[Research on Position Verification of Multi-Leaf Collimator (MLC) and Dose Verification Based on Electronic Portal Imaging Device].

Objective: A quality control (QC) system based on the electronic portal imaging device (EPID) system was used to realize the Multi-Leaf Collimator (MLC) position verification and dose verification functions on Primus and VenusX accelerators. Methods: The MLC positions were calculated by the maximum gradient method of gray values to evaluate the deviation. The dose of images acquired by EPID were reconstructed using the algorithm combining dose calibration and dose calculation. The dose data obtained by EPID and two-dimensional matrix (MapCheck/PTW) were compared with the dose calculated by Pinnacle/TiGRT TPS for γ passing rate analysis. Results: The position error of VenusX MLC was less than 1 mm. The position error of Primus MLC was significantly reduced after being recalibrated under the instructions of EPID. For the dose reconstructed by EPID, the average γ passing rates of Primus were 98.86% and 91.39% under the criteria of 3%/3 mm, 10% threshold and 2%/2 mm, 10% threshold, respectively. The average γ passing rates of VenusX were 98.49% and 91.11%, respectively. Conclusion: The EPID-based accelerator quality control system can improve the efficiency of accelerator quality control and reduce the workload of physicists.

Feasibility of Customized Thermoplastic Patient-Specific Helmet Bolus for Scalp Irradiation Using Volumetric-Modulated Arc Therapy Planning.

Introduction: In this study, we sought to develop a thermoplastic patient-specific helmet bolus that could deliver a uniform therapeutic dose to the target and minimize the dose to the normal brain during whole-scalp treatment with a humanoid head phantom. Methods: The bolus material was a commercial thermoplastic used for patient immobilization, and the holes in the netting were filled with melted paraffin. We compared volumetric-modulated arc therapy treatment plans with and without the bolus for quantitative dose distribution analysis. We analyzed the dose distribution in the region of interest to compare dose differences between target and normal organs. For quantitative analysis of treatment dose, OSLD chips were attached at the vertex (VX), posterior occipital (PO), right (RT), and left temporal (LT) locations. Results: The average dose in the clinical target volume was 6553.8 cGy (99.3%) with bolus and 5874 cGy (89%) without bolus, differing by more than 10% from the prescribed dose (6600 cGy) to the scalp target. For the normal brain, it was 3747.8 cGy (56.8%) with bolus and 5484.6 cGy (83.1%) without bolus. These results show that while the dose to the treatment target decreased, the average dose to the normal brain, which is mostly inside the treatment target, increased by more than 25%. With the bolus, the OSLD measured dose was 102.5 ± 1.2% for VX and 101.5 ± 1.9%, 95.9 ± 1.9%, and 81.8 ± 2.1% for PO, RT, and LT, respectively. In addition, the average dose in the treatment plan was 102%, 101%, 93.6%, and 80.7% for VX, PO, RT, and LT. When no bolus was administered, 59.6 ± 2.4%, 112.6 ± 1.8%, 47.1 ± 1.6%, and 53.1 ± 2.3% were assessed as OSLD doses for VX, PO, RT, and LT, respectively. Conclusion: This study proposed a method to fabricate patient-specific boluses that are highly reproducible, accessible, and easy to fabricate for radiotherapy to the entire scalp and can effectively spare normal tissue while delivering sufficient surface dose.

Multi-institutional evaluation of a Pareto navigation guided automated radiotherapy planning solution for prostate cancer.

BACKGROUND: Current automated planning solutions are calibrated using trial and error or machine learning on historical datasets. Neither method allows for the intuitive exploration of differing trade-off options during calibration, which may aid in ensuring automated solutions align with clinical preference. Pareto navigation provides this functionality and offers a potential calibration alternative. The purpose of this study was to validate an automated radiotherapy planning solution with a novel multi-dimensional Pareto navigation calibration interface across two external institutions for prostate cancer. METHODS: The implemented 'Pareto Guided Automated Planning' (PGAP) methodology was developed in RayStation using scripting and consisted of a Pareto navigation calibration interface built upon a 'Protocol Based Automatic Iterative Optimisation' planning framework. 30 previous patients were randomly selected by each institution (IA and IB), 10 for calibration and 20 for validation. Utilising the Pareto navigation interface automated protocols were calibrated to the institutions' clinical preferences. A single automated plan (VMATAuto) was generated for each validation patient with plan quality compared against the previously treated clinical plan (VMATClinical) both quantitatively, using a range of DVH metrics, and qualitatively through blind review at the external institution. RESULTS: PGAP led to marked improvements across the majority of rectal dose metrics, with Dmean reduced by 3.7 Gy and 1.8 Gy for IA and IB respectively (p < 0.001). For bladder, results were mixed with low and intermediate dose metrics reduced for IB but increased for IA. Differences, whilst statistically significant (p < 0.05) were small and not considered clinically relevant. The reduction in rectum dose was not at the expense of PTV coverage (D98% was generally improved with VMATAuto), but was somewhat detrimental to PTV conformality. The prioritisation of rectum over conformality was however aligned with preferences expressed during calibration and was a key driver in both institutions demonstrating a clear preference towards VMATAuto, with 31/40 considered superior to VMATClinical upon blind review. CONCLUSIONS: PGAP enabled intuitive adaptation of automated protocols to an institution's planning aims and yielded plans more congruent with the institution's clinical preference than the locally produced manual clinical plans.

Cost-effectiveness of intraoperative radiation therapy versus intensity-modulated radiation therapy for the treatment of early breast cancer: a disinvestment analysis.

BACKGROUND: Adjuvant radiotherapy represents a key component in curative-intent treatment for early-stage breast cancer patients. In recent years, two accelerated partial breast irradiation (APBI) techniques are preferred for this population in our organization: electron-based Intraoperative radiation therapy (IORT) and Linac-based External Beam Radiotherapy, particularly Intensity-modulated radiation therapy (IMRT). Recently published long-term follow-up data evaluating these technologies have motivated a health technology reassessment of IORT compared to IMRT. METHODS: We developed a Markov model to simulate health-state transitions from a cohort of women with early-stage breast cancer, after lumpectomy and adjuvant APBI using either IORT or IMRT techniques. The cost-effectiveness from a private health provider perspective was assessed from a disinvestment point of view, using life-years (LYs) and recurrence-free life-years (RFLYs) as measure of benefits, along with their respective quality adjustments. Expected costs and benefits, and the incremental cost-effectiveness ratio (ICER) were reported. Finally, a sensitivity and scenario analyses were performed to evaluate the cost-effectiveness using lower IORT local recurrence and metastasis rates in IORT patients, and if equipment maintenance costs are removed. RESULTS: IORT technology was dominated by IMRT in all cases (i.e., fewer benefits with greater costs). Despite small differences were found regarding benefits, especially for LYs, costs were considerably higher for IORT. For sensitivity analyses with lower recurrence and metastasis rates for IORT, and scenario analyses without equipment maintenance costs, IORT was still dominated by IMRT. CONCLUSIONS: For this cohort of patients, IMRT was, at least, non-inferior to IORT in terms of expected benefits, with considerably lower costs. As a result, IORT disinvestment should be considered, favoring the use of IMRT in these patients.

A Comparative Study of Deep Learning Dose Prediction Models for Cervical Cancer Volumetric Modulated Arc Therapy.

Purpose: Deep learning (DL) is widely used in dose prediction for radiation oncology, multiple DL techniques comparison is often lacking in the literature. To compare the performance of 4 state-of-the-art DL models in predicting the voxel-level dose distribution for cervical cancer volumetric modulated arc therapy (VMAT). Methods and Materials: A total of 261 patients' plans for cervical cancer were retrieved in this retrospective study. A three-channel feature map, consisting of a planning target volume (PTV) mask, organs at risk (OARs) mask, and CT image was fed into the three-dimensional (3D) U-Net and its 3 variants models. The data set was randomly divided into 80% as training-validation and 20% as testing set, respectively. The model performance was evaluated on the 52 testing patients by comparing the generated dose distributions against the clinical approved ground truth (GT) using mean absolute error (MAE), dose map difference (GT-predicted), clinical dosimetric indices, and dice similarity coefficients (DSC). Results: The 3D U-Net and its 3 variants DL models exhibited promising performance with a maximum MAE within the PTV 0.83% ± 0.67% in the UNETR model. The maximum MAE among the OARs is the left femoral head, which reached 6.95% ± 6.55%. For the body, the maximum MAE was observed in UNETR, which is 1.19 ± 0.86%, and the minimum MAE was 0.94 ± 0.85% for 3D U-Net. The average error of the Dmean difference for different OARs is within 2.5 Gy. The average error of V40 difference for the bladder and rectum is about 5%. The mean DSC under different isodose volumes was above 90%. Conclusions: DL models can predict the voxel-level dose distribution accurately for cervical cancer VMAT treatment plans. All models demonstrated almost analogous performance for voxel-wise dose prediction maps. Considering all voxels within the body, 3D U-Net showed the best performance. The state-of-the-art DL models are of great significance for further clinical applications of cervical cancer VMAT.

Effects of bone marrow sparing radiotherapy on acute hematologic toxicity for patients with locoregionally advanced cervical cancer: a prospective phase II randomized controlled study.

OBJECTIVE: To evaluate effects of bone marrow sparing (BMS) radiotherapy on decreasing the incidence of acute hematologic toxicity (HT) for locoregionally advanced cervical cancer (LACC) patients treated by pelvic irradiation. MATERIALS AND METHODS: LACC patients were recruited prospectively from May 2021 to May 2022 at a single center and were evenly randomized into the BMS group and the control group. All patients received pelvic irradiation with concurrent cisplatin (40 mg/m2 weekly), followed by brachytherapy and BM V40 < 25% in the BMS group was additionally prescribed. Acute HT was assessed weekly. Binary logistic regression model and receiver operating characteristic (ROC) curve were used for predictive value analysis. The trial was registered with Chinese clinical trial registry (ChiCTR2200066485). RESULTS: A total of 242 patients were included in the analysis. Baseline demographic, disease and treatment characteristics were balanced between the two groups. In the intention-to-treat population, BMS was associated with a lower incidence of grade ≥ 2 and grade ≥ 3 acute HT, leukopenia and neutropenia s(72.70% v 90.90%, P < 0.001*; 16.50% vs. 65.30%, P < 0.001*; 66.10% vs. 85.10%, P = 0.001*; 13.20% vs. 54.50%, P < 0.001*; 37.20% vs. 66.10%, P < 0.001*; 10.70% vs. 43.80%, P < 0.001*). BMS also resulted in decreased dose delivered to the organs at risk (OARs) including rectum, bladder and left and right femoral head. Univariate and multivariate analyses showed that BM V40 was an independent risk factor for grade ≥ 3 acute HT (odds ratio [OR] = 2.734, 95% confidence interval [CI] = 1.959-3.815, P < 0.001*). Cutoff value was 25.036% and area under the curve (AUC) was 0.786. The nomogram was constructed, which was rigorously evaluated and internally cross-validated, showing good predictive performance. CONCLUSIONS: Receiving BMS pelvic irradiation could reduce the incidence of acute HT in LACC patients, and BM V40 < 25% may be a significant factor in reducing the risks of acute HT.

Pelvic target volume inter-fractional motion during radiotherapy for cervical cancer with daily iterative cone beam computed tomography.

BACKGROUND: Tumor regression and organ movements indicate that a large margin is used to ensure target volume coverage during radiotherapy. This study aimed to quantify inter-fractional movements of the uterus and cervix in patients with cervical cancer undergoing radiotherapy and to evaluate the clinical target volume (CTV) coverage. METHODS: This study analyzed 303 iterative cone beam computed tomography (iCBCT) scans from 15 cervical cancer patients undergoing external beam radiotherapy. CTVs of the uterus (CTV-U) and cervix (CTV-C) contours were delineated based on each iCBCT image. CTV-U encompassed the uterus, while CTV-C included the cervix, vagina, and adjacent parametrial regions. Compared with the planning CTV, the movement of CTV-U and CTV-C in the anterior-posterior, superior-inferior, and lateral directions between iCBCT scans was measured. Uniform expansions were applied to the planning CTV to assess target coverage. RESULTS: The motion (mean ± standard deviation) in the CTV-U position was 8.3 ± 4.1 mm in the left, 9.8 ± 4.4 mm in the right, 12.6 ± 4.0 mm in the anterior, 8.8 ± 5.1 mm in the posterior, 5.7 ± 5.4 mm in the superior, and 3.0 ± 3.2 mm in the inferior direction. The mean CTV-C displacement was 7.3 ± 3.2 mm in the left, 8.6 ± 3.8 mm in the right, 9.0 ± 6.1 mm in the anterior, 8.4 ± 3.6 mm in the posterior, 5.0 ± 5.0 mm in the superior, and 3.0 ± 2.5 mm in the inferior direction. Compared with the other tumor (T) stages, CTV-U and CTV-C motion in stage T1 was larger. A uniform CTV planning treatment volume margin of 15 mm failed to encompass the CTV-U and CTV-C in 11.1% and 2.2% of all fractions, respectively. The mean volume change of CTV-U and CTV-C were 150% and 51%, respectively, compared with the planning CTV. CONCLUSIONS: Movements of the uterine corpus are larger than those of the cervix. The likelihood of missing the CTV is significantly increased due to inter-fractional motion when utilizing traditional planning margins. Early T stage may require larger margins. Personal radiotherapy margining is needed to improve treatment accuracy.

Current practices of craniospinal irradiation techniques in Turkey: a comprehensive dosimetric analysis.

OBJECTIVE: This study evaluates various craniospinal irradiation (CSI) techniques used in Turkish centers to understand their advantages, disadvantages and overall effectiveness, with a focus on enhancing dose distribution. METHODS: Anonymized CT scans of adult and pediatric patients, alongside target volumes and organ-at-risk (OAR) structures, were shared with 25 local radiotherapy centers. They were tasked to develop optimal treatment plans delivering 36 Gy in 20 fractions with 95% PTV coverage, while minimizing OAR exposure. The same CT data was sent to a US proton therapy center for comparison. Various planning systems and treatment techniques (3D conformal RT, IMRT, VMAT, tomotherapy) were utilized. Elekta Proknow software was used to analyze parameters, assess dose distributions, mean doses, conformity index (CI), and homogeneity index (HI) for both target volumes and OARs. Comparisons were made against proton therapy. RESULTS: All techniques consistently achieved excellent PTV coverage (V95 > 98%) for both adult and pediatric patients. Tomotherapy closely approached ideal Dmean doses for all PTVs, while 3D-CRT had higher Dmean for PTV_brain. Tomotherapy excelled in CI and HI for PTVs. IMRT resulted in lower pediatric heart, kidney, parotid, and eye doses, while 3D-CRT achieved the lowest adult lung doses. Tomotherapy approached proton therapy doses for adult kidneys and thyroid, while IMRT excelled for adult heart, kidney, parotid, esophagus, and eyes. CONCLUSION: Modern radiotherapy techniques offer improved target coverage and OAR protection. However, 3D techniques are continued to be used for CSI. Notably, proton therapy stands out as the most efficient approach, closely followed by Tomotherapy in terms of achieving superior target coverage and OAR protection.

A machine learning approach for predicting radiation-induced hypothyroidism in patients with nasopharyngeal carcinoma undergoing tomotherapy.

The purpose of this study was to establish an integrated predictive model that combines clinical features, DVH, radiomics, and dosiomics features to predict RIHT in patients receiving tomotherapy for nasopharyngeal carcinoma. Data from 219 patients with nasopharyngeal carcinoma were randomly divided into a training cohort (n = 175) and a test cohort (n = 44) in an 8:2 ratio. RIHT is defined as serum thyroid-stimulating hormone (TSH) greater than 5.6 µU/mL, with or without a decrease in free thyroxine (FT4). Clinical features, 27 DVH features, 107 radiomics features and 107 dosiomics features were extracted for each case and included in the model construction. The least absolute shrinkage and selection operator (LASSO) regression method was used to select the most relevant features. The eXtreme Gradient Boosting (XGBoost) was then employed to train separate models using the selected features from clinical, DVH, radiomics and dosiomics data. Finally, a combined model incorporating all features was developed. The models were evaluated using receiver operating characteristic (ROC) curves and decision curve analysis. In the test cohort, the area under the receiver operating characteristic curve (AUC) for the clinical, DVH, radiomics, dosiomics and combined models were 0.798 (95% confidence interval [CI], 0.656-0.941), 0.673 (0.512-0.834), 0.714 (0.555-0.873), 0.698 (0.530-0.848) and 0.842 (0.724-0.960), respectively. The combined model exhibited higher AUC values compared to other models. The decision curve analysis demonstrated that the combined model had superior clinical utility within the threshold probability range of 1% to 79% when compared to the other models. This study has successfully developed a predictive model that combines multiple features. The performance of the combined model is superior to that of single-feature models, allowing for early prediction of RIHT in patients with nasopharyngeal carcinoma after tomotherapy.

The influence of Gleason score ≤ 6 histology on the outcome of high-risk localized prostate cancer after modern radiotherapy.

We aimed to retrospectively review outcomes in patients with high-risk prostate cancer and a Gleason score ≤ 6 following modern radiotherapy. We analyzed the outcomes of 1374 patients who had undergone modern radiotherapy, comprising a high-risk low grade [HRLG] group (Gleason score ≤ 6; n = 94) and a high-risk high grade [HRHG] group (Gleason score ≥ 7, n = 1125). We included 955 patients who received brachytherapy with or without external beam radio-therapy (EBRT) and 264 who received modern EBRT (intensity-modulated radiotherapy [IMRT] or stereotactic body radiotherapy [SBRT]). At a median follow-up of 60 (2-177) months, actuarial 5-year biochemical failure-free survival rates were 97.8 and 91.8% (p = 0.017), respectively. The frequency of clinical failure in the HRLG group was less than that in the HRHG group (0% vs 5.4%, p = 0.012). The HRLG group had a better 5-year distant metastasis-free survival than the HRHG group (100% vs 96.0%, p = 0.035). As the HRLG group exhibited no clinical failure and better outcomes than the HRHG group, the HRLG group might potentially be classified as a lower-risk group.

Automatic IMRT treatment planning through fluence prediction and plan fine-tuning for nasopharyngeal carcinoma.

BACKGROUND: At present, the implementation of intensity-modulated radiation therapy (IMRT) treatment planning for geometrically complex nasopharyngeal carcinoma (NPC) through manual trial-and-error fashion presents challenges to the improvement of planning efficiency and the obtaining of high-consistency plan quality. This paper aims to propose an automatic IMRT plan generation method through fluence prediction and further plan fine-tuning for patients with NPC and evaluates the planning efficiency and plan quality. METHODS: A total of 38 patients with NPC treated with nine-beam IMRT were enrolled in this study and automatically re-planned with the proposed method. A trained deep learning model was employed to generate static field fluence maps for each patient with 3D computed tomography images and structure contours as input. Automatic IMRT treatment planning was achieved by using its generated dose with slight tightening for further plan fine-tuning. Lastly, the plan quality was compared between automatic plans and clinical plans. RESULTS: The average time for automatic plan generation was less than 4 min, including fluence maps prediction with a python script and automated plan tuning with a C# script. Compared with clinical plans, automatic plans showed better conformity and homogeneity for planning target volumes (PTVs) except for the conformity of PTV-1. Meanwhile, the dosimetric metrics for most organs at risk (OARs) were ameliorated in the automatic plan, especially Dmax of the brainstem and spinal cord, and Dmean of the left and right parotid glands significantly decreased (P < 0.05). CONCLUSION: We have successfully implemented an automatic IMRT plan generation method for patients with NPC. This method shows high planning efficiency and comparable or superior plan quality than clinical plans. The qualitative results before and after the plan fine-tuning indicates that further optimization using dose objectives generated by predicted fluence maps is crucial to obtain high-quality automatic plans.

Comparative dosimetric, setup margin, and treatment time analysis between ring gantry and C-Arm linear accelerators for VMAT-based craniospinal irradiation plans.

PURPOSE: The purpose of this study is to evaluate the dosimetric and treatment delivery characteristics of volumetric modulated arc therapy technique (VMAT)-based craniospinal axis irradiation (CSI) between ring gantry Halcyon (HAL) and C-arm based Novalis Tx (NTx) linear accelerator. Set-up margin and treatment delivery time for both machines were also taken into account. MATERIALS AND METHODS: Fifteen patients, 4 females and 11 males treated between March 2019 and February 2022 within the age group 4-56 years simulated in the supine position and were planned for multiple isocentre VMAT technique in ring gantry Halcyon and C-Arm Novalis linear accelerator for 6FFF and 6 MV flatten beam energy. The number of isocenters was the same in both the machines, usually three for adult adolescent age group patients and two for pediatric patients. Total on-couch time and the patient positional shift were captured for each isocenter during each session of treatment. Margins were calculated using Herk's formula of margin = 2.5Σ +0.7σ. Dosimetry, on-couch time, and set-up margin were compared between two competing arms. RESULTS: Ninety-five percent of PTV coverage (P = 0.333), volume receiving 107% (P = 0.676), total MU (P = 0.818) in both the arms were comparable and statically insignificant. Low-dose spillage such as D20% (P = 0.212) and D50% (P = 0.008) was lesser in HAL comparable to NTx. CI and HI were statically insignificant. Out of 26 organs at risk (OAR), only 3 organs showed a statically significant dose difference. The mean and maximum setup margin in any linear direction was 0.45 and 0.53 cm for HAL and 0.37 and 0.56 cm for NTx and, variation was statistically insignificant (0.23 < P < 0.47). On-couch time was 4.0 ± 5.5 min lesser for HAL and the difference in on-couch time between the two arms was statistically different. CONCLUSION: Even though the majority of the delivery parameters such as gantry speed, dose rate, beam characteristic (flatten or unflatten), MLC width, and speed between the ring gantry HAL and C-arm NTx linear accelerators were distinctly different, they offered no or minimal difference in the dose distribution and in the setup margin. HAL gives a faster treatment time delivery, which could be crucial for some selective cases such as patients receiving treatment under general anesthesia.

Dosimetric comparison between carotid-sparing IMRT and 3DCRT in early glottic cancer patients treated with definitive radiation therapy.

BACKGROUND: The purpose of this study was to evaluate the dosimetric benefits of carotid-sparing IMRT (intensity-modulated radiation therapy) over 3DCRT (three-dimensional conformal radiation therapy) in early glottic cancer patients. MATERIAL AND METHODS: Ten patients with histologically proven early-stage squamous cell cancer of glottis (T1N0), treated with definitive radiotherapy, were selected retrospectively for the dosimetric analysis. Patients were originally treated with 3DCRT technique. For comparison purpose, IMRT plans were generated for each patient. Dosimetric comparison was done between two techniques (IMRT and 3DCRT) in terms of PTV (planning target volume) coverage, HI (homogeneity index), CI (conformity index), and doses to right carotid artery, left carotid artery, and spinal cord. RESULTS: V95% for the PTV was higher in IMRT plans (98.26%) as compared to 3DCRT plans (95.12%) (P-value <0.001), whereas V105% for PTV was significantly higher in 3DCRT plans (16.77%) as compared to IMRT plans (0.32%) (P-value 0.11). In terms of both HI and CI, IMRT plans showed better conformity as compared to 3DCRT plans, with statistically significant difference. Both right and left carotid arteries' average mean and maximum doses were significantly lower in IMRT plans as compared to 3DCRT plans (P-value <0.001). IMRT plans resulted in significant carotid-sparing as compared to 3DCRT plans in terms of V35 and V50 (P-value <0.001). CONCLUSION: Carotid-sparing IMRT resulted in better PTV coverage and lower carotid artery dose as compared to 3DCRT in early glottic cancer patients.

Primary and adjuvant intensity-modulated radiotherapy in oropharyngeal carcinoma patients from a single institution.

BACKGROUND: To retrospectively access outcome, adverse events and prognostic factors in oropharyngeal carcinoma (OPC) patients treated with intensity-modulated radiotherapy (IMRT). METHODS: Ninety-eight OPC patients were treated between 2000 and 2015. Thirty-three patients received definitive and 65 adjuvant radiotherapy. Seventy-one percent had simultaneous chemotherapy. Patients were systematically followed up (mean 114 months, range 19-197 months). Statistical analysis used Kaplan-Meier method, Cox regression analysis, and log-rank test. Adverse events were classified according to common toxicity criteria version (CTCAE) 4.03. RESULTS: The 1-, 5-, and 10-year overall survival rates in the adjuvant vs. definitive cohort were 90.8% vs. 66.7%, 67.4% vs. 33.1%, and 57.7% vs. 16.5%. Survival in the adjuvant cohort was significantly longer than in the definitive cohort (P < 0.00005). Patients <65 years had a significantly longer survival than older patients. Locoregional tumor control rates after 1-, 5-, and 10 years in the adjuvant vs. definitive cohort were 90.2% vs. 66.7%, 82.2% vs 45.4%, and 72.1% vs. 30.3%. Locoregional tumor control in the adjuvant cohort was significantly longer than in the definite cohort (P < 0.005). Distant metastases were diagnosed in 20.4% of all patients. Most patients had mild CTCAE grade 1 and 2 adverse events and mild late adverse events including xerostomia, dysphagia, and lymphedema. CONCLUSION: Intensity-modulated radiotherapy for OPC is an important part of the treatment algorithm alone and in particular after surgery while the additional benefits of chemotherapy might be age dependent. Despite advanced tumor stages, nearly half of our patients were alive in the long term. The majority of patients had relatively mild chronic adverse events.

Efficacy of the collapsed cone algorithm calculated radiotherapy plans in intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT): A comparative dosimetric study in tumors of thorax.

AIM: In this study, efficacy of collapsed cone algorithm-generated intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) were evaluated for treatment of thoracic esophageal cancer. MATERIALS AND METHODS: Ten previously treated patients with VMAT were considered for evaluation. The planning parameters were evaluated in terms of max dose, mean dose, Homogeneity Index, Conformity Index for planning target volume, and organ at risk doses. Total monitor unit, treatment time, and gamma passing index were also reported. RESULTS: The target dose coverage of the VMAT and IMRT plans achieved the clinical dosimetric criteria for all ten patients in the evaluation. Under the condition of equivalent target dose distribution, the VMAT plan's Conformity Index, monitor unit, treatment time, and gamma passing index rate were superior than in the IMRT plan, and the result was statistically significant. CONCLUSION: Collapsed cone algorithm-based VMAT can have a more effective and better approach for esophageal cancer than IMRT.

Evaluating the relationship between contouring variability and modelled treatment outcome for prostate bed radiotherapy.

Objectives.Contouring similarity metrics are often used in studies of inter-observer variation and automatic segmentation but do not provide an assessment of clinical impact. This study focused on post-prostatectomy radiotherapy and aimed to (1) identify if there is a relationship between variations in commonly used contouring similarity metrics and resulting dosimetry and (2) identify the variation in clinical target volume (CTV) contouring that significantly impacts dosimetry.Approach.The study retrospectively analysed CT scans of 10 patients from the TROG 08.03 RAVES trial. The CTV, rectum, and bladder were contoured independently by three experienced observers. Using these contours reference simultaneous truth and performance level estimation (STAPLE) volumes were established. Additional CTVs were generated using an atlas algorithm based on a single benchmark case with 42 manual contours. Volumetric-modulated arc therapy (VMAT) treatment plans were generated for the observer, atlas, and reference volumes. The dosimetry was evaluated using radiobiological metrics. Correlations between contouring similarity and dosimetry metrics were calculated using Spearman coefficient (Γ). To access impact of variations in planning target volume (PTV) margin, the STAPLE PTV was uniformly contracted and expanded, with plans created for each PTV volume. STAPLE dose-volume histograms (DVHs) were exported for plans generated based on the contracted/expanded volumes, and dose-volume metrics assessed.Mainresults. The study found no strong correlations between the considered similarity metrics and modelled outcomes. Moderate correlations (0.5 <Γ< 0.7) were observed for Dice similarity coefficient, Jaccard, and mean distance to agreement metrics and rectum toxicities. The observations of this study indicate a tendency for variations in CTV contraction/expansion below 5 mm to result in minor dosimetric impacts.Significance. Contouring similarity metrics must be used with caution when interpreting them as indicators of treatment plan variation. For post-prostatectomy VMAT patients, this work showed variations in contours with an expansion/contraction of less than 5 mm did not lead to notable dosimetric differences, this should be explored in a larger dataset to assess generalisability.

Radiotherapy for breast cancer.

In early breast cancer, adjuvant moderately hypofractionated regimens are recommended for both whole breast, partial breast and locoregional irradiation which abbreviates the overall treatment time, as argued in this review. Gating is recommended as well as the use of a simultaneous integrated boost when indicated. A tangential field set-up is standard, however, for challenging cases volumetric modulated arc therapy techniques, or referral for proton therapy, may be considered. In the metastatic setting, stereotactic radiotherapy is a promising treatment option for oligometastatic disease.