Conventional IMRT Research Articles

Comparison of Volumetric Modulated Arc Therapy (VMAT) and Conventional Intensity-Modulated Radiotherapy (IMRT) for Locally Advanced Head and Neck Squamous Cell Carcinoma: A Retrospective Cohort Study.

Purpose This study examines the outcomes of locally advanced head and neck squamous cell carcinoma (HNSCC) following the adoption of conventional intensity-modulated radiotherapy (cIMRT) and volumetric-modulated arc therapy (VMAT) over a decade. The region under study has higher comorbidities associated with increased HNSCC incidence and poorer prognosis. Materials and methods A 10-year retrospective review of electronic medical records included 296 patients with stage III, IVA, and IVB HNSCC (American Joint Committee on Cancer, Seventh edition). Survival outcomes were compared between VMAT and cIMRT using Kaplan-Meier survival curves and adjusted for relevant demographic factors using Cox's proportional hazards model. Analysis was performed using R software(R Foundation, Vienna, Austria). Results The median age of the cohort was 63 years, comprising of 80% males. The oropharynx was the most common primary tumor site. 264 (89%) received 50Gy or higher dose radiation by either cIMRT (22%) or VMAT (67%). At five years, locoregional control (LC) and overall survival (OS) rates were 79.5% and 56.7%, respectively. VMAT showed a significant improvement in five-year OS (63.4% versus 43.8% for cIMRT, p=0.0023)but no significant difference in five-year LC (81% VMAT versus 74.5% cIMRT, p=0.17). Grade 3-4 acute toxicity was observed in 22% of patients. Conclusions VMAT and cIMRT demonstrated excellent LC in locally advanced HNSCCdespite high comorbidity rates. Notably, VMAT was associated with significantly better OS compared to cIMRT. These outcomes surpass historical data, suggesting that VMAT technology may lead to improved patient outcomes. However, larger randomized controlled trials and dosimetric studies are needed to confirm these findings.

Reducing Salivary Toxicity with Adaptive Radiotherapy (ReSTART): A Randomized Controlled Trial Comparing Conventional IMRT to Adaptive IMRT in Head and Neck Squamous Cell Carcinomas

BackgroundThe utility of Adaptive Radiotherapy (ART) in Head and Neck Squamous Cell Carcinoma (HNSCC) remains to be ascertained. While multiple retrospective and single-arm prospective studies have demonstrated its efficacy in decreasing parotid doses and reducing xerostomia, adequate randomized evidence is lacking. Methods and AnalysisReSTART (Reducing Salivary Toxicity with Adaptive Radiotherapy) is an ongoing phase III randomized trial of patients with previously untreated, locally advanced HNSCC of the oropharynx, larynx, and hypopharynx. Patients are randomized in a 1:1 ratio to the standard Intensity Modulated Radiotherapy (IMRT) arm {Planning Target Volume (PTV) margin 5 mm} vs. Adaptive Radiotherapy arm (standard IMRT with a PTV margin 3 mm, two planned adaptive planning at 10th and 20th fractions). The stratification factors include the primary site and nodal stage. The RT dose prescribed is 66Gy in 30 fractions for high-risk PTV and 54Gy in 30 fractions for low-risk PTV over six weeks, along with concurrent chemotherapy.The primary endpoint is to compare salivary toxicity between arms using salivary scintigraphy 12 months' post-radiation. To detect a 25% improvement in the primary endpoint at 12 months in the ART arm with a two-sided 5% alpha value and a power of 80% (and 10% attrition ratio), a sample size of 130 patients is required (65 patients in each arm). The secondary endpoints include acute and late toxicities, locoregional control, disease-free survival, overall survival, quality of life, and xerostomia scores between the two arms. DiscussionThe ReSTART trial aims to answer an important question in Radiation Therapy for HNSCC, particularly in a resource-limited setting. The uniqueness of this trial, compared to other ongoing randomized trials, includes the PTV margins and the xerostomia assessment by scintigraphy at 12 months as the primary endpoint.

62 What is the functional gain?

Swallow optimized IMRT is now supported by level 1 evidence from the phase III DARS trial (CRUK/14/014). By avoiding non-target RT dose to the pharyngeal constrictors, dysphagia optimized IMRT achieved mean MDADI score 7.2 points lower than conventional IMRT as 12 months. What does this mean? Is this a meaningful difference in swallowing function? Will the functional gain be durable into the second decade of survivorship?After a primer on radiation-associated dysphagia in oropharyngeal cancer, the presenter will pragmatically interpret the DARS results from the perspective of a dysphagia specialist - including implications for supportive care. DARS results will be put into context of contemporary function-sparing trials in oropharynx cancer.

Evaluation of conventional IMRT and VMAT strategies for postmastectomy radiation therapy after immediate implant-based reconstruction using the new ESTRO-ACROP contouring guidelines.

This study evaluated the usability of conventional templates based on the new contour guidelines of the European Society of Radiation and Oncology and Advisory Committee in Radiation Oncology Practice (ESTRO-ACROP) for treatment plans of postmastectomy radiotherapy after immediate implant-based reconstruction. Intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) plans generated with two different treatment planning systems (TPSs, Eclipse and Monaco) were examined. Six computed tomography scans of patients aged 35-54years were retrospectively analysed who had undergone mastectomy and breast reconstruction using silicone implants after being diagnosed with left breast cancer. Six radiation oncologists participated in this study, and each of them contoured the target volume of one left breast using conventional contour (CTV-CONV) and new contour (CTV-ESTRO) methods. This study showed that compared with CTV-CONV, using CTV-ESTRO with objectives and cost functions similar to those of TPSs worsened the target volume coverage and increased the total number of monitor units. Considering the organs at risk, CTV-ESTRO tended to increase the mean dose delivered to the contralateral lung. It is concluded that the approach used for the new ESTRO-ACROP contour method cannot be applied in a manner similar to that for the conventional breast contour method, implying that the new ESTRO-ACROP contour method may require more time for improving plans for a given treatment.

Reinforcement Learning Powered Station Parameter Optimized Radiation Therapy (SPORT): A Novel Treatment Planning and Beam Delivery Technique

Conventional intensity modulated radiation therapy (IMRT) with a typical 5-20 fixed beams often does not provide sufficient angular sampling required for conformal dose shaping, whereas current volumetric modulated arc therapy (VMAT) discretizes the angular space into equally spaced control points without considering the differential need for intensity modulation of different angles, leading to undersampling at some angles while oversampling at some other angles. Our goal is to develop a node or station parameter optimized radiation therapy (SPORT) strategy with simultaneously optimized angular sampling and beam modulation by leveraging state-of-the-art reinforcement learning and the unique capability of modern digital LINACs in dose delivery through programmable nodal points. We developed a SPORT optimization framework, in which, the process of programming control points (or station parameters) was formulated as a stochastic dynamic programming problem, which was solved by a reinforcement learning-based algorithm. On-policy reinforcement learning method, namely, state-action-reward-state-action (SARSA) was integrated with deep convolutional neural network to predict station parameters by utilizing the patient's anatomical structures meanwhile considering the delivery capability of a typical digital LINAC machine. Here, the deep convolutional neural network estimated the state-action value by using the quality of the plan with current station parameters when a next potential station parameter was selected. The state-action value was then updated by SARSA learning. The quality of the plan was quantified by dosimetry constraints. The model was assessed by a retrospective study on a cohort of patients underwent head-and-neck radiation therapy. Dosimetric analysis and delivery efficiency comparisons were used to evaluate the performance of the proposed framework. Our model was used to generate 16 plans unseen in the original training set. All the plans predicted by our model achieved better dose distributions without violating clinical planning constraints. Moreover, instead of using 4 full standard arcs in the original clinically used plans obtained via manual optimization, the predicted plans only used one full standard arc (about 178 control points) plus boost from a few sub-arcs (less than 30 degrees of gantry angles), which significantly improved the efficiency of the beam delivery. We are in the process of integrating the sub-arcs into the full arc by considering the programmable capability of modern LINACs. We demonstrated that a machine learning-based SPORT framework capable of optimizing the spatial sampling and beam modulation simultaneously for modern radiation therapy. The framework not only significantly improves the quality and efficiency of beam delivery, but also has the potential to be incorporated into current clinical workflow to improve the efficiency of dose planning and delivery.

Deep Learning-Based Dose Prediction Model for Automated Spot-Scanning Proton Arc Planning

Spot-scanning proton arc (SPArc) is a novel technique that employs a planning optimization algorithm to select the energies and positions of spots along a dynamic rotational arc trajectory. The SPArc technique has the potential to achieve superior dose conformality and treatment delivery efficiency over intensity-modulated proton therapy. However, creating such a SPArc plan using existing approaches is time-consuming and computationally extensively. This study investigated the feasibility of using the deep learning (DL) technique to predict the 3D dose distribution of the SPArc treatment plan, leveraging the prior knowledge acquired from conventional intensity-modulated radiation therapy (IMRT) plans. A DL model, 3D-Unet with residual connections and attention gates, was trained using an open-source database of CT images, critical structures, and IMRT plans from 340 head and neck cancer patients (HNC) as the base model. Transfer learning technique was applied to fine-tune the model parameters using the SPArc treatment plans created on the HNC patients from an in-house dataset, where the SPArc treatment plans (including control point sampling, energy layer distribution, arc trajectory, etc.,) were optimized using a previously developed iterative approach. The performance of the DL model was evaluated by comparing predicted and planned doses over 17 SPArc treatment plans by using 4-fold cross-validation. The SPArc planning time per patient was 8∼12 hours, while the dose prediction time was reduced to 2∼3 minutes using the proposed DL model. The deviation of D95 in the target was (-1.8±1.6) %. The deviation of the mean dose in the parotids, cord, mandible, and brainstem were (2.5±6.5) %, (-0.5±4.3) %, (1.4±3.9) %, and (3.4±8) % of the prescription, respectively. The dice similarity coefficients of the 80%, 70%, and 60% isodose lines were (0.9±0.09), (0.93±0.01), and (0.94±0.01), respectively. Our results demonstrate that a DL-based dose prediction model can be created with a limited number of SPArc treatment plans through transfer learning. The DL model can directly predict the 3D dose distribution in minutes for automated planning. This study paves the roadmap to develop a quick clinical decision platform for the optimal selection among the multi-treatment modalities.

Characteristics of Premature Radiotherapy Terminations in Patients with Oral Cavity and Laryngeal Carcinomas

Premature radiation therapy (RT) terminations in patients with head and neck cancer result in poor outcomes. However, the underlying factors that contribute to early RT termination are understudied, especially in the era of hypofractionated treatment. In this retrospective single institution study, we examined causes and clinical characteristics of premature terminations in oral cavity (OC) and laryngeal carcinomas. We reviewed charts of 188 patients treated with RT ± systemic therapy for OC and laryngeal cancer from 2017-2022. Patients were typically prescribed standard 1.8-2.0 Gy fractionation regimens, though patients deemed unlikely to complete conventional RT upon initial evaluation were given SBRT. Premature termination was defined as completion of less than 95% prescribed RT. We collected pertinent demographic, clinicopathological data on this termination cohort, which was compared to a matched cohort of patients with RT completion. We used logistic regression analysis to examine factors predictive of premature termination. Of the patients included in this analysis, 72.7% were prescribed adjuvant RT [9.1% OC, 45.5% larynx] vs. 27.3% primary RT [90.9% OC, 45.5% larynx]. 84.6% received conventional IMRT, while 15.4% received SBRT. 17 patients (9.0%) had premature RT (all IMRT) terminations- 9 OC and 8 laryngeal primaries. Mean age of those who had premature termination was 79.5 years (range: 70-98). 70.6% were male, 58.8% were white, and 23.5% were single/widowed. Majority received concurrent systemic therapy (58.8%), had AJCC (8th Ed.) Stage ≥ III (76.5%), Charlson-Comorbidity Index ≥6 (64.7%), ECOG score ≥2 (70.6%), smoked >10 pack-years (76.5%), and lived >10 miles from RT facility (58.8%). The most common documented reasons for premature termination were: subjective intolerance (29.4%), death (23.5%), objective RT toxicity (23.5%), and inpatient admission (17.6%). The mean time on treatment for IMRT was 27.8 days for termination cohort vs. 47.7 days for completion cohort. The percentage of patients reporting RT toxicity (CTCAE v5.0 mucositis, severe weight loss, oral infection, e.g.) was 88.2% for termination cohort vs. 29.6% for completion cohort. On regression analysis, ECOG score at the time of initiation of RT was independently associated with premature termination (OR: 2.438, 95% CI: 1.155-5.146, p = .019). This retrospective analysis of patients undergoing RT for OC and laryngeal cancers at our tertiary care center demonstrated nearly 1 in 10 patients are at risk for premature termination. Poor performance status was independently associated with premature termination. There was a 100% completion rate in hypofractionated treatment with SBRT. Taken together, poor performance status may identify patients at risk for premature termination and thus identify good candidates for SBRT protocols.

Planning Considerations for the Primary Lung Tumor Stereotactic Body Radiation Therapy Followed by Concurrent Mediastinal Radiotherapy for Locally-Advanced Non-Small Cell Lung Cancer

Phase III prospective randomized trial of primary lung tumor stereotactic body radiation therapy followed by concurrent mediastinal chemoradiation for locally-advanced non-small cell lung cancer (NRG LU-008), designed to lower the rates of radiation pneumonitis and improve the progression-free survival, is expected to become active nationally in July 2023. Due to the specific nature of the cases selected for this trial, a new approach to treatment planning had to be developed to satisfy the conditions of the trial. Levice Cancer Institute (Atrium Health, North Carolina) ran the initial Phase II trial and investigated several approaches, providing recommendations for the future dosimetry planning approach. A total of 60 patients were selected for the initial trial and treated with a combination of SBRT treatment to the primary tumor (50-54 Gy in 3-5 fractions) and conventional IMRT treatment to 60 Gy to the involved lymph nodes for patients with stage 3 or unresectable stage II NSCLC, combined with chemotherapy. Depending on the location of the primary tumor, all cases could be subdivided into no overlap between the SBRT and IMRT targets, adjacent targets, and overlapping targets. All SBRT plans were done with a 6X-FFF beam, advanced dose calculation algorithm, and 0.1 cm grid size. IMRT targets were primarily treated with VMAT plans, though a minority of cases were planned with the DMLC technique, with a 6X beam, advanced dose calculation algorithm, and 0.25 cm grid size. Various approaches to the planning included target cropping, avoidance via adjusting optimization objectives and utilizing the base dose of the SBRT plan to optimize the dose for the IMRT nodal plan. Various geometries utilized in the plan included a variation in the number of arcs, covered arc angles, and the number of beams. A significant reduction in the side effects was achieved throughout the trial, with only three patients experiencing grade 3 or higher pneumonitis, 3 patients experiencing grade 3 or higher cardiotoxicity, and 1 patient experiencing grade 3 esophagitis. For targets with no significant overlap between the primary tumor and nodal target, standard planning techniques proved to be sufficient. For the overlapping targets, the planning approach of utilizing 2 arcs, >180-degree coverage, for the SBRT plan, and using ¼ of the base SBRT dose to plan the IMRT nodal plan provided the best target coverage while achieving sufficient OAR sparing. Planning the joint SBRT-IMRT plan in the cases of a significant target overlap requires a careful approach, but is feasible with the proposed guideline and should be achievable for any center electing to participate in the NRG LU-008 trial.

Observation of hemostatic effectiveness and safety of ultrasound-CT guided 3D intracavitary and interstitial brachytherapy in the treatment of larger cervical cancer with bleeding: A retrospective study.

Cervical cancer is the fourth most frequently diagnosed cancer and the fourth leading cause of cancer death in women. This study explored the effectiveness and safety of ultrasound-CT guided 3D intracavitary and interstitial brachytherapy (US-CT-3D-IGBT) in the treatment of larger cervical cancer with bleeding. A retrospective study was conducted on 31 patients with larger cervical squamous cell carcinoma (tumor short diameter >4 cm) with vaginal bleeding. US-CT-3D-IGBT was used to deliver a single high-dose prescription of high-risk clinical target volume (HR-CTV) 1000 to 1200 centigray (cGy) to the cervical tumor, followed by conventional intensity-modulated radiation therapy (IMRT) synchronous chemoradiotherapy (45-50 gray (Gy)/25-28 fraction(f)) with weekly cisplatin 25 mg/m2. After external radiotherapy, simple intracavitary brachytherapy (BT) combined with manual interstitial BT was administered at 30 Gy/5F or 28 Gy/4F. Within 24 hours after high-dose 3D-IGBT, bleeding stopped in 2 patients (6.4%), and bleeding was reduced in a total of 11 patients (35.4%) within 48 hours. A total of 29 patients achieved hemostasis within 72 hours, with an effective rate of 93.5%. The remaining 2 patients reached the clinical hemostasis requirement on the 4th and 5th day. All patients experienced a significant reduction in vaginal bleeding after the initial BT, with an average reduction of 66 mL (160-20 mL). US-CT-3D-IGBT is effective in rapidly controlling bleeding in patients with larger cervical cancer (tumor short diameter >4 cm), and the treatment is relatively safe and feasible.

Accounting for fractionation and heterogeneous dose distributions in the modelling of osteoradionecrosis in oropharyngeal carcinoma treatment

Background and purposeOsteoradionecrosis (ORN) of the mandible is a severe complication following radiotherapy (RT). With a renewed interest in hypofractionation for head and neck radiotherapy, more information concerning ORN development after high fraction doses is important. The aim of this explorative study was to develop a model for ORN risk prediction applicable across different fractionation schemes using Equivalent Uniform Doses (EUD). Material and methodsWe performed a retrospective cohort study in 334 oropharyngeal squamous cell carcinoma (OPSCC) patients treated with either a hypofractionated Stereotactic Body Radiation Therapy (HF-SBRT) boost or conventional Intensity Modulated Radiation Therapy (IMRT). ORN was scored with the CTCAE v5.0. HF-SBRT and IMRT dose distributions were converted into equivalent dose in 2 Gy fractions (α/β = 0.85 Gy) and analyzed using EUD. The parameter a that led to an EUD that best discriminated patients with and without grade ≥ 2 ORN was selected. Patient and treatment-related risk factors of ORN were analyzed with uni- and multivariable regression analysis. ResultsA total of 32 patients (9.6%) developed ORN grade ≥ 2. An EUD(a = 8) best discriminated between ORN and non-ORN (AUC = 0.71). In multivariable regression, pre-RT extractions (SHR = 2.34; p = 0.012), mandibular volume (SHR = 1.04; p = 0.003), and the EUD(a = 8) (SHR = 1.14; p < 0.001) were significantly associated with ORN. ConclusionRisk models for ORN based on conventional DVH parameters cannot be directly applied to HF-SBRT fractionation schemes and dose distributions. However, after correcting for fractionation and non-uniform dose distributions using EUD, a single model can distinguish between ORN and non-ORN after conventionally fractionated radiotherapy and hypofractionated boost treatments.

Analysis of risk factors of radiation-induced toxicity in limited-stage small cell lung cancer treated with hypofractionated intensity-modulated radiotherapy

Objective: To compare the incidence of radiation-related toxicities between conventional and hypofractionated intensity-modulated radiation therapy (IMRT) for limited-stage small cell lung cancer (SCLC), and to explore the risk factors of hypofractionated radiotherapy-induced toxicities. Methods: Data were retrospectively collected from consecutive limited-stage SCLC patients treated with definitive concurrent chemoradiotherapy in Cancer Hospital of Chinese Academy of Medical Sciences from March 2016 to April 2022. The enrolled patients were divided into two groups according to radiation fractionated regimens. Common Terminology Criteria for Adverse Events (CTCAE, version 5.0) was used to evaluate the grade of radiation esophagus injuries and lung injuries. Logistic regression analyses were used to identify factors associated with radiation-related toxicities in the hypofractionated radiotherapy group. Results: Among 211 enrolled patients, 108 cases underwent conventional IMRT and 103 patients received hypofractionated IMRT. The cumulative incidences of acute esophagitis grade ≥2 [38.9% (42/108) vs 35.0% (36/103), P=0.895] and grade ≥ 3 [1.9% (2/108) vs 5.8% (6/103), P=0.132] were similar between conventional and hypofractionated IMRT group. Late esophagus injuries grade ≥2 occurred in one patient in either group. No differences in the cumulative incidence of acute pneumonitis grade ≥2[12.0% (13/108) vs 5.8% (6/103), P=0.172] and late lung injuries grade ≥2[5.6% (6/108) vs 10.7% (11/103), P=0.277] were observed. There was no grade ≥3 lung injuries occurred in either group. Using multiple regression analysis, mean esophageal dose ≥13 Gy (OR=3.33, 95% CI: 1.23-9.01, P=0.018) and the overlapping volume between planning target volume (PTV) and esophageal ≥8 cm(3)(OR=3.99, 95% CI: 1.24-12.79, P=0.020) were identified as the independent risk factors associated with acute esophagitis grade ≥2 in the hypofractionated radiotherapy group. Acute pneumonitis grade ≥2 was correlated with presence of chronic obstructive pulmonary disease (COPD, P=0.025). Late lung injuries grade ≥2 was correlated with tumor location(P=0.036). Conclusions: Hypofractionated IMRT are tolerated with manageable toxicities for limited-stage SCLC patients treated with IMRT. Mean esophageal dose and the overlapping volume between PTV and esophageal are independently predictive factors of acute esophagitis grade ≥2, and COPD and tumor location are valuable factors of lung injuries for limited-stage SCLC patients receiving hyofractionated radiotherapy. Prospective studies are needed to confirm these results.

Simultaneous integrated dose reduction intensity-modulated radiotherapy effectively reduces cardiac toxicity in limited-stage small cell lung cancer.

To assess the clinical outcomes and toxicities of once daily (QD) simultaneous dose reduction intensity-modulated radiotherapy (SDR-IMRT-QD; SDR-QD) versus conventional QD IMRT (C-QD) and twice daily (BID) IMRT in patients with limited-stage small cell lung cancer (LS-SCLC). After propensity score matching (PSM), a retrospective analysis involving 300 patients with LS-SCLC treated using SDR-QD, C-QD, or BID was performed from January 1, 2014 to December 31, 2019. The prescribed irradiation dose in the SDR-QD cohort was 60 Gy/PGTV and 54 Gy/PTV QD. The radiation dose was 60 Gy for both PGTV and PTV QD in the C-QD cohort. The radiation dose was 45 Gy for both PGTV and PTV in the BID cohort. Toxicities, short-term effects, and survival outcomes were recorded. A meta-analysis on the protective effects of pharmaceuticals for cardiac toxicities induced by anti-tumor therapy was performed. The median overall survival time (MST) in the 3 cohorts were 32.7 months (SDR-QD), 26.3 months (C-QD), and 33.6 months (BID); the differences between groups were statistically significant. Lower toxicities and doses to organs-at-risk (OARs) occurred in the SDR-QD and BID cohorts. Further, the cardiac dose dosimetric parameter Vheart40 was negatively associated with survival (r = -0.35, P = 0.007). A Vheart40 value of 16.5% was recommended as a cut-off point, which yielded 54.7% sensitivity and 85.7% specificity for predicting negative survival outcomes. The meta-analysis indicated that pharmaceuticals significantly reduced the cardiac toxicities induced by chemotherapy, but not radiotherapy. SDR-QD was shown to have similar toxicities and survival compared with BID, but fewer toxicities and better survival than C-QD. In addition, cardiac dose exposure was negatively associated with survival. Thus, 16.5% of the cardiac dosimetric parameter Vheart40 is recommended as the cut-off point, and a Vheart40 > 16.5% predicts poor survival.

Ninety-degree angled collimator: a dosimetric study related to dynamic intensity-modulated radiotherapy in patients with endometrial carcinoma

BackgroundOur purpose was to ensure that the dose constraints of the organs at risk (OARs) were not exceeded while increasing the prescription dose to the planning target volume (PTV) from 45 to 50.4 Gray (Gy) with the dynamic intensity-modulated radiotherapy (IMRT) technique. While trying for this purpose, a new dynamic IMRT technique named 90° angled collimated dynamic IMRT (A-IMRT) planning was developed by us.MethodsThis study was based on the computed tomography data sets of 20 patients with postoperatively diagnosed International Federation of Gynecology and Obstetrics stage 2 endometrial carcinoma. For each patient, conventional dynamic IMRT (C-IMRT, collimator angle of 0° at all gantry angles), A-IMRT (collimator angle of 90° at gantry angles of 110°, 180°, 215°, and 285°), and volumetric modulated arc therapy (VMAT) were planned. Planning techniques were compared with parameters used to evaluate PTV and OARs via dose-volume-histogram analysis using the paired two-tailed Wilcoxon’s signed-rank test; p < 0.05 was considered indicative of statistical significance.ResultsAll plans achieved adequate dose coverage for PTV. Although the technique with the lowest mean conformality index was A-IMRT (0.76 ± 0.05) compared to both C-IMRT (0.79 ± 0.04, p = 0.000) and VMAT (0.83 ± 0.03, p = 0.000), it protected the OARs especially the bladder (V45 = 32.84 ± 2.03 vs. 44.21 ± 6.67, p = 0.000), rectum (V30 = 56.18 ± 2.05 vs. 73.80 ± 4.75, p = 0.000) and both femoral heads (V30 for right = 12.19 ± 1.34 vs. 21.42 ± 4.03, p = 0.000 and V30 for left = 12.58 ± 1.48 vs. 21.35 ± 4.16, p = 0.000) better than C-IMRT. While the dose constraints of the bladder, rectum and bilateral femoral heads were not exceeded in any patient with A-IMRT or VMAT, they were exceeded in 19 (95%), 20 (100%) and 20 (100%) patients with C-IMRT, respectively.ConclusionsOARs are better protected when external beam radiotherapy is applied to the pelvis at a dose of 50.4 Gy by turning the collimator angle to 90° at some gantry angles with the dynamic IMRT technique in the absence of VMAT.

Comparative Study between Patients Treated with Conventional Radiotherapy and IMRT with Chemotherapy for Stage III - IVA Nasopharyngeal Carcinoma: A Single Institution Retrospective Report

Comparative Study between Patients Treated with Conventional Radiotherapy and IMRT with Chemotherapy for Stage III - IVA Nasopharyngeal Carcinoma: A Single Institution Retrospective Report

Escalation of radiotherapy dose in large locally advanced drug-resistant gastrointestinal stromal tumors by multi-shell simultaneous integrated boost intensity-modulated technique: a feasibility study

BackgroundResistance to conventional dose schemes and radiotoxicity of healthy tissue is a clinical challenge in the radiation therapy of large locally advanced drug-resistant gastrointestinal stromal tumor (LADR-GIST). This study aimed to assess the feasibility of using multi-shell Simultaneous Integrated Boost Intensity-Modulated modality (SIB-IMRT) strategy to provide a safe and effective escalation dose regimen for LADR-GIST.Methods7 patients with LADR-GIST were selected in this study. The modified SIB-IMRT plans for all patients were generated by delivering different escalation-dose gradients to four ring shaped regions (shells) within the gross tumor volume (GTV). The doses of the central volume of the tumor (GTVcenter) were escalated up to 70–92.5 Gy (25 fractions), while the doses of planning target volume (PTV) and shell-1 were kept at 50.0 Gy. Based on different escalation-dose gradients, the modified SIB-IMRT plans were divided into four groups (SIB-IMRT groups). For comparison purposes, plans obtained by conventional IMRT technique (Con-IMRT) with 50 Gy (25 fractions) were also generated for all patients (Con-IMRT group). All plans were normalized to cover 95% of the PTV with the prescribed dose of 50.0 Gy. The equivalent uniform dose (EUD), relative equivalent uniform dose (rEUD), dose volume histogram (DVH), dose profile, conformity index (CI) and monitor unit (MU) were evaluated in five groups. The Friedman Test was performed to determine whether there were significant differences (P < 0.05).ResultsCompared with the Con-IMRT group, the EUD of GTV (EUDGTV) and rEUD of SIB-IMRT groups were improved when escalation-dose gradient was increased, and the improvement became significant when the escalation-dose gradient reached 20% of the prescription dose. The rEUD tended to be stable as the escalation-dose gradient went up to 25% of the prescription dose. There were no significant differences in CIs and DVH metrics for OARs between the Con-IMRT group and any SIB-IMRT group, but the significant differences were observed between the SIB10-IMRT group and the SIB25-IMRT group. For the SIB-IMRT groups, as the dose gradient became steeper in the dose profiles, the higher dose was mainly accumulated in the inner part of GTV accompanied with a higher MU.ConclusionsThe proposed multi-shell SIB-IMRT strategy is feasible in dosimetry for LADR-GIST and can acquire higher therapeutic gain without sacrifice of healthy tissues. It appears that the scheme of delivering 20% of the prescribed escalation-dose gradient to the target volume can provide satisfactory dose irradiation for LADR-GIST, and it should be evaluated in future clinical study.

SURVIVAL AND LONGTERM TOXICITIES OUTCOMES IN ADAPTIVE INTENSITY-MODULATED RADIOTHERAPY (ART) VS IMRT IN LOCALLY ADVANCED HEAD AND NECK CANCER.

Background: Anatomic complexity is a challenge for radiation oncologist.Repeated CT scans and replanning can overcome the variations in terms of size or shape a tumour has undergone during treatment , this process has been termed as Adaptive Radiotherapy(ART). The use of adaptive approach or IMRT-SIB is still under debate since there is not enough evidence of long-term clinical outcomes , metastasis free survival. Total Sixty patients Materials And Methods: with locally advanced HNC with a intent to cure were assigned into two arms to receive IMRT up to a dose of 70 Gy with concurrent weekly chemotherapy and were prospectively analyzed between March 2018 and March 2019. Repeat CT scan was acquired after the 3rd week of radiation and those in the study arm were replannned and those in the controlarm continued with the rst IMRT plan. For the entire cohort, patients were assessed weekly till the end of treatment and at 1, 3, and6 months, 1 year and 2 years thereafter. Main focus was on Xerostomia status at end of 6 months and end of 2 years and Survival (OS) rates at end of 2-years was calculated and hence compared. 2 years overall survival rate wa Results: s almost similar with 73.33% vs 76.66% in adaptive IMRTand conventional IMRT respectively; p value= 0. 23 Xerostomia was statistically signicantly higher in the conventional arm at 6 months(p=0.01).Grade ≥II xerostomia at end of 2 years reduced to 0% vs 4.43 %in adaptive and conventional IMRT respectively (p= 0.78). Conclusion: Adaptive IMRT can help to minimise xerostomia at end of 6 months .However no major benet in survival when compared 2 year after completion of treatment.

Comparison of Simultaneous Integrated Boost IMRT for Dose Escalation (54 Gy) and Conventional IMRT (45 Gy) Twice Daily Combined with Concurrent Chemotherapy for Limited-Stage Small-Cell Lung Cancer: Analysis of Two Prospective Trials

<h3>Purpose/Objective(s)</h3> Twice-daily thoracic radiotherapy (TRT) with concurrent chemotherapy is standard for limited-stage small-cell lung cancer (LS-SCLC). However, the importance of twice-daily simultaneous integrated boost intensity-modulated radiotherapy (SIB-IMRT) has not been clearly defined in LS-SCLC. Therefore, we conducted a prospective single arm, multicenter phase II study of SIB-IMRT for dose escalation (54 Gy) to the gross tumor volume for LS-SCLC. Here, we compared SIB-IMRT for dose escalation (54 Gy) to the gross tumor volume versus conventional intensity-modulated radiotherapy (IMRT) of standard-dose (45 Gy) twice-daily combined with concurrent chemotherapy in patients with LS-SCLC. <h3>Materials/Methods</h3> Sixty patients with LS-SCLC were entered from 2015 to 2021 in the phase II study of SIB-IMRT, and all 60 patients were treated with SIB-IMRT to the postchemotherapy tumor volume, as the SIB-IMRT group. In the SIB-IMRT group, the prescribed dose was 54Gy at 1.8 Gy twice daily to PGTV, and 45 Gy at 1.5 Gy twice daily to PCTV. We previously conducted a prospective phase III study on thoracic radiotherapy (TRT) target volumes for LS-SCLC (Cancer, 2020, 126(4), 840-849). In that study, from 2012-2017, 85 patients received thoracic IMRT to the postchemotherapy tumor volume, as the IMRT group. In the IMRT group, the prescribed dose was 45 Gy at 1.5 Gy per twice-daily fraction to both the planning gross tumor volume (PGTV) and the planning clinical tumor volume (PCTV). All of the 145 patients in both groups received concurrent chemoradiotherapy (CCRT) after completion of 2 cycles of induction cisplatin-etoposide chemotherapy, and received chemotherapy for 4 to 6 cycles in total. We compared progression free survival (PFS) and overall survival (OS) between the treatment groups by using the Kaplan-Meier method. <h3>Results</h3> Overall, with a median follow-up of 34.6 months, the median PFS and OS were 11.9 and 23.7 months, respectively. The patients in the SIB-IMRT group showed marginal longer PFS than those in the IMRT group (13.3 months versus 11.5 months; <i>p</i> = 0.08). The median OS of the SIB-IMRT and IMRT groups were 35.0 and 20.3 months, with the 2-year OS rate of 66.1% and 38.8%, respectively (<i>p</i> =0.007). For radiotherapy toxicity, grade 2 acute esophagitis was more common in the SIB-IMRT group, but grade≥3 esophagitis and grade≥2 pneumonitis was no difference in both two groups. <h3>Conclusion</h3> For LS-SCLC patients, SIB-IMRT for dose escalation (54 Gy at 1.8Gy twice daily) to PGTV benefited survival greatly. Our results suggest that SIR-IMRT is safe and effective for patients with LS-SCLC and should be further evaluated in a large prospective clinical trial.

Systematic Study of Patient-Specific Organs at Risk Auto-Segmentation on Daily kVCT Images for Adaptive Head and Neck Radiotherapy

<h3>Purpose/Objective(s)</h3> A newly developed biology-guided radiotherapy (BgRT) system has been set up in our institution, which enables high-quality kVCT imaging for each treatment fraction. This study explored deep learning-based patient-specific auto-segmentation to facilitate adaptive radiotherapy, based on data of the first head and neck patient case treated with this new system. <h3>Materials/Methods</h3> The esophagus, larynx, and pharynx were selected as the organs at risk (OAR) for auto-segmentation analysis. A population network was first learned on a population dataset, which contains 67 different patient cases from conventional intensity-modulated radiotherapy (IMRT). Then the pre-trained population network was adapted to this specific patient using a transfer learning method based on the longitudinal data from the initial treatment planning and 17 sets of daily image guidance kVCT images. The selected OARs were contoured by a radiation oncologist on 18 sets of images as the ground truth. The performance of the patient-specific network was compared with the population network as well as the clinical rigid registration method. The corresponding dosimetric impacts resulting from different segmentation and registration methods were also investigated. <h3>Results</h3> The initial Dice similarity coefficient (DSC) results of the population network on the patient-specific evaluation set were 0.821, 0.537, 0.739 for esophagus, larynx, and pharynx respectively, and they were markedly improved to 0.887, 0.889, 0.850 with the proposed patient-specific network. These results also outperformed the results of 0.670, 0.792, 0.709 with the registration-based method in current clinical practice. The contouring accuracy of the patient-specific network gradually increased with the increase of longitudinal training cases and approached saturation with more than six training cases. The qualification result also shows the population network was adapted to the specific manual contouring style after the patient-specific learning. Discrepancies of the mean doses by using the manual contour and the patient-specific auto-segmentation result were -1.29%, -1.05%, -0.13% for the three OARs respectively, better than the differences of 4.80%, -6.56%, -1.84% using the registration contour. The OAR dose underestimation in some treatment fractions based on the registration contour was markedly improved when using the patient-specific auto-segmentation result. <h3>Conclusion</h3> Auto-segmentation of daily kVCT images was studied based on patient-specific learning to facilitate future adaptive radiotherapy. Compared with the common population network and the clinical registration method, the patient-specific network could achieve a much better contouring and dosimetric accuracy and thus is promising to become a powerful tool in adaptive radiotherapy applications.

Simultaneous Modulated Accelerated Radiotherapy (SMART) with Dysphagia Aspiration-Related Structures (DARS) Sparing: Do We Have a Role for Dose Condensation in Locally Advanced Head and Neck Cancer

Introduction Concurrent chemotherapy integrated with intensity-modulated radiotherapy (IMRT) is the standard of care for locally advanced head and neck cancer. Simultaneous integrated boost technique has allowed differential doses to primary and normal structures permitting significant toxicity reduction. The current study explores the feasibility of the simultaneous modulated accelerated radiotherapy (SMART) technique to enhance cytoreduction and explore the possibility of dose intensification with radiobiologically targeted treatment condensation. Methods Thirty patients were randomized in an open-labeled study to receive concurrent chemoradiation of 60 Gy in 25 fractions with “SMART” technique or 70 Gy in 35 fractions using conventional intensity-modulated radiotherapy simultaneous integrated boost “IMRT SIB.” The primary endpoints included comparative volumetric cytoreduction between the study and control arm assessed during the course of treatment and final response evaluation. Secondary endpoints involved the assessment of acute toxicity parameters for xerostomia, mucositis, dysphagia, and fatigue. Results The “SMART” study arm showed comparable volumetric cytoreduction to the conventional “IMRT SIB” arm at midtreatment (p-value = 0.225) as well as toward completion (p-value = 0.476). The study arm did observe 94.4% cytoreduction of tumor volume compared with 88.05% in the conventional arm at the time of response evaluation. In spite of treatment condensation, there was no significant increase in toxicity with “SMART.” There was no difference in the frequency or duration of grade 3 mucositis in the “SMART” arm in spite of intensification (p-value = 0.728). In the “SMART” arm, there was a favorable reduction in the duration of grade ⅔ dysphagia; 2.8 weeks versus 4.6 weeks (p-value = 0.002). Even though the xerostomia was comparable in frequency and intensity, the total duration of xerostomia was 50% less (p-value = 0.001). Conclusions The “SMART” technique provides a radiobiologically sound, effective, and safe protocol that has the potential to improve the treatment of locally advanced head and neck cancer. The good tolerability and toxicity profile in the study arm is encouraging and facilitates further research.

Dosimetric effects of oral contrast in the planning of conventional radiotherapy and IMRT, for rectal cancer treatment

Abstract Introduction: Contrast media are frequently used during radiation therapy simulation. However, there are concerns about dosimetric variations when dose calculation is done on contrast-enhanced computed tomography (CT). This study evaluates the dosimetric effect of oral contrast during three-dimensional conformal radiotherapy (3D-CRT) and volumetric modulated arc radiotherapy (VMAT) planning. Methods: Rectal cancer patients were consecutively enrolled. For each patient, one unenhanced CT and one contrast-enhanced CT were taken using oral and intravenous contrast. Then, a 3D-CRT plan and an Intensity-modulated radiation therapy (IMRT)/VMAT plan were generated in the enhanced CT, and the dose distribution was recalculated in the respective unenhanced CT. The beam intensities were kept the same as for the enhanced CT plans. Finally, the unenhanced and enhanced plans were compared by calculating the gamma index. Results: For 3D-CRT plans, there were statistically significant differences in second phase planning target volume (PTV) D2% (Mean difference (MD) between unenhanced and enhanced CT 0·01 Gy, 95% CI [0·003 to 0·02 Gy]) and in maximum doses to the bladder (MD 0·26 Gy, 95% CI [0·05 to 0·47 Gy]). For IMRT/VMAT plans, there were statistically significant differences in small intestine V45 Gy (MD 3·1 cc, 95% CI [0·81 to 5·4 cc]), bladder V45 Gy (MD 2·9%, 95% CI [1·4 to 4·3%]) and maximum dose to the bladder (MD 0·65 Gy, 95% CI [0·46 Gy to 0·85 Gy]). In addition, for PTV D98% the MD between unenhanced and enhanced CT was 0·22 Gy 95% CI [0·05 to 0·39]. Conclusions: For most of the dose metrics, the differences were not clinically meaningful. The greatest differences were found in VMAT plans, especially in V45 Gy of the small intestine. This difference could lead to an underestimation of dose–volume metrics when the plan is based on an enhanced CT. The use of small bowel oral contrast does not significantly influence dose calculations and may not affect the acceptability of plans when adhering to constraints.