Intensity-modulated Radiotherapy Technique Research Articles

Analysis of patients with parotid recurrence after parotid-sparing IMRT for nasopharyngeal carcinoma: case series and review of the literature.

Intensity-modulated radiotherapy (IMRT) is the standard treatment approach for nasopharyngeal cancer (NPC). IMRT enables effective sparing of the parotid glands and reduces the risk of xerostomia, acommon complication of head and neck irradiation. Nevertheless, it is essential to determine whether the parotid-sparing IMRT (ps-IMRT) technique yields increased intra-/periparotid recurrence rates, which constitutes the main purpose of this study. Patients with adiagnosis of NPC that received definitive chemoradiotherapy/radiotherapy (CRT/RT) between 1991 and 2021 were evaluated retrospectively. Patients with intra-/periparotid recurrence were detected and prognostic factors for recurrence were sought. Atotal of 746 patients were evaluated. Two-dimensional (2D)-RT was applied to 541, 3D conformal RT (3D-CRT) to 10, and ps-IMRT to 195 patients. After amedian 85-month follow-up, one (0.18%) patient who received 2D-RT and four (2%) patients who received ps-IMRT experienced an intra-/periparotid recurrence. The median time to intra-/periparotid recurrence was 11.9 months. All patients had been diagnosed with ametastatic lymph node > 2 cm at levelII of the ipsilateral neck. In addition, all recurrences occurred on the same side as the positive neck at the time of diagnosis. The 3‑year overall survival, locoregional recurrence-free survival, and distant metastasis-free survival rates were 80%, 40%, and 60%, respectively. Intra-/periparotid recurrence is extremely rare in NPC. However, it is still possible to identify and characterize particular risk factors, which include ametastatic lymph node at levelII, particularly > 2 cm, and multinodal disease at the time of diagnosis.

An efficacy of protection the organs at risks comparison between the intensitymodulated radiotherapy therapy (IMRT) and the three-dimensional conformal radiotherapy (3DCRT).

To compare the efficiency of three-dimensional conformal radiotherapy and intensity-modulated radiation therapy techniques. The cross-sectional study was conducted from February to August 2021 at Al-Amal National Hospital, Baghdad, Iraq, and comprised patients aged 19-45 years with cancerous head and neck tumours of size 2-7cm. All the patients underwent magnetic resonance imaging or computed tomography simulation scans. Treatment planning techniques used for each patient were three-dimensional conformal radiotherapy and intensitymodulated radiotherapy. After evaluating patterns, a better plan and treatment with an X-ray beam was chosen. Data was analysed using SPSS 24. The study involved thirty participants, with 17(57%) females and 13(43%) males, aged 19-45, and 28 patients having chemotherapy. Six out of thirty had craniotomy surgery. The intensity-modulated radiation therapy had a safer radiation dose than the three-dimensional conformal radiotherapy for spinal cord (p=0.3203), brain stem (p= 0.17924), right parotid gland (p=0.8556) and left parotid gland (p=0.2193). The three-dimensional conformal radiotherapy protected the organs better than intensity-modulated radiation therapy for left optic nerve (p=0.1227), right optic nerve (p=0.0032), left eye (p=0.3859), right eye (p=0.1189), left lens (p=0.0004), right lens (p=0.0001), optic chiasm (p=0.0320) and pituitary gland (p=0.9162). The intensity-modulated radiation therapy technique protected the spinal cord, brain stem, and right and left parotid glands. The three-dimensional conformal radiotherapy was safe for left and right optic nerves, left and right eyes, left and right lenses, optic chiasm and pituitary glands.

Intensity-modulated radiotherapy (IMRT) versus three-dimensional conformal radiotherapy (3DCRT) as treatment plans for head and neck tumours.

To compare intensity-modulated radiation therapy with three-dimensional conformal radiation therapy 3DCRTwith respect to dose coverage for target volume. The cross-sectional study was conducted at Al-Amal National Hospital, Baghdad, Iraq, from November 2020 to March 2021 and comprised patients with head and neck cancerous tumours. The patients underwent computed tomography scans, and were subsequently subjected to three-dimensional conformal radiotherapy and intensity-modulated radiotherapy treatment planning techniques on the basis of Monaco 5.1. The oncologist selected the better plan depending on evaluation parameters for each patient who was then irradiated with X-ray treatment. Data was analysed using SPSS 24. There were 30 patients, 17 (57%) females and 13 (43%) males with the age range of 19-45 years. Of the total, 28 received chemotherapy and 6 patients underwent brain surgery. The intensity-modulated radiation therapy resulted in significant coverage of the tumour than the three-dimensional conformal radiation therapy in phase 1 (p<0.00001) and phase II (p=0.0023). The intensity-modulated radiation therapy technique achieved a lower homogeneity value (p=0.0004) and higher conformity value (p<0.00001) than three-dimensional conformal radiation therapy. In phase II, no significant homogeneity index was found between the two therapies (p=0.072). The intensity-modulated radiation therapy showed significantly better conformity compared to three-dimensional conformal radiation therapy (p<0.00001). The intensity-modulated radiation therapy significantly improved coverage, plan conformity, and humongous dose distribution for head and neck tumours compared to the three-dimensional conformal radiation therapy 3DCRT.

Evaluation of Inverse Planned and Forward Planned Intensity Modulated Radiotherapy Techniques in Breast Cancer

Introduction: The objective of this study is to compare the dosimetric parameters of radiation to the whole breast between the two intensity-modulated radiotherapy (IP IMRT) techniques, i.e. Inverse planned IMRT (IP IMRT) and Forward Planned IMRT (FP IMRT) with regard to target coverage (PTV) and irradiation of organs at risk (OAR). Material and Methods: Plain and Contrast enhanced computed tomography (CECT) datasets were created for 41 patients treated with whole breast radiation therapy. CT simulation and treatment is performed using deep inspiratory breath hold technique (DIBH). Radiotherapy treatment Planning is done using Eclipse Treatment Planning System (version 13.7) with a prescription dose of 40 Gy in 15#. The developed treatment plans were subjected to objective comparison of PTV and OARs using dose volume histograms (DVH). Results: IP IMRT plans provided better coverage (99.5% vs 97.6%), comparable though higher maximum dose (Dmax 45.0 VS 44.1 Gy), higher hot spot (PTV105% 49.2 vs 33), lower volumes receiving 20, 25, 30 Gy (V20, V25, V30) for heart, more homogeneous (homogeneity index 0.10 vs. 0.14) and conformal dose distribution (conformity Index 1.0 vs 0.98) compared to FP IMRT. Regarding OAR dosimetry it is observed that FP IMRT showed reduced mean dose to Coronary artery (LADCA), Contralateral Lung (CL), Contralateral breast (CB) along with reduction in low dose region (V5) to all OARs under study. It was also observed that Monitor units used and planning time were lower for FP IMRT. Conclusion: On weighing different dosimetric factors, both the techniques have displayed their own advantages and disadvantages. Choosing a planning technique needs to be customized taking into consideration various factors such as breast topography, size and volumes of breast, availability of expertise planning skills and resources.

COMPARATIVE RADIATION DOSIMETRY OF WHOLE BREAST RADIOTHERAPY USING IMRT AND VMAT TECHNIQUES IN LEFT SIDED BREAST CANCER PATIENTS AFTER BREAST CONSERVING SURGERY

Background:The radiotherapy of left sided breast cancers is mandatory and integral part of treatment and challenging because of surrounding critical structures posing increased risk of complications. The main objective of this study was to quantify doses toorgan at risk(OARs) including left lung, heart, contralateral breast, spinal cord, and planning target volume (PTV) using different radiation techniques like Intensity modulated radiation therapy (IMRT)&amp;volumetric modulated arc therapy (VMAT) and comparison of radiation dosimetry. Methods: A prospective study of 30 patients of left sided breast cancer who had undergone Breast Conservative Surgery (BCS) and chemotherapy was done for adjuvant radiation. For every patient radiation planning was done by two different techniques IMRT and VMAT. Then the comparison of radiation dosimetry parameters was done for all the techniques including the parameters like PTV coverage, doses to OAR like heart, left lung, contralateral breast and spinal cord and head of humerus. The Homogenity Index (HI) were calculated. Result: The Mean age of the patient was 46.7 years. When comparing the doses delivered in IMRT and VMAT Technique for left sided breast cancer post breast conservation surgery there was significant difference in PTV Breast and axilla V95 Gy. It was 96.2±1.9% (IMRT) vs 94.8±1.71% (VMAT), (p=0.004). However significant sparing of Organs at Risk was seen. With ipsilateral lung dose mean V5 Gy was 77.86± 9.68% (IMRT) v/s 83.04± 9.86 % (VMAT), (p=0.0446). Also mean V30 Gy was 14.6±4.82% with IMRT vs 16.54±5.86% with VMAT, (p=0.0169). Heart mean dose was 8.8±1.49 Gy with IMRT and 10.98±3.7 Gy with VMAT, (p=0.0227). Further V30 Gy for Heart was 4.61±3.8% with IMRT and 6.72±4.0% with VMAT, (p=0.0132).No significant difference was seen with IMRT and VMAT technique for contralateral lung, contralateral breast and spinal cord. Conclusion: In treatment of patients with radiation with left breast cancer patients post BCS using IMRT and VMAT technique it is seen significant dose reduction with IMRT Technique for ipsilateral lung and Heart as compared to VMAT technique. Significant V95 coverage for PTV Breast and axilla with IMRT as compared to VMAT. Hence in our Study IMRT technique was found to be superior for better sparing of Organ at risk and better PTV coverage.

Evaluation of the conformity of intensity-modulated radiation therapy and volumetric modulated arc therapy using AAPM TG 119 protocol.

The aim of this work was to evaluate the conformity of intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT), and verify the accuracy of the planning and delivery system used in this work based on the AAPM TG-119 protocol. The Eclipse 13.6 treatment planning system (TPS) was used to plan the TG-119 test suite, which included four test cases: MultiTarget, Prostate, Head/Neck, and C-Shape for IMRT and VMAT techniques with 6 MV and 10 MV acceleration voltages. The results were assessed and discussed in terms of the TG-119 protocol and the results of previous studies. In addition, point dose and planar dose measurements were done using a semiflex ion chamber and an electronic portal imaging device (EPID), respectively. The planned doses of all test cases met the criteria of the TG-119 protocol, except those for the spinal cord of the C-Shape hard case. There were no significant differences between the treatment planning doses and the doses given in the TG-119 report, with p-values ranging from 0.974 to 1 (p > 0.05). Doses to the target volumes were similar in the IMRT and VMAT plans, but the organs at risk (OARs) doses were different depending on the test case. The planning results showed that IMRT is more conformal than VMAT in certain cases. For the point dose measurements, the confidence limit (CLpoint) of 0.030 and 0.021 were better than the corresponding values of 0.045 and 0.047 given in the TG-119 report for high-dose and low-dose areas, respectively. Regarding the planar dose measurements, the CLplanar value of 0.38 obtained in this work was lower than that given in the TG-119 report (12.4). It is concluded that the dosimetry measurements performed in this study showed better confidence limits than those provided in the TG 119 report. IMRT remains more conformal in certain circumstances than the more progressive VMAT. When selecting the method of delivering a dose to the patient, several factors must be considered, including the radiotherapy technique, energy, treatment site, and tumour geometry.

Incorporating intensity modulated total body irradiation into a Children's Oncology Group trial: Rationale, techniques, and safeguards.

Historically, total body irradiation (TBI) has been delivered using static, parallel opposed photon beams (2D-TBI). Recently, centers have increasingly used intensity-modulated radiation therapy (IMRT) techniques for TBI. Relative to 2D-TBI, IMRT can reduce doses to critical organs (i.e., lungs and kidneys) while delivering myeloablative doses to the rest of the body, so it may decrease the risk of toxicity while maintaining oncologic outcomes. Despite these potential benefits, delivering TBI using IMRT introduces new challenges in treatment planning and delivery. We describe the extensive experience with IMRT-based TBI at Stanford University and City of Hope Cancer Center. These groups, and others, have reported favorable clinical outcomes and have developed methods to optimize treatment planning and delivery. A critical next step is to evaluate the broader adoption of this approach. Therefore, IMRT-based TBI will be incorporated into a prospective, multi-institutional Children's Oncology Group study with careful procedures and safeguards in place.

Dosimetric effect of collimator rotation on intensity modulated radiotherapy and volumetric modulated arc therapy for rectal cancer radiotherapy.

Intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) are the main radiotherapy techniques for treating and managing rectal cancer. Collimator rotation is one of the crucial parameters in radiotherapy planning, and its alteration can cause dosimetric variations. This study assessed the effect of collimator rotation on the dosimetric results of various IMRT and VMAT plans for rectal cancer. Computed tomography (CT) images of 20 male patients with rectal cancer were utilized for IMRT and VMAT treatment planning with various collimator angles. Nine different IMRT techniques (5, 7, and 9 coplanar fields with collimator angles of 0°, 45°, and 90°) and six different VMAT techniques (1 and 2 full coplanar arcs with collimator angles of 0°, 45°, and 90°) were planned for each patient. The dosimetric results of various treatment techniques for target tissue (conformity index [CI] and homogeneity index [HI]) and organs at risk (OARs) sparing (parameters obtained from OARs dose-volume histograms [DVH]) as well as radiobiological findings were analyzed and compared. The 7-fields IMRT technique demonstrated lower bladder doses (V40Gy, V45Gy), unaffected by collimator rotation. The 9-fields IMRT and 2-arcs VMAT (excluding the 90-degree collimator) had the lowest V35Gy and V45Gy. A 90-degree collimator rotation in 2-arcs VMAT significantly increased small bowel and bladder V45Gy, femoral head doses, and HI values. Radiobiologically, the 90-degree rotation had adverse effects on small bowel NTCP (normal tissue complication probability). No superiority was found for a 45-degree collimator rotation over 0 or 30 degrees in VMAT techniques. Collimator rotation had minimal impact on dosimetric parameters in IMRT planning but is significant in VMAT techniques. A 90-degree rotation in VMAT, particularly in a 2-full arc technique, adversely affects PTV homogeneity index, bladder dose, and small bowel NTCP. Other evaluated collimator angles did not significantly affect VMAT dosimetrical or radiobiological outcomes.

Radiation Dose prediction for Cervical Cancer Patients Using IMRT Technique with a Machine Learning Model Based on Support Vector Regression (SVR)

Cervical cancer poses significant global health challenges, necessitating innovative treatment approaches. This study explores the integration of Support Vector Regression (SVR) in predicting radiation doses for cervical cancer radiotherapy, aiming to enhance the precision of Intensity Modulated Radiation Therapy (IMRT). We developed and validated an SVR model using datasets of 102 and 173 cervical cancer cases to predict dose distributions based on radiomic and dosiomic features. Our methodology involved pre-processing, feature extraction, data normalization, and rigorous training and testing of the model. Results indicated that larger, more diverse datasets significantly improve predictive accuracy, with the model demonstrating robust performance metrics. Notably, the study highlights the critical role of dataset size over stage uniformity in model reliability. These findings underscore the potential of machine learning in refining radiotherapy planning, reducing the workload on medical physicists, and improving patient outcomes. Future research should focus on expanding dataset sizes and enhancing model precision, particularly for challenging anatomical regions. This study paves the way for more personalized and effective radiotherapy planning, benefiting both clinicians and patients.

Artificial Intelligence Assistive Tool for Radiotherapy Plan Evaluation Based on Analysis of Integral Dose

ABSTRACT Aim: The aim of the present study is to propose an in-house developed artificial intelligence (AI) tool based on Python programming for the purpose of integral doses (IDs) calculation useful in plan evaluation in modern radiotherapy techniques. Materials and Methods: Retrospectively, curative radiotherapy plans of cancer head and neck planned with intensity-modulated radiation therapy techniques employing seven and nine photon beams of 6 MV, were included in this study. The derived dose-volume histogram data were analyzed for the calculation of ID for each of the contoured structures including high-risk planning target volume (HR-PTV) and surrounding normal structures using an in-house developed Python program. Results: In this study, variation of ID between nine-beam and seven-beam plans was calculated. It was found that the ID for HR-PTV volume was almost equal in both nine and seven beam plans with the percentage variation range 0.4%–1.4%, however, significant variation up to 14.4% in the ID of organ at risk was found. Furthermore, we utilized the standard deviation (SD) as a metric to assess the variability of the ID within the PTV and the surrounding normal tissues. The HR-PTV exhibited a low SD of 0.71, suggesting consistent ID patterns. In contrast, the organs at risk (OAR) exhibited noteworthy variations in SD values, with some reaching as high as 16.75. The SD was relatively elevated in the OAR in comparison to the HR-PTV. These elevated SD values within the OAR indicate significant dose variability across different patients. Conclusion: It is found that ID increases as the number of beams increases. The Python program used in this study for the calculation of ID, as an AI assistive tool for plan evaluation, can be run on the TPS or on a side-by-side computer which may be helpful in finalizing radiotherapy plans.

Effect of bilateral superficial parotid gland sparing IMRT on xerostomia and QOL: A prospective study

ABSTRACT Background: Superficial lobe constitutes 80% of the parotid and is situated lateral to mandible and can be better spared during intensity modulated radiation therapy (IMRT) for head and neck cancer (HNC). This study aimed to see the impact of bilateral superficial parotid gland (PG) sparing IMRT on xerostomia and quality of life (QOL) in patients with HNC receiving radiation. Study Design: Prospective, questionnaire-based study. Materials and Methods: Thirty-four patients with histopathologically proven non-nasopharyngeal non-oral cavity HNC were included in this study. IMRT technique was used and a constraint of 24 Gy was given to combined superficial PG. Physician- and patient-rated xerostomia and QOL scores were recorded at baseline and two weeks, three months, and six months post-radiation therapy (RT). The combined superficial PG dose correlated with xerostomia and QOL scores. Results: The combined superficial PG and combined whole PG mean dose was 18.71 Gy and 30 Gy, respectively, and the difference was statistically significant (P-&lt; 0.001). At two weeks, three months, and six months post-RT, the odds of xerostomia scores were 0.11, 0.071, 0.042, respectively for a median dose of &lt;18 Gy compared to &gt;18 Gy and was statistically significant P=(0.001). Conclusion: Bilateral superficial PG sparing IMRT is beneficial in reducing xerostomia and translates to a better QOL.

Evaluation of Normal Tissue Objective Function for Treatment Planning of Solitary Brain Metastasis Using Intensity-modulated Radiosurgery Techniques.

The purpose of this study was to systematically examine the normal tissue objective (NTO) function by comparing its variations for planning solitary brain metastasis with intensity-modulated and volumetric-modulated arc radiosurgery techniques. Twenty-two cases were retrospectively planned with two NTO parameter sets named A and B using intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) techniques. The Type A set used slope, k = 0.4 mm-1 plus end dose, De = 20%, whereas the Type B set used k = 1.0 mm-1 plus De = 10%. The resulting four plan types were assessed using mean dose to 5 mm exterior ring, normal brain receiving 12 Gy (V12), 5 Gy total brain dose volume (V5), gradient index (R50%), focal index (FI), Paddick conformity index (PCI), prescription isodose surface (PIDS), and MU/Gy. Brain doses were significantly lower for VMAT than for IMRT. R50% was more favorable for VMAT than for IMRT for each planning target volume (PTV). The mean FI was comparable between the corresponding IMRT and VMAT plan types. PCI was better for the IMRT_A plan type. PIDS was significantly lower for Type B plans than Type A for both techniques. For PTVs <3 cm3, IMRT plans showed poor dosimetry and required NTO settings stricter than Type B. The application of NTO variations demonstrated varied dosimetry for IMRT and VMAT techniques. The NTO parameter variations produced field size and/or beamlet size/shape variations. The strict NTO parameter set generated more conformal beam apertures to reduce the brain dose. VMAT plan types showed significantly lower brain doses and better dosimetry for all target sizes.

Efficacy and Toxicity of (Chemo)Radiation Therapy in HIV+ Patients with Squamous Cell Anal Cancer, a Subgroup Analysis of the National Multicenter Cohort FFCD-ANABASE

The influence of human immunodeficiency virus (HIV) infection on clinical outcomes in patients receiving (chemo)radiation therapy (RT) for squamous cell carcinoma of the anus (SCCA) is debated. The objective of this study was to compare efficacy and safety according to HIV status in patients with SCCA treated with C/RT. Between January 2015 and April 2020, 488 patients with a known HIV status (17.6% HIV+) were treated with radiation therapy for SCCA and included in the FFCD-ANABASE multicentric prospective cohort. Clinical outcomes including overall survival (OS), locoregional recurrence-free survival, colostomy-free survival, response rate at 4 to 6 months, cancer-specific survival, relapse-free survival, and severe acute and late toxicity were compared between HIV+ and HIV- patients. The median follow-up was 35.8 months. HIV+ patients were younger (P < .01) and predominantly male (P < .01). Intensity modulated radiation therapy was performed in 80.7% of patients, and 80.9% received concurrent chemotherapy. A higher proportion of HIV+ patients received induction chemotherapy compared with HIV- patients. No statistically significant difference in overall treatment time or severe acute and late toxicities was found between HIV+ and HIV- patients. In univariate analyses, OS (HR = 2.1 [CI 95% 1.2;3.5], P = .007), locoregional recurrence-free survival (HR = 1.7 [1.1;2.7], P = .02), and colostomy-free survival (HR = 1.7 [1.1;2.6], P = .01) were significantly shorter in HIV+ patients than in HIV- patients. Response rate, cancer-specific survival, and relapse-free survival were not significantly different. The recurrence site was significantly different according to HIV status. In the multivariate analysis, prognostic factors for OS were a World Health Organization performance status of ≥1 for the whole population, as well as HIV+ status for the subgroup of women. HIV+ patients treated with chemo-RT for SCCA have poorer clinical outcomes, especially women. No difference was found in toxicity according to HIV status with intensity modulated radiation therapy technique.

Modulated Arc Therapy for hippocampal-avoidance whole brain radiation therapy: planning comparison with intensity modulated Radiation Therapy.

This study aimed to evaluate the modulated arc therapy (mARC) technique as a planning and treatment option for hippocampal sparing whole brain radiotherapy (HS-WBRT) following the Radiation Therapy Oncology Group (RTOG) 0933 dosimetric criteria. Computed tomography (CT) and magnetic resonance imaging (MRI) were selected retrospectively for 15 patients. Two types of plans were created for each patient, namely an intensity-modulated radiation therapy (IMRT) and a mARC plan. IMRT and mARC plans were compared in terms of plan quality indices, absorbed dose to organs at risk (OARs), number of monitor units (MUs), and treatment time. All plans in both techniques were considered clinically acceptable for treatment. However, IMRT plans presented a higher conformity (p = 0.01) as well as a higher homogeneity as compared to mARC plans, but this difference was not statistically significant (p > 0.05). In terms of the preservation of the hippocampus, it was observed that the IMRT plans achieved significantly lower doses for both 100% of its volume and for its maximum dose (p < 0.001). The evaluation of the remaining OARs showed that the IMRT technique resulted in lower doses, and significant differences were observed for the following organs: left cochlea (p < 0.001), left eye (p < 0.001), right eye (p = 0.03), both lenses of the eye (p < 0.001), and right optic nerve (p = 0.02). Despite these differences, the absolute differences in all dosimetric parameters were low enough to bear any clinical relevance. A drastic (close to 65%) and significant (p < 0.001) decrease was observed in the number of MUs for the mARC plans. This resulted in a substantial decrease in treatment time (60.45%, p < 0.001). It is concluded that the mARC technique is a feasible planning and treatment solution for HS-WBRT that meets the RTOG 0933 criteria. The main advantage of using mARC over IMRT for HS-WBRT is the considerable reduction in MUs and treatment time.

Hybrid Treatment Planning for Chest Wall Irradiation Utilizing Three-Dimensional Conformal Radiotherapy (3DCRT), Intensity-Modulated Radiation Therapy (IMRT), and Volumetric Modulated Arc Therapy (VMAT): A Systematic Review.

Novel hybrid approaches for chest wall irradiation show promising outcomes regarding target coverage and sparing organs at risk (OARs). In this systematic review, we compared hybrid volumetric modulated arc therapy (H-VMAT) or hybrid intensity-modulated radiotherapy (H-IMRT) techniques with non-hybrid techniques, such as three-dimensional conformal radiation therapy (3DCRT), field-in-field (FIF), intensity-modulated arc therapy (IMRT), and volumetric modulated arc therapy (VMAT), for breast cancer patients with mastectomy. Our focus was the plan quality and dose distribution to the OARs. Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist, we performed a systematic review and quality appraisal of primary studies evaluating hybrid therapy to the chest wall and the OARs. An extensive online search of PubMed and Scopus databases was conducted using appropriate keywords. The dose to the OARs (lung, heart, and contralateral breast), planning target volume (PTV), homogeneity index (HI), and conformity index (CI) were extracted. The data were then tabulated and compared for the outcomes between modalities among the studies.Nine studies that met the search criteria were selected to evaluate the PTV coverage and dosimetric results of hybrid and non-hybrid techniques. In terms of 95% PTV coverage, among nine reviewed studies, the largest difference between the two techniques was between VMAT (47.6 Gy) and H-VMAT (48.4 Gy); for the conformity index, the largest difference was noted between 3DCRT (0.58) and H-VMAT (0.79). In both cases, differences were statistically significant (P < 0.005). Two studies showed dose homogeneity improvement within the treatment target in H-VMAT (0.15 and 0.07) compared with 3DCRT (0.41 and 0.12), with a P value of <0.001. Two studies did not report on the homogeneity index, and three others observed no statistical difference. Regarding OARs, in the comparison of H-VMAT and VMAT, the largest significant change was in the volume receiving 5 Gy (V5Gy) of the ipsilateral lung and the V10Gy of the contralateral lung. For the ipsilateral lung, V5Gy was 90.7% with VMAT versus 51.45% with H-VMAT. For the contralateral lung, V10Gy was 54.9% with VMAT versus 50.5% with H-VMAT. In six studies, the mean dose of the contralateral breast was lower in hybrid techniques than in single modalities: VMAT (4.2%, 6.0%, 1.9%, 7.1%, 4.57%) versus H-VMAT (1.4%, 3.4%, 1.8%, 3.5%, 2.34%)and IMRT (9.1%) versus H-IMRT (4.69%). Although most studies did not report on monitor units and treatment time, those that included them showed that hybrids had lower monitor units and shorter treatment times.Hybridtechniques in radiotherapy, such as combining two modalities, can indeed facilitate lower doses to OARsfor patients with a high risk of toxicities. Prospective clinical studies are needed to determine the outcomes of breast cancer treated with hybrid techniques.

Impact of Radiation on Dysphagia-Related Structures: A Dosimetric and Clinical Comparative Analysis of Three-Dimensional Conformal Radiotherapy (3D-CRT) and Intensity-Modulated Radiation Therapy (IMRT) Techniques in Patients With Head and Neck Cancer.

Introduction Head and neck squamous cell carcinoma (HNSCC)is a significant health concern in India, with around one million new cases annually. The prevalence of HNSCC is notably high in Asia, especially in India, due to habitslike tobacco chewing, betel nut usage, and alcohol consumption. Treatment typically involves a combination of surgery, radiation, chemotherapy, and biological therapy, aiming for tumor control while preserving function and quality of life. However, survivors often face long-term side effectslike difficulty swallowing, leading to complicationssuch as aspiration pneumonia. Intensity-modulated radiotherapy (IMRT) has shown promise in improving outcomes by sparing critical swallowing structures. Efforts to minimize radiation-related dysphagia are crucial for enhancing patients' quality of life post-treatment. Our study focuses on examining dosimetric parameters associated with dysphagia aspiration, alongside evaluating dysphagia grades in both treatment groups using the RTOGscale. Material and methods Patients with histologically confirmed non-metastatic head and neck carcinomas were included in our study in November 2018-April 2020. A total of 56 patients were taken into our study with 28 in each arm. They underwent radical radiotherapy (RT) with a total dose of 66-70 Gy, with or without concurrent chemotherapy, meeting specific inclusion criteria and excluding those receiving reirradiation or with distant metastasis. Patients were divided into two groups: Group I received three-dimensional conformal radiotherapy (3D-CRT), and Group II received IMRT. Treatment planning involved immobilization, CT imaging, delineation of target volumes and organs at risk, and contouring of swallowing structures. Dose-volume histogram parameters (mean dose, maximum dose, V30, V70, V80, D50, and D80) were used to assess mean dose to swallowing structures outside the planning target volume (PTV), with a mean dose constraint of 50 Gy. Dysphagia was evaluated using the RTOGcriteria at baseline, during treatment, and six months post-treatment. Statistical analysis was performed using SPSS, with significance set at p < 0.05. Results In our study, the mean age at presentation differed slightly between the IMRT and 3D-CRT arms: 58 years versus 55 years, respectively. A higher proportion of patients in both arms experienced symptoms for three to six months, with 53.6% in 3D-CRT and 42.9% in IMRT. Stage distribution varied, with IV being most common in 3D-CRT and stage II in IMRT. Approximately 56% of patients in both groups had a history of smoking. Significant differences were observed in spinal cord dose between 3DCRT and IMRT techniques (p < 0.001). Similarly, a significant difference was found in the mean dose received by dysphagia aspiration-related structures (DARSs) between the 3D-CRT and IMRT arms (p = 0.04). Patients in the IMRT arm exhibited superior dysphagia grades compared to those in the 3D-CRT arm, with statistical significance observed in the third month (p = 0.008) and sixth month (p = 0.048). Conclusion Our study found a notable decrease in the mean DARS dose and reduced dysphagia severity at three and six months in the IMRT group compared to the 3D-CRT group. However, due to the diverse study population, establishing a definitive correlation between the DARS dose and dysphagia severity was challenging. Future large-scale studies are needed to validate these findings for improved preservation of DARS structures.

A Randomised Phase II Trial to Evaluate the Feasibility of Radiotherapy Dose Escalation, Facilitated by Intensity-Modulated Arc Radiotherapy Techniques, in High-Risk Neuroblastoma

BACKGROUND AND PURPOSEFor high-risk neuroblastoma, planning target volume coverage is often compromised to respect adjacent kidney tolerance. This trial investigated whether intensity-modulated arc radiotherapy techniques (IMAT) could facilitate dose escalation better than conventional techniques. MATERIALS AND METHODSChildren with high-risk abdominal neuroblastoma referred for radiotherapy to the primary tumour site and involved regional lymph nodes were randomised to receive either standard dose (21 Gy in 14 fractions) or escalated dose (36 Gy in 24 fractions) radiotherapy. Dual planning with both a conventional anterior-posterior parallel opposed pair radiotherapy technique and an IMAT technique was performed. The quality of target volume and organ-at-risk delineation, and dosimetric plans, were externally reviewed. Dosimetric parameters were used to judge the superior technique for treatment. This feasibility trial was not powered to detect improvement in outcome with dose escalation. RESULTSBetween 2017 and 2020, 50 patients were randomised and dual-planned. The IMAT technique was judged more favourable in 48 patients. In all patients randomised to receive 36 Gy, IMAT would have permitted delivery of the full dose (median D50% 36.0 Gy, inter-quartile range 36.0–36.1 Gy) to the target volume, whereas dose compromise would have been required with conventional planning (median D50% 35.6 Gy, inter-quartile range 28.7–35.9 Gy). CONCLUSIONIMAT facilitates safe dose escalation to 36 Gy in patients receiving radiotherapy for neuroblastoma. The value of dose escalation is now being evaluated in a current prospective phase III randomised trial.

DOSIMETRIC COMPARISON OF INTENSITY-MODULATED RADIATION THERAPY (IMRT) AND VOLUMETRIC-MODULATED ARC THERAPY (VMAT) IN RECTAL CANCER PATIENTS: A COMPREHENSIVE ANALYSIS

This study aimed to conduct a thorough dosimetric comparison between two advanced radiotherapy techniques, Intensity-Modulated Radiation Therapy (IMRT) and Volumetric-Modulated Arc Therapy (VMAT), to ascertain the superior modality in terms of dose distribution and organ-at-risk sparing for rectal cancer patients. Thirty-three patients with ECOG performance status 1, aged between 18 to 60 years, diagnosed with Stage II to III rectal cancer, were included in this prospective study. Each patient underwent treatment planning with IMRT and VMAT techniques using Varian system simulation computed tomography scans. The dosimetric analysis encompassed the evaluation of target volume dose homogeneity, conformity, and doses to at-risk organs. The dosimetric comparison was conducted utilizing seven-field IMRT and dual arc VMAT plans. Statistical analysis was performed using paired t-tests and SPSS 20 software. Treatment plan constraints adhered to the RTOG 9406 guidelines, ensuring adequate planning target volume (PTV) coverage, homogeneity index, conformity index, and dose limits for organs at risk, including small bowel V20 (&lt;200cc), bladder V45 (&lt;21Gy), and femoral head V50 (≤30 Gy). Volumetric arc therapy plans demonstrated superior dose homogeneity to fixed-field intensity-modulated plans (p-value = 0.04), particularly in femoral head dose-limiting toxicity (p-value = 0.00). However, intensity-modulated therapy exhibited equivalent or superior performance in other evaluated parameters. Our findings suggest that while VMAT offers advantages in PTV coverage homogeneity and femoral head dose-limiting toxicity, IMRT remains competitive and potentially preferable in certain dosimetric aspects. The choice between IMRT and VMAT should be carefully considered based on individual patient characteristics and treatment goals. This comprehensive dosimetric comparison contributes valuable insights into optimizing radiotherapy planning for rectal cancer patients, potentially guiding clinical decision-making and improving treatment outcomes.

Measurement and Incorporation of Laryngeal Motion Using cine-MRI on an MR-Linear Accelerator to Generate Radiation Therapy Plans for Early-stage Squamous Cell Cancers of the Glottis

IntroductionSwallow-related motion of the larynx is most significant in the cranio-caudal directions and of short duration. Conventional target definition for radical radiotherapy includes coverage of the whole larynx. This study longitudinally examined respiration- and swallow-related laryngeal motions using cine-MRI. We further analysed the dosimetry to organs at risk by comparing 3D-conformal radiotherapy (3D-CRT), Volumetric-Modulated Arc Therapy (VMAT) and Intensity-Modulated Radiotherapy (IMRT) techniques. MethodsFifteen patients with T1-2 N0 glottic squamous cell carcinomas were prospectively recruited for up to three cine-MRI scans on the Elekta Unity MR-Linear accelerator, at the beginning, middle and end of a course of radical radiotherapy. Swallow frequency and motion of the hyoid bone, cricoid and thyroid cartilages and vocal cords were recorded during swallow and rest. Adapted treatment volumes consisted of GTV + 0.5-1 cm to a CTV with an additional ITV for personalised resting-motion. Swallow-related motion was deemed infrequent and was not accounted for in the ITV. We compared radiotherapy plans for 3D-CRT (whole larynx), VMAT (whole larynx), VMAT and IMRT (ITV for resting motion). ResultsResting- and swallow- motions were most prominent in the craniocaudal plane. There were no significant changes in the magnitudes of motions over the course of radiotherapy. There was a trend for a progressive reduction in the frequency of swallow. Treatment of partial-larynx volumes with intensity-modulated methods significantly reduced the dose to carotid arteries compared to whole-larynx. Robustness analysis demonstrated that when accounting for intra-fraction swallow, the total dose delivered to the ITV/PTV was maintained above 95%. ConclusionsSwallow-related motions are infrequent and accounting for resting motion in an ITV is sufficient. VMAT/IMRT techniques that treat more conformal targets can significantly spare critical organs at risk such as the carotid arteries and thyroid gland, potentially reducing the risk of carotid artery stenosis related and other complications long-term.

Investigation of the effect of bolus on skin dose in breast cancer treatment with tomotherapy and LINAC radiotherapy devices

In postmastectomy radiation therapy (PMRT), it is important that the chest wall skin is included in the target volume and receives an adequate dose. This study aims to investigate the effect of bolus on skin dose in breast cancer treatment with Tomotherapy and LINAC radiotherapy devices and to examine the accuracy of the surface dose calculated by treatment planning system (TPS) with thermoluminescence dosimetry (TLD). Female Alderson Rando Phantom's chest wall is virtually divided into 9 regions. Computed tomography (CT) images of the phantom were obtained with a section thickness of 3 mm. Two plans, with and without bolus, were created for each of the helical tomotherapy (HT), intensity-modulated radiotherapy (IMRT) and field-in-field (FiF) techniques. A bolus thickness of 0.5 cm was used for all bolus plans. Doses calculated from TPSs were obtained for 88 predetermined points on the chest wall. After irradiation, doses measured with TLDs were obtained. The effect of bolus use on the chest wall surface was examined. The increase in surface dose due to bolus use was 50.35%, 55.35% and 68.56% for HT, IMRT and FiF techniques in TPS, respectively. This increase in TLD measurements was 58.18%, 30.90% and 46.31% for HT, IMRT and FiF techniques, respectively. The best agreement between TPS and TLD doses for bolus and non-bolus plans was found in the HT technique. The difference between TPS and TLD doses decreased within the three treatment techniques due to bolus use. Since the chest wall skin cannot receive the required dose in IMRT and FiF techniques, bolus use is recommended until acute skin reactions occur. There is no need to use a bolus for the HT technique.