Volumetric Modulated Arc Radiotherapy Research Articles

HyperArc performance in radiotherapy and its correlations with number and volume of multiple brain metastases

ObjectiveTo assess the performance and advantages of HyperArc for radiotherapy of multiple brain metastases with dosimetric parameters with respect to coplanar volumetric modulated arc radiotherapy (c-VMAT), and characterize implicit correlations between tumor features and dosimetric parameters. MethodsThis retrospective study involved 40 patients with multiple brain metastases (4-16 tumors, 12.8-240.8 cm3) who received simultaneous radiotherapy at the Department of Radiation Oncology, Shenzhen People's Hospital from January 2019 to December 2022. Both HyperArc and c-VMAT plans were designed by the same and qualified physicist using the Eclipse system with Truebeam. A single isocenter and a 6 MV flattening filter-free (6FFF) photon beam were used for radiotherapy of multiple brain metastases in each plan. Dosimetric parameters of tumors and organs at risk (OARs) were compared between HyperArc and c-VMAT plans. Correlations between tumor features (number and volume) and dosimetric parameters were revealed and analyzed. Furthermore, monitor units (MUs) of both plan types were recorded to assess rays utilization and delivery efficiency. ResultsCompared to c-VMAT plans, HyperArc plans achieved higher maximum dose (Dmax) (5.23%, t=7.87, P<0.01), but lower minimum dose (Dmin) (3.94%, t=-2.12, P=0.04) and mean dose (Dmean) (1.05%, t=-3.29, P<0.01) for planning gross tumor volumes (PGTVs). The conformity index (CI), homogeneity index (HI), gradient index (GI) and R50% of PGTVs with HyperArc were better than those with c-VMAT, with the improvements of 20.78%, 1.68%, 19.83% and 36.20%, respectively (P<0.01). The dosimetric parameters of OARs were significantly improved in HyperArc plans compared to c-VMAT plans. Specifically, the Dmax and the Dmean to the brainstem decreased by 16.14% and 11.37%, respectively. The Dmax for eye_L decreased by 16.88%, for eye_R decreased by 11.67%, for optical nerve_L decreased by 12.56%, and for chiasm decreased by 18.12%. Few correlations were observed between the differences of CI/ HI/ GI/ R50% and the number of PGTVs between the two plan types. Whereas, regression analysis indicated that the differences of CI/ GI/ R50% were negatively correlated with the volume of PGTVs, respectively. Moreover, although HyperArc plans reduced the MUs by 4.74% compared to c-VMAT, no significant difference was observed (P>0.05). ConclusionsThis study demonstrates the promising performance of HyperArc for radiotherapy of multiple brain metastases, including better dose conformity for the tumors, more rapid dose drop and less dose spillage outside the tumors area, effective reduction of dose bridges among close tumors, and sparing OARs. It also reveals the correlations between the number or volume of tumors and dose parameters, which can help optimize the use of HyperArc and predict clinical benefits.

Patterns of quality assurance and treatment planning for stereotactic body radiation therapy in India - A survey.

The use of stereotactic body radiation therapy (SBRT) is an increasing trend in the country. The aim of this study is to gain knowledge on patterns of quality assurance (QA) and treatment planning (TP) aspects with respect to SBRT. A questionnaire with multiple choice was designed to determine practices of SBRT covering areas such as years of experience, type of linear accelerator, tumor-motion strategies, calculation algorithm used in the TP system (TPS), the protocol used for small field dosimetry, the detector used for small field dosimetry and QA, respiratory management during delivery. The survey was sent to all radiotherapy institutes in the country having a minimum of one linear accelerator, and responses were analyzed. From June 2022 to December 2022, 265 responses to the SBRT survey were received with response rate as 60.4%. The most common reason for not adopting SBRT was reported as a lack of capability of treatment machines to deliver SBRT (61.6%). Lung (81.1%) was the most practiced site. The most common delivery unit was a conventional linear accelerator (83%); 6 MV FFF (85.7%) was mostly used energy; volumetric-modulated arc radiotherapy (VMAT) (91.5%) was mostly used delivery technique; most of the equipment (more than 91.5%) used multileaf collimator (MLC) leaf width ≤5 mm. The most popular methods used for motion strategies during computed tomography (CT) were motion-encompassing and breath-hold techniques used by 65 (62.5%) and 62 (59.6%) respondents, respectively. The most popular method used for respiratory management during delivery was breath-hold by 55 (52.4%) respondents. Most TPS are equipped with either Type-C or Type-B algorithms. Heterogeneity was observed in the QA protocol and acceptance criteria for analysis of patient-specific QA. The survey resulted in heterogeneity in QA and TP aspects among users of SBRT and demands for harmonizing the dosimetric aspects of SBRT in the country.

Channel-wise attention enhanced and structural similarity constrained cycleGAN for effective synthetic CT generation from head and neck MRI images

BackgroundMagnetic resonance imaging (MRI) plays an increasingly important role in radiotherapy, enhancing the accuracy of target and organs at risk delineation, but the absence of electron density information limits its further clinical application. Therefore, the aim of this study is to develop and evaluate a novel unsupervised network (cycleSimulationGAN) for unpaired MR-to-CT synthesis.MethodsThe proposed cycleSimulationGAN in this work integrates contour consistency loss function and channel-wise attention mechanism to synthesize high-quality CT-like images. Specially, the proposed cycleSimulationGAN constrains the structural similarity between the synthetic and input images for better structural retention characteristics. Additionally, we propose to equip a novel channel-wise attention mechanism based on the traditional generator of GAN to enhance the feature representation capability of deep network and extract more effective features. The mean absolute error (MAE) of Hounsfield Units (HU), peak signal-to-noise ratio (PSNR), root-mean-square error (RMSE) and structural similarity index (SSIM) were calculated between synthetic CT (sCT) and ground truth (GT) CT images to quantify the overall sCT performance.ResultsOne hundred and sixty nasopharyngeal carcinoma (NPC) patients who underwent volumetric-modulated arc radiotherapy (VMAT) were enrolled in this study. The generated sCT of our method were more consistent with the GT compared with other methods in terms of visual inspection. The average MAE, RMSE, PSNR, and SSIM calculated over twenty patients were 61.88 ± 1.42, 116.85 ± 3.42, 36.23 ± 0.52 and 0.985 ± 0.002 for the proposed method. The four image quality assessment metrics were significantly improved by our approach compared to conventional cycleGAN, the proposed cycleSimulationGAN produces significantly better synthetic results except for SSIM in bone.ConclusionsWe developed a novel cycleSimulationGAN model that can effectively create sCT images, making them comparable to GT images, which could potentially benefit the MRI-based treatment planning.

PET/CT-Based Radiogenomics Supports KEAP1/NFE2L2 Pathway Targeting for Non-Small Cell Lung Cancer Treated with Curative Radiotherapy.

In lung cancer patients, radiotherapy is associated with a increased risk of local relapse (LR) when compared with surgery but with a preferable toxicity profile. The KEAP1/NFE2L2 mutational status (MutKEAP1/NFE2L2) is significantly correlated with LR in patients treated with radiotherapy but is rarely available. Prediction of MutKEAP1/NFE2L2 with noninvasive modalities could help to further personalize each therapeutic strategy. Methods: Based on a public cohort of 770 patients, model RNA (M-RNA) was first developed using continuous gene expression levels to predict MutKEAP1/NFE2L2, resulting in a binary output. The model PET/CT (M-PET/CT) was then built to predict M-RNA binary output using PET/CT-extracted radiomics features. M-PET/CT was validated on an external cohort of 151 patients treated with curative volumetric modulated arc radiotherapy. Each model was built, internally validated, and evaluated on a separate cohort using a multilayer perceptron network approach. Results: The M-RNA resulted in a C statistic of 0.82 in the testing cohort. With a training cohort of 101 patients, the retained M-PET/CT resulted in an area under the curve of 0.90 (P < 0.001). With a probability threshold of 20% applied to the testing cohort, M-PET/CT achieved a C statistic of 0.7. The same radiomics model was validated on the volumetric modulated arc radiotherapy cohort as patients were significantly stratified on the basis of their risk of LR with a hazard ratio of 2.61 (P = 0.02). Conclusion: Our approach enables the prediction of MutKEAP1/NFE2L2 using PET/CT-extracted radiomics features and efficiently classifies patients at risk of LR in an external cohort treated with radiotherapy.

Evaluation of Heart Substructures as a Function of Dose and Radiation-Induced Toxicities in Left-Sided Breast Cancer Radiotherapy

Background. A group of cardiopathies (ischemic, arrhythmic, and pericardial cardiac events) were shown to be associated with doses received by heart substructures following radiotherapy, alerting about the importance of dosimetric evaluation of cardiac structures besides the heart. The aim of this study was to assess the dosimetry of heart and heart substructures of left-sided breast cancer radiotherapy to evaluate possible radiation-induced complications. Methods and Materials. The study enrolled 20 patients treated with 3D-conformal radiotherapy (3DCRT), while intensity-modulated (IMRT) and volumetric-modulated arc radiotherapy (VMAT) plans were simulated for comparative purposes. The organs at risk (OARs) of interest were the heart, ascending aorta, descending aorta, left ventricle, left atrium, right ventricle, right atrium, superior vena cava, inferior vena cava, and pulmonary artery. Results. The percentage of left ventricle included in the radiation field was &gt;5% for all plans (8.92% 3DCRT, 8.30% IMRT, and 6.84% VMAT). A strong correlation between mean heart dose and the percentage of left ventricle overlapping with the radiation fields was observed in 3DCRT (r = 0.784) and IMRT (r = 0.755) plans, and a moderate correlation was shown between tumor volume and the percentage of left ventricle included in the radiation field for all plans. A moderate correlation was observed between body mass index and cardiac structures for the mean dose to the right ventricle (r = 0.640) in conformal plans and V5 of heart (r = 0.528) and left ventricle (r = 0.669) in volumetric-modulated plans. Additionally, moderate to strong correlations were found between maximum heart distance and heart dose in both conformal and modulated plans. Conclusions. Considering possible occurrences of cardiac events during or postradiotherapy, monitoring the heart and its substructures and setting dosimetric thresholds for healthy tissues must be a priority to achieve a personalized and effective treatment.

TransQA: deep hybrid transformer network for measurement-guided volumetric dose prediction of pre-treatment patient-specific quality assurance

Objective. Performing pre-treatment patient-specific quality assurance (prePSQA) is considered an essential, time-consuming, and resource-intensive task for volumetric modulated arc radiotherapy (VMAT) which confirms the dose accuracy and ensure patient safety. Most current machine learning and deep learning approaches stack excessive convolutional/pooling operations (CPs) to predict prePSQA with two-dimensional or one-dimensional information input. However, these models generally present limitations in explicitly modeling long-range dependency for volumetric dose prediction due to the loss of spatial dose features and the inherent locality of CPs. The purpose of this work is to construct a deep hybrid network by combining the self-attention mechanism-based Transformer with modified U-Net for predicting measurement-guided volumetric dose (MDose) of prePSQA. Approach. The enrolled 307 cancer patients underwent VMAT were randomly divided into 246 and 61 cases for training and testing the model. The input data included computed tomography images, radiotherapy dose images exported from the treatment planning system, as well as the MDose distribution from the verification system. The output was the predicted high-quality voxel-wise prePSQA dose distribution. Main results: qualitative and quantitative experimental results show that the proposed prediction method could achieve comparable or better performance on MDose prediction over other approaches in terms of spatial dose distribution, dose–volume histogram metrics, gamma passing rates, mean absolute error, root mean square error, and structural similarity. Significance. The preliminary results on multiple cancer sites show that our approach can be taken as a clinical guidance tool and help medical physicists to reduce the measurement work of prePSQA.

A pilot study of stereotactic body radiotherapy combined with pelvic radiotherapy and GTVp boost based on multiparameter magnetic resonance image in patients with high-risk prostate cancer.

This pilot study aimed to explore the preliminary effects and safety of stereotactic body radiotherapy (SBRT) combined with preventive pelvic radiotherapy and primary gross tumor volumes (GTVp) boost in patients with high-risk prostate cancer based on multiparameter magnetic resonance image (mpMRI). Tumors were contoured as GTVp based on mpMRI. The prostate and proximal seminal vesicles were considered as the clinical target volume1. The pelvic lymphatic drainage area constituted clinical target volume 2. Radiation doses were 40Gy or 45Gy/5fractions to planning target volume of primary tumor, 37.5Gy/5f to prostate, seminal vesicle, and positive pelvic lymph nodes, and 25Gy/5f to pelvic synchronously. The treatment was delivered 3 times per week. Volumetric modulated arc radiotherapy and intensity-modulated radiotherapy were used to complete SBRT. The genitourinary (GU) and gastrointestinal (GI) toxicities were evaluated. Quality of life data was also captured. A total of 15 patients were enrolled in this study with a median age of 78 (56-87) from 2017 to 2020. All patients received SBRT. At 3 months after radiotherapy, the proportion of PSA < 0.006 ng/mL was 66.7% (10/15). The 2-year biochemical relapse-free survival was 93.3%. The incidence of grade 1 acute GU side effects was 80% (12/15); the incidence of acute grade 1 GI toxicity was 66.7% (10/15); and no grade 2 or higher acute GU and GI side effects was observed. Two patients presented with temporary late grade 2 GI toxicity. International Prostatic System Score increased rapidly after a transient increase at 1 week (P = .001). There were no significant differences in EORTC quality of life scores in all domains except global health status. In this pilot study, it was revealed that SBRT combined with preventive pelvic radiotherapy and GTVp boost based on mpMRI image was effective and well tolerated for patients with high-risk prostate cancer.

Left Anterior Descending Coronary Artery-Optimized Knowledge-Based Radiotherapy Planning in Patients with Locally Advanced Non-Small Cell Lung Cancer

The left anterior descending (LAD) coronary artery volume receiving 15 Gy (V15 Gy) has been associated with major adverse cardiac events and mortality in patients with locally advanced non-small cell lung cancer (LA-NSCLC) treated with radiotherapy (RT). However, coronary arteries are not routinely contoured as standard-of-care and there is limited data describing coronary-sparing planning techniques. Our objective was to evaluate whether LAD-sparing could be improved compared to real-world plans using a commercial knowledge-based planning (KBP) software without clinically unacceptable tradeoffs to other critical organs at risk (OAR). Retrospective replanning analysis was conducted on 31 RT plans developed for patients with LA-NSCLC. Each case was manually replanned with volumetric modulated arc radiotherapy (VMAT) optimized for LAD V15 Gy sparing with a prescription dose of 60 Gy. The resulting plans were used to create an LAD-optimized KBP model. The model included both KBP-generated objectives and additional point objectives to meet LAD (V15 Gy < 10%), lung (V5 Gy < 60%, V20 < 30%, mean < 17 Gy), heart (mean < 20 Gy), spinal cord (D0.03cc < 45 Gy), esophagus (V60 Gy < 17%, mean < 34 Gy), and planning target volume (PTV; D95% = 100%). The LAD-optimized model was deployed to replan 33 additional VMAT plans for LA-NSCLC with prescription dose 60 Gy, delivered between 2018 and 2022. Dose constraints or objectives were only unmet with KBP when not met in the original plan. Descriptive statistics were used to compare dosimetric parameters between original and LAD-optimized KBP plans. For the 33 plans identified for LAD-optimized KBP replanning, the original plans had a mean LAD V15 Gy of 17.9% (standard error [SE], 3.9%), while the LAD-optimized KBP plans had a significantly lower mean LAD V15 Gy of 5.9% (SE, 1.9%; p = 0.031). There was no significant difference in mean heart dose between the original and LAD-optimized KBP plans (8.4 Gy [SE 6.6 Gy] vs. 7.3 Gy [SE 5.8 Gy]; p = 0.48). Of these 33 KBP plans, 42% (n = 14) had mean reductions in LAD V15 Gy from 40.5% (SE 4.3%) to 10.5% (SE 3.5%; p = 0.0002), with 9/14 now able to meet < 10%, without affecting other critical OAR objectives (p > 0.5 for lungs, esophagus, spinal cord). 45% (n = 15) originally had an LAD V15 Gy < 1%, which were unchanged using KBP (p > 0.3). Four plans (12%) had higher LAD V15 Gy in the KBP vs. original plan (2/4 still meeting < 10%), due to the model prioritizing other OARs to a greater degree. Improvements in LAD-sparing was achievable in more than 40% of plans without apparent clinically significant tradeoffs in other critical OARs and without corresponding change in MHD. This result underscores the importance of standard implementation of LAD contouring and dose constraints, particularly given the discordance between whole heart and LAD dose exposure.

High Dose Hyperfractionated Thoracic Radiotherapy vs. Standard Dose for Limited Stage Small-Cell Lung Cancer: A Multicenter, Open-Label Randomized, Phase 3 Trial

Limited stage small-cell lung cancer (LS-SCLC) is associated with poor prognosis. We aimed to assess the efficacy and safety of high-dose, hyperfractionated thoracic radiotherapy of 54 Gy in 30 fractions compared with standard dose (45 Gy in 30 fractions) as a first-line treatment for LS-SCLC. The study was an open-label, randomized, phase 3 trial, done at 16 public hospitals in China. Key inclusion criteria were patients aged 18-70 years, with previously histologically or cytologically confirmed LS-SCLC, previously untreated or received 1-2 courses of intravenous cisplatin (75 mg/m²of body-surface area, on day 1 or divided into two days of each cycle) or carboplatin (area under the curve of 5 mg/mL per min, day 1 of each cycle)and intravenous etoposide (100 mg/m²of body-surface area, on days 1-3 of each cycle), and an Eastern Cooperative Oncology Group (ECOG) performance status of 0-1.Eligible patients were randomly assigned (1:1) to receive volumetric-modulated arc radiotherapy (VMAT) of 45 Gy in 30 fractions or the simultaneous integrated boost VMAT (SIB-VMAT) of 54 Gy in 30 fractions to the primary lung tumor and lymph node metastases starting 0-42 days after the first chemotherapy course. Both groups of patients received thoracic radiotherapy twice per day and 10 fractions per week. Prophylactic cranial radiation (PCI, 25 Gy in 10 fractions) was implemented to patients with responsive disease. The primary endpoint was overall survival. Safety was analyzed in the as-treated population. Between June 30, 2017, and April 6, 2021, 224 eligible patients were enrolled and randomly assigned to 54 Gy (n = 108) or 45 Gy (n = 116). Median follow-up for the primary analysis was 45 months (IQR 41-48). Median overall survival was significantly improved in the 54 Gy group (62.4 months) compared with the 45 Gy group (43.1 months; p = 0.001). Median progression-free survival was significantly improved in the 54 Gy group (30.5 months) compared with the 45 Gy group (16.7 months; p = 0.044). The most common grade 3-4 adverse events were neutropenia (30 [28%] of 108 patients in the 54 Gy group vs 27 [23%] of 116 patients in the 45 Gy group), neutropenic infections (6 [6%] vs 2 [2%]), thrombocytopenia (13 [12%] vs 12 [10%]), anemia (6 [6%] vs 4 [3%]), and esophagitis (1 [1%] vs 3 [3%]). Treatment-related serious adverse events occurred in 9 [8%] patients in the 54 Gy group and 16 [14%] patients in the 45 Gy group. There were one treatment-related deaths in 54 Gy group (myocardial infarction). Compared with standard thoracic radiotherapy dose of 45 Gy, the high dose of 54 Gy improved overall survival and progression-free survival without increasing toxicities in patients with LS-SCLC, supporting twice-daily hyperfractionated thoracic radiotherapy of 54 Gy with concurrent chemotherapy is an alternative treatment option for LS-SCLC. This study is complete and registered with ClinicalTrials.gov, NCT03214003.

Comparison of the dose distribution of the VMAT radiotherapy technique depending on the beam used: FFF-X10MV and FFF-X15MV.

The aim of the study was to answer the question of whether flattening filter (FF) and flattening filter-free (FFF) beams can be used alternately in the volumetric modulated arc therapy (VMAT) treatment technique, regardless of the size of the irradiated volume [small (S) or large (L) planning target volume (PTV)]. Two groups of patients were examined: a group with a S-PTV-laryngeal cancer and a group with a L-PTV - gynecological volume. For each patient, two treatment plans were made for beams (energies): FFF-X10MV and FF-X15MV. Then, a statistical analysis, nonparametric test, and independent groups were performed, comparing the beams' impact on the analyzed treatment plans. In the case of laryngeal irradiation (S-PTV), there are no statistically significant differences between the energy used and the assessed parameters of the plan. In the case of gynecological volume (L-PTV), only statistically significant differences were noted for the number of monitor units depending on the energy used. For a large irradiated volume (gynecological case), the use of FFF beams increases the number of monitor units by 39,4% in relation to the FF beam. In the case of gynecological neoplasms, statistically significant differences were found in the number of monitor units. Therefore, in the case of irradiation of L-PTV, it is recommended that flattening-filtering beams are used due to the smaller number of monitors. In the case of S-PTV, no statistically significant differences were found between the types of beams used (FF or FFF) and the treatment plan parameters analyzed in the study.

Advantage of Adding Non-Coplanar Arcs for Scalp-Avoidance Whole-Brain Irradiation with Volumetric-Modulated Arc Radiotherapy to Reduce Scalp Dose in Pediatric Patients with Medulloblastomas

With increasing long-term survival, permanent alopecia has received much attention as a crucial late adverse effect in pediatric patients with medulloblastoma. Therefore, we performed scalp-avoidance whole-brain irradiation with volumetric-modulated arc therapy (SAWB-VMAT) as a component of craniospinal irradiation. We have previously reported that SAWB-VMAT significantly reduced the scalp equivalent doses in 2 Gy per fraction (assuming α/β = 2) to 50% of the areas (EQD50%) compared to conventional WBRT, and the estimated cut-off EQD50% was 19.9 Gy for severe permanent alopecia. In SAWB-VMAT with two coplanar arcs, there were cases with the high-risk disease in which radiation oncologists and medical physicists had difficulty in reducing the scalp dose below the cut-off EQD50%. Therefore, to investigate the utility of adding non-coplanar arcs to reduce the scalp dose, we conducted a planning study to compare the scalp EQD50% and the dose to the organ at risk (OAR) in VMAT with two coplanar arcs (Co2arcVMAT), VMAT with three coplanar arcs (Co3arcVMAT), and VMAT with two coplanar and two non-coplanar arcs (NcVMAT). Co2arcVMAT, Co3arcVMAT, and NcVMAT plans were created for 10 pediatric patients with medulloblastoma. The planned target volume (PTV) for SAWB-VMAT included regions of the whole brain, cervical spinal cord, cerebrospinal fluid space, and intervertebral foramen. The prescribed dose for the PTV was 35.2 Gy in 22 fractions, and all plans were normalized to ensure that V90 = 99%. The scalp EQD 50% was evaluated separately for four areas (top, back, left, and right) according to anatomical structures in each case. In addition, we also calculated normalized scalp EQD50% values (NV_EQD50%scalp), and Co2arcVMAT was set to unity. The eye, lens, hypopharynx, cochlea, thyroid, oral cavity, and parotid gland were defined as other OARs. The median EQD50% of the top area of the scalp was 21.8 Gy, 22.0 Gy, and 18.2 Gy for Co2arcVMAT, Co3arcVMAT, and NcVMAT, respectively. The scalp EQD50% of the top area in NcVMAT was significantly reduced than in Co2arcVMAT and Co3arcVMAT (P-value < 0.05). The median EQD50% of the top area of the scalp for NcVMAT was < 19.9 Gy, which was the cut-off dose for severe permanent alopecia. The NV_EQD50%scalp index of the back area was reduced in a similar manner with statistical significance (Co2arcVMAT, 1.0; Co3arcVMAT, 1.0; and NcVMAT, 0.94) (P-value < 0.001). When considering the dose of indices of other OARs and coverage of PTV, there were no significant differences between the three techniques. SAWB-VMAT with non-coplanar arcs can reduce the scalp EQD50% of the top area below the cut-off dose of 19.9 Gy.

Evaluation of the effect of intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc radiotherapy (VMAT) techniques on survival response in cell lines with a new radiobiological modeling.

The optimal radiobiological model, which assesses the biological effects of novel radiotherapy techniques that concurrently modify multiple physical factors, has not yet been defined. This study aimed to investigate the impact of intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) on cellular response in head and neck cancer and melanoma models. Clonogenic analysis, DNA double-strand break analysis, apoptosis, and cell cycle analysis were performed on cancer stem cell models, cancer models, and normal tissue cell models to assess radiation sensitivity. The segmented radiation approach used in IMRT applications enhanced radiosensitivity and cytotoxicity in the cancer models, while changes in dose rate had varying effects on cytotoxicity depending on the tumor cell type. VMAT increased cellular resistance, favoring treatment outcomes. The biological processes were influenced differently by dose rate, IMRT, and VMAT depending on the tumor cell type. The selection of the most appropriate technique is crucial in representing new radiotherapy approaches. The obtained data can serve as a model to address clinical questions in daily practice. The integration of non-standard outcomes with standard applications should be considered in clinical settings.

Dosimetric comparison between RapidArc and HyperArc in hippocampal-sparing whole-brain radiotherapy with a simultaneous integrated boost

The HyperArc technique is known for generating high-quality radiosurgical treatment plans for intracranial lesions or hippocampal-sparing whole-brain radiotherapy (WBRT). However, there is no reported feasibility of using the HyperArc technique in hippocampal-sparing WBRT with a simultaneous integrated boost (SIB). This study aimed to compare dosimetric parameters of 2 commercially-available volumetric-modulated arc radiotherapy techniques, HyperArc and RapidArc, when using hippocampal-sparing WBRT with a SIB to treat brain metastases.Treatment plans using HyperArc and RapidArc techniques were generated retrospectively for 19 previously treated patients (1 to 3 brain metastases). The planning target volumes for the whole brain (excluding the hippocampal avoidance region; PTVWB) and metastases (PTVmet) were prescribed 25 and 45 Gy, respectively, in 10 fractions. Each plan included homogeneous and inhomogeneous delivery to the PTVmet. Dosimetric parameters for the target (conformity index [CI], homogeneity index [HI], target coverage [D95%]), and nontarget organs at risk were compared for the HyperArc and RapidArc plans.For homogeneous delivery, dosimetric parameters, including mean CI, HI, and target coverage in PTVWB and PTVmet, were superior for HyperArc than RapidArc plans (all p < 0.01). The PTVWB and PTVmet target coverage for HyperArc plans was significantly greater than for RapidArc plans (96.17% vs 93.38%, p < 0.01; 94.02% vs 92.21%, p < 0.01, respectively). HyperArc plans had significantly lower mean hippocampal Dmax and Dmin values than RapidArc plans (Dmax: 15.53 Gy vs, 16.71 Gy, p < 0.01; Dmin: 8.33 Gy vs 8.93 Gy, p < 0.01, respectively). Similarly, inhomogeneous delivery of hyperArc produced a superior target and lower hippocampal dosimetric parameters than RapidArc, except for the HI of PTVmet (all p < 0.01).HyperArc generated superior conformity and target coverage with lower hippocampal doses than RapidArc. HyperArc could be an attractive technique for hippocampal-sparing WBRT with an SIB.

Dosimetric comparison between intensity-modulated radiation therapy and volumetric-modulated arc therapy to enhance bladder and bowel.

Prostate cancer is the second most common cancer in men. Two common radiotherapy techniques, intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc radiotherapy (VMAT), are used for treatment. This study aimed to compare the two techniques for sparing the bladder and bowel. Computed tomography data from prostate cancer patients were analyzed to define the clinical target volume (CTV) and planning target volume (PTV). Treatment plans were generated with Monte Carlo algorithms, and dosimetric analysis was performed using the Monaco Treatment Planning System (TPS). We compared IMRT and VMAT for prostate cancer PTV coverage (% Ref. Volume), with VMAT showing slightly better coverage (98.885±1.704) compared to IMRT (98.594±0.923). VMAT also demonstrated improved PTV conformity. Additionally, VMAT was superior in sparing the bladder (% V4500<40%), while IMRT performed better in bowel preservation (mean Ref. volume CC<195).

23 A Retrospective Study Comparing Outcomes in Matched Patients with Poor Prognosis Treated with Targeted Conventional Volumetric Modulated ARC Radiotherapy Versus Whole Brain Radiotherapy for Brain Metastases

23 A Retrospective Study Comparing Outcomes in Matched Patients with Poor Prognosis Treated with Targeted Conventional Volumetric Modulated ARC Radiotherapy Versus Whole Brain Radiotherapy for Brain Metastases

Comparative study of setup errors between new and reused thermoplastic masks in irradiated head and neck cancer patients

Background: The accuracy and precision of patient setup are important in radiotherapy. The thermoplastic mask is used to immobilize head and neck cancer patient. However, the mask is reused for low-income patients. Therefore, the setup error should be evaluated to approve that these patients remain in the exact position during treatment. Objective: To investigate setup errors with the use of thermoplastic masks in head and neck cancer patients and to compare setup errors of new and reused thermoplastic masks. Materials and Methods: Eighty patients who underwent volumetric modulated arc radiotherapy (VMAT) for head and neck cancer lesions were retrospectively evaluated. The setup error, population systematic error, and population random error were calculated. Subsequently, setup errors in patients using the new and reused thermoplastic masks were compared. Results: The population systematic error in the vertical, longitudinal, and lateral directions for new masks was 2.02, 2.27, and 2.13 mm, respectively, and that for reused masks was 2.37, 1.96, and 2.33 mm, respectively. The population random error in the vertical, longitudinal, and lateral direction for new masks was 1.46, 1.54, and 1.57 mm, respectively, and that for reused masks was 1.65, 1.63, and 1.87 mm, respectively. The results showed no statistically significant difference supported by p value &gt; 0.05 in the setup error between using the new and reused thermoplastic masks in all directions. Conclusion: For head and neck radiotherapy, the population setup errors were &lt; 3 mm in all directions. Moreover, thermoplastic masks can be reused in patients with head and neck cancer.

Indian data on response of positive pelvic lymph nodes in carcinoma cervix patients treated with simultaneous integrated boost using volumetric modulated arc radiation therapy

Objectives The percentage of pelvic lymph node positivity in cervical cancer patients varies from 19% in early stages to 68% in advanced cases. Thirty three percent of patients will develop recurrence within 2 years following therapy and 5-year relative survival for patients with affected regional lymph nodes is 57%. Hence, pelvic lymph nodes need to be included in the definitive plan of radiation treatment for better disease control and longer survival. With conventional radiation therapy, dose escalation was not possible because of small bowel constraints. With higher conformity of intensity modulated radiotherapy technique (IMRT), doses to pelvic and abdominal organs can be minimized. The added advantage of simultaneous integrated boost (SIB) is that high dose per fraction is delivered to the gross disease and low dose to the microscopic disease, thereby reducing the total treatment time and improving the therapeutic ratio. Material and Methods Forty one patients presenting to the Department of Radiation Oncology, between January 2016 and June 2017, with newly biopsy proven carcinoma cervix Stage IB to IVA were enrolled in the study and all the investigations were performed. The radiation dose was delivered using volumetric modulated arc therapy plan to a dose of 5000 cGy in 25 fractions to the whole pelvis and 5500 cGy in 25 fractions at 220 cGy per fraction to the involved nodes using SIB along with weekly cisplatin at 40 mg/m2. After completion of external beam radiation, all the patients received three fractions of brachytherapy to a total dose of 21 Gy. Acute toxicities were assessed using RTOG criteria. At 3 months after completion of treatment, all the patients had been followed up with DW MRI of abdomen and pelvis to assess the response. Results Of the 41 carcinoma cervix patients with significantly positive lymph nodes treated with SIB VMAT, 9.8% of the patients (4 patients) had residual nodal disease, 87.8% of the patients (36 patients) had complete response, 19.5% (8 patients) had residual disease of primary disease, and 78% (32 patients) had complete response at 3 months after completion of treatment with only Grade – I and Grade – II toxicities. Conclusion Treatment with SIB VMAT in carcinoma cervix patients with significant pelvic lymph nodes shows very good response with acceptable acute toxicities. But longer follow-up period is required to see if this response translates into better DFS and OS.

Development of a quasi-3D dosimeter using radiochromic plastic for patient-specific quality assurance.

Patient-specific QA verification ensures patient safety and treatment by verifying radiation delivery and dose calculations in treatment plans for errors. However, a two-dimensional (2D) dose distribution is insufficient for detecting information on the three-dimensional (3D) dose delivered to the patient. In addition, 3D radiochromic plastic dosimeters (RPDs) such as PRESAGE® represent the volume effect in which the dosimeters have different sensitivities according to the size of the dosimeters. Therefore, to solve the volume effect, a Quasi-3D dosimetry system was proposed to perform patient-specific QA using predetermined-sized and multiple RPDs. For patient-specific quality assurance (QA) in radiation treatment, this study aims to assess a quasi-3D dosimetry system using an RPD. Gamma analysis was performed to verify the agreement between the measured and estimated dose distributions of intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT). We fabricated cylindrical RPDs and a quasi-3D dosimetry phantom. A practicability test for a pancreatic patient utilized a quasi-3D dosimetry device, an in-house RPD, and a quasi-3D phantom. The dose distribution of the VMAT design dictated the placement of nine RPDs. Moreover, a 2D diode array detector was used for 2D gamma analysis (MapCHECK2). The patient-specific QA was performed for IMRT, VMAT, and stereotactic ablative radiotherapy (SABR) in 20 prostate and head-and-neck patients. For each patient, six RPDs were positioned according to the dose distribution. VMAT SABR and IMRT/VMAT plans employed a 2%/2mm gamma criterion, whereas IMRT/VMAT plans used a 3%/2mm gamma criterion, a 10% threshold value, and a 90% passing rate tolerance. 3D gamma analysis was conducted using the 3D Slicer software. The average gamma passing rates with 2%/2mm and 3%/3 mm criteria for relative dose distribution were 91.6%±1.4% and 99.4%±0.7% for the 3D gamma analysis using the quasi-3D dosimetry system, respectively, and 97.5% and 99.3% for 2D gamma analysis using MapCHECK2, respectively. The 3D gamma analysis for patient-specific QA of 20 patients showed passing rates of over 90% with 2%/2mm, 3%/2mm, and 3%/3mm criteria. The quasi-3D dosimetry system was evaluated by performing patient-specific QAs with RPDs and quasi-3D phantom. The gamma indices for all RPDs showed more than 90% for 2%/2mm, 3%/2mm, and 3%/3mm criteria. We verified the feasibility of a quasi-3D dosimetry system by performing the conventional patient-specific QA with the quasi-3D dosimeters.

Successful management of Australian patients with locally advanced keratinocyte cancer (KC) and/or extensive skin field cancerization (ESFC), using widefield volumetric arc radiation therapy (VMAT): Report with 24-month follow-up.

9586 Background: Keratinocyte cancer (KC) diagnoses are associated with an elevated risk of developing new skin lesions. Patients with extensive skin field cancerization (ESFC) have large areas (generally ≥50cm2) of actinic keratoses and often, frequent keratinocyte cancers, necessitating repeated interventions. Volumetric modulated arc radiation therapy (VMAT) can precisely target large, complex surfaces with modulated doses, as required, leading to its increasing application to ESFC +/- KC. This is a follow-up 24-month report on the efficacy, safety, cosmetic, and quality of life outcomes of VMAT in the management of patients with ESFC +/- KC at Australian facilities. Methods: Two hundred and twenty-four fields for 194 patients with ESFC +/- KC have been prescribed widefield VMAT and prospectively enrolled in the National (Australian) Dermatology Radiation Oncology Registry (NDROR). One hundred and six fields are now beyond 24-months post-treatment. Over 80% of patients had received up to 4 prior non-radiotherapy interventions. Fields included lower and upper limb, face, scalp, or trunk regions. 3-, 6-, 12-, 18-, and 24-month follow-up assessments rated the percentage of field clearance, lesion response, new lesion events, cosmesis using the Lovett’s scale, toxicity based on CTCAE, and quality of life as assessed using a EQ-5D-5L visual analogue scale (VAS). Results: Median dose delivered to ESFC-only and ESFC + KC fields were 45 Gy (16.2-60 Gy) and 47 Gy (22-60 Gy), respectively, in 25 daily fractions (7-30) across 7 weeks (2-13). At 24-month follow-up of 106 fields, 96% and 94% of ESFC-only and ESFC + KC fields, respectively had clinical success, defined as &gt; 90% field clearance. Cosmesis was graded excellent or good in 98% of fields. The incidence of new KC within the field out to 24-months was 11%. Grade 1-2 radiation dermatitis was induced in all fields during treatment, but resolved by 3-month follow-up. Six percent of fields exhibited grade 3 dermatitis. Twelve percent of patients discontinued treatment due to acute toxicities (Median 88% dose delivered). The most common persistent toxicity at 24-month follow-up was localized grade 1-2 xerosis (51%), alopecia (43%), and/or pruritis (8%). Quality of life was sustainably improved in patients at 24-month follow-up (3.67; p= 0.026). Conclusions: Widefield VMAT has a promising profile of clinical efficacy, safety, and cosmesis in patients with ESFC +/- KC for whom other therapies had failed. Treatment was also associated with significant and durable improvements in quality of life. While long-term follow-up of patients continues, these results provide further support for widefield VMAT as a suitable option for patients with increasingly unmanageable presentations of ESFC and locally-advanced KC. Clinical trial information: ACTRN12618000627257 .

Efficacy and safety of high dose twice-daily thoracic radiotherapy versus standard dose for limited stage small-cell lung cancer: A multicentre, open-label randomised, phase 3 trial.

8587 Background: We aimed to assess the efficacy and safety of high-dose, hyperfractionated thoracic radiotherapy of 54 Gy in 30 fractions compared with standard dose(45 Gy in 30 fractions) as a first-line treatment for LS-SCLC. Methods: The study was an open-label, randomised, phase 3 trial, done at 16 public hospitals in China.Key inclusion criteria were patients aged 18-70 years, with previously histologically or cytologically confirmed LS-SCLC, previously untreated or received 1-2 courses of intravenous cisplatin (75 mg/m²of body-surface area, on day 1 or divided into two days of each cycle) or carboplatin (area under the curve of 5 mg/mL per min, day 1 of each cycle)and intravenous etoposide (100 mg/m²of body-surface area, on days 1-3 of each cycle), and an Eastern Cooperative Oncology Group (ECOG) performance status of 0-1.Eligible patients were randomly assigned (1:1) to receive receive volumetric-modulated arc radiotherapy (VMAT) of 45 Gy in 30 fractions or the simultaneous integrated boost VMAT (SIB-VMAT) of 54 Gy in 30 fractions to the primary lung tumour and lymph node metastases starting 0-42 days after the first chemotherapy course. Both groups of patients received thoracic radiotherapy twice per day and 10 fractions per week.Prophylactic cranial radiation (PCI, 25Gy in 10 fractions) was implemented to patients with responsive disease. The primary endpoint was overall survival. Safety was analysed in the as-treated population. This study is complete and registered with ClinicalTrials.gov,NCT03214003. Results: Between June 30, 2017, and April 6, 2021, 224 eligible patients were enrolled and randomly assigned to 54 Gy (n = 108) or 45 Gy (n = 116).Median follow-up for the primary analysis was 45 months (IQR 41-48). Median overall survival was significantly improved in the 54 Gy group (62.4 months ) compared with the 45 Gy group (43.1 months; p = 0.001). Median progression-free survival was significantly improved in the 54 Gy group (30.5 months) compared with the 45 Gy group (16.7 months; p = 0.044). The most common grade 3-4 adverse events were neutropenia (30 [28%] of 108 patients in the 54 Gy group vs 27 [23%] of 116 patients in the 45 Gy group), neutropenic infections (6 [6%] vs 2 [2%]), thrombocytopenia (13 [12%] vs 12 [10%]), anaemia (6 [6%] vs 4 [3%]), and oesophagitis (1 [1%] vs 3 [3%]). There were one treatment-related deaths in 54 Gy group (myocardial infarction). Conclusions: Compared with standard thoracic radiotherapy dose of 45 Gy, the high dose dose of 54 Gy improved overall survival and progression-free survival without increasing toxicities in patients with LS-SCLC, supporting twice-daily hyperfractionated thoracic radiotherapy of 54 Gy with concurrent chemotherapy is an alternative treatment option for LS-SCLC. Clinical trial information: NCT03214003 .