasis pattern was noticed. Shortly afterward the patient passed away from severe sepsis secondary to multiple wounds infected by drug-resistant Pseudomonas aeruginosa followed by Clostridium difficile colitis. Conclusion This case shows clinical characteristics of Carcinoma en Cuirasse and provides important considerations for more research to be done to highlight the unique pattern of skin metastasis following radiation and the potential use for radiation to treat chemotherapy-resistant skin metastasis from recurrent invasive breast carcinoma. Citation Format: Chung-Tang Liu, Keri Lanier. Carcinoma en Cuirasse Secondary to Locally Advanced Breast Carcinoma: a case report [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P1-10-06.

Salvage Perioperative Interstitial High-Dose-Rate Interventional Radiotherapy (Brachytherapy) for Local Recurrences of the Chest Wall Following Mastectomy and Previous External Irradiation.

(1) Background: To investigate the technical feasibility, safety, and efficacy of interstitial perioperative high-dose-rate interventional radiotherapy (HDR-IRT, brachytherapy) as a local salvage treatment combined with surgery for local chest wall recurrences following mastectomy and subsequent external beam radiation treatment (EBRT). (2) Methods: A retrospective analysis of 56 patients treated with interstitial HDR-IRT in combination with local surgery of a chest wall recurrence of breast cancer after previous treatment with mastectomy and EBRT from 2008 to 2020. (3) Results: Local recurrence following HDR-IRT was encountered in seven (12.5%) patients. The 1-year local recurrence-free survival (RFS), 3-year RFS, and 5-year RFS were 91%, 82%, and 82%, respectively. The 1-year overall survival (OS), 3-year OS, and 5-year OS was 85.5%, 58%, and 30%, respectively. Acute grade 1-2 radiation dermatitis was observed in 22 (39.3%) patients. Late ≥grade 3 toxicities were encountered in five (8.9%) patients. (4) Conclusions: Salvage perioperative interstitial high-dose-rate interventional radiotherapy (brachytherapy) combined with surgery seems to be an effective interdisciplinary management with acceptable treatment-related toxicity for local recurrences of the chest wall following mastectomy and previous external irradiation.

Reviewing Stereotactic Body Radiation Therapy Boost after Neoadjuvant Chemoradiation as an Alternative to Brachytherapy Boost for Locally Advanced Cervical Cancer

It is generally agreed upon that concurrent chemoradiotherapy (CCRT) is the treatment of choice for locally advanced cervical cancer (LACC). Radiotherapy consists of pelvic external beam radiation therapy (EBRT) and intracavitary brachytherapy (BT) to boost the cervix with coexisting residual tumors. Both of these treatments are administered simultaneously. In developing countries, however, there is a trend toward favoring surgery over other sorts of therapy. This preference can be attributed to several factors, including the fact that surgery is more readily available, socially acceptable, and culturally understood. On the other hand, with the development of more advanced techniques for external beam radiation treatment (EBRT), the usage of brachytherapy (BT), which is intended to boost the cervix in patients diagnosed with cervical cancer (CC), has been steadily decreasing in industrialized countries. The manner in which LACC has been treated as of late has become a contentious issue. In women who have locally advanced CC, we do not have any prospective evidence to support the idea that surgery or current EBRT, or stereotactic body radiation therapy (SBRT), may be substituted for intracavitary BT boost as a treatment option. This study aims to review SBRT as an alternative to brachytherapy following neoadjuvant concurrent chemotherapy and radiation therapy.

Determining Combined Modality Dosimetric Constraints by Integration of IMRT and LDR Prostate Brachytherapy Dosimetry and Correlation with Toxicity

Intermediate- and high-risk prostate cancer patients undergoing combination external beam radiation therapy (EBRT) and low dose rate (LDR) brachytherapy have demonstrated increased genitourinary (GU) toxicity. We have previously demonstrated a method to combine EBRT and LDR dosimetry. In this work, we use this technique for a sample of patients with intermediate- and high-risk prostate cancer, correlate with clinical toxicity, and suggest preliminary summed organ-at-risk constraints for future investigation. Intensity modulated EBRT and 103Pd-based LDR treatment plans were combined for 138 patients using biological effective dose (BED) and deformable image registration. GU and gastrointestinal (GI) toxicity were compared with combined dosimetry for the urethra, bladder, and rectum. Differences between doses in each toxicity grade were assessed by analysis of variance (α=0.05). Combined dosimetric constraints are proposed using the mean organ-at-risk dose, subtracting 1 standard deviation for a conservative recommendation. The majority of our 138-patient cohort experienced grade 0 to 2 GU or GI toxicity. Six grade 3 toxicities were noted. Mean prostate BED D90 (± 1 standard deviation) was 165.5±11.1 Gy. Mean urethra BED D10 was 230.3±33.9 Gy. Mean bladder BED was 35.2±11.0 Gy. Mean rectum BED D2cc was 85.6±24.3 Gy. Significant dosimetric differences between toxicity grades were found for mean bladder BED, bladder D15, and rectum D50, but differences between individual means were not statistically significant. Given the low incidence of grade 3 GU and GI toxicity, we propose urethra D10 <200 Gy, rectum D2cc <60 Gy, and bladder D15 <45 Gy as preliminary dose constraints for combined modality therapy. We successfully applied our dose integration technique to a sample of patients with intermediate- and high-risk prostate cancer. Incidence of grade 3 toxicity was low, suggesting that combined doses observed in this study were safe. We suggest preliminary dose constraints as a conservative starting point to investigate and escalate prospectively in a future study.