Comparative dosimetric analysis of normal brain tissue in patients with Nasopharyngeal carcinoma at different stages after radiation therapy.

INTRODUCTION: Radiotherapy (RT) is the main treatment for patients with nasopharyngeal carcinoma (NPC). NPC patients at different stages have varying levels of damage to normal brain tissue after RT. No study has yet thoroughly analyzed the variations in radiation dosages in the brain for different stages of NPC patients treated with RT. This study aims to examine these variations. METHODS: 1446 NPC patients' CT and RTdose data were retrospectively reviewed. Analysis of the radiation dosage was executed on these 803 patients. The RTdose images for several patient groups were averaged after registering each patient's RTdose data to the CT brain template created in our earlier study. The voxel-based (VB) analysis was used to examine the dose variations in the brains of three groups of NPC patients: the early-stage group, the stage III group, and the stage IV group. RESULTS: As the disease progresses from early to advanced stages, the intensity and volume of radiation in the brain increase. The normal brain tissue accepted a substantially larger dosage in more advanced NPC patients. Differences in brain regions between stage III and early-stage patients were minimal compared to any other two groups. Brain regions exhibited substantial variations between the stage IV group and all other patient groups were broadly distributed. CONCLUSION: Our findings highlight the critical role of NPC staging in the therapeutic strategy, emphasizing the heterogeneity of radiation-induced tissue damage across disease stages and implying the need to develop stage-specific RT plans.

Specific-CT brain template construction and retrospective dosimetric comparison study in brain for nasopharyngeal carcinoma patients treated with IMRT or VMAT.

The current Radiotherapy (RT) technology still inevitably irradiated normal brain tissue, causing implicit radiation-induced injury. This study investigates the precise localization and the corresponding radiation dosage of brain regions susceptible to damage in nasopharyngeal carcinoma (NPC) patients following RT. Utilizing the Advanced Normalization Tools (ANTs) package, a computed tomography (CT) brain template was created in the standard Montreal Neurological Institute (MNI) space, based on 803 Chinese NPC patients (T0~T4) who underwent RT. With this template, all patients' CT and RTdose data were registered to the MNI space, and the RTdose distribution characteristics in normal brain tissues were compared for NPC patients treated with Intensity-modulated radiotherapy (IMRT) or Volumetric Modulated Arc Therapy (VMAT), with patients' age and gender as covariates. Analysis of the average dosages indicated that certain areas within the Limbic, Temporal, and Posterior Lobes, the Brainstem, and the Cerebellum Posterior Lobe were exposed to doses exceeding 50 Gy. Inter-group analysis revealed that IMRT delivered higher doses than VMAT to brain regions anterior to the nasopharyngeal tumor, whereas VMAT affected the posterior regions more. Interestingly, VMAT showed a drawback in preserving the normal brain tissues for T4-stage patients. This revealed that the two treatment modalities have unique characteristics in preserving normal brain tissue, each with advantages. With better localization precision, the created CT brain template in MNI space may be beneficial for NPC patients' toxicity and dosimetric analyses.

Single isocenter versus dual isocenter treatment using flattening filter-free and jaw-tracking volumetrically modulated arc therapy for boot-shaped lung cancer: Evaluation of dosimetric and feasibility.

BACKGROUND: To determine whether a dual-isocenter volumetrically modulated arc therapy (VMAT) technique results in lower normal pulmonary dosage compared to a traditional single isocenter technique for boot-shaped lung cancer. METHODS: A cohort of 15 patients with advanced peripheral or central lung cancer who had metastases in the mediastinum and supraclavicular lymph nodes was randomly selected for this retrospective study. VMAT plans were generated for each patient using two different beam alignment techniques with the 6-MV flattening filter-free (FFF) photon beam: single-isocenter jaw-tracking VMAT based on the Varian TrueBeam linear accelerator (S-TV), and dual-isocenter VMAT based on both TrueBeam (D-TV) and Halcyon linear accelerator (D-HV). For all 45 treatment plans, planning target volume (PTV) dose coverage, conformity/homogeneity index (CI/HI), mean heart dose (MHD), mean lung dose (MLD) and the total lung tissue receiving 5, 20, 30 Gy (V5, V20, V30) were evaluated. The monitor units (MUs), delivery time, and plan quality assurance (QA) results were recorded. RESULTS: The quality of the objectives of the three plans was comparable to each other. In comparison with S-TV, D-TV and D-HV improved the CI and HI of the PTV (p < 0.05). The MLD was 13.84 ± 1.44 Gy (mean ± SD) for D-TV, 14.22 ± 1.30 Gy and 14.16 ± 1.42 Gy for S-TV and D-HV, respectively. Lungs-V5Gy was 50.78 ± 6.24%, 52.00 ± 7.32% and 53.36 ± 8.48%, Lungs-V20Gy was 23.72 ± 2.27%, 26.18 ± 2.86% and 24.96 ± 3.09%, Lungs-V30Gy was 15.69 ± 1.76%, 17.20 ± 1.72% and 16.52 ± 2.07%. Compared to S-TV, D-TV provided statistically significant better protection for the total lung, with the exception of the lungs-V5. All plans passed QA according the gamma criteria of 3%/3 mm. CONCLUSIONS: Taking into account the dosimetric results and published clinical data on radiation-induced pulmonary injury, dual-isocenter jaw-tracking VMAT may be the optimal choice for treating boot-shaped lung cancer.

A detailed dosimetric comparative study of IMRT and VMAT in normal brain tissues for nasopharyngeal carcinoma patients treated with radiotherapy.

Background: Radiotherapy (RT) is the primary treatment for nasopharyngeal carcinoma (NPC). However, it can cause implicit RT-induced injury by irradiating normal brain tissue. To date, there have been no detailed reports on the radiated exact location in the brain, the corresponding radiation dose, and their relationship. Methods: We analyzed 803 Chinese NPC patients treated with RT and used a CT brain template in a Montreal Neurological Institute (MNI) space to compare the group differences in RT dose distribution for different RT technologies (IMRT or VMAT). Results: Brain regions that received high doses (>50 Gy) of radiation were mainly located in parts of the temporal and limbic lobes, where radioactive damage often occurs. Brain regions that accepted higher doses with IMRT were mainly located near the anterior region of the nasopharyngeal tumor, while brain regions that accepted higher doses with VMAT were mainly located near the posterior region of the tumor. No significant difference was detected between IMRT and VMAT for T1 stage patients. For T2 stage patients, differences were widely distributed, with VMAT showing a significant dose advantage in protecting the normal brain tissue. For T3 stage patients, VMAT showed an advantage in the superior temporal gyrus and limbic lobe, while IMRT showed an advantage in the posterior cerebellum. For T4 stage patients, VMAT showed a disadvantage in protecting the normal brain tissue. These results indicate that IMRT and VMAT have their own advantages in sparing different organs at risk (OARs) in the brain for different T stages of NPC patients treated with RT. Conclusion: Our approach for analyzing dosimetric characteristics in a standard MNI space for Chinese NPC patients provides greater convenience in toxicity and dosimetry analysis with superior localization accuracy. Using this method, we found interesting differences from previous reports: VMAT showed a disadvantage in protecting the normal brain tissue for T4 stage NPC patients.

Dosimetric advantages of robust optimization combined with flattening filter free in treating cancer of the left breast.

OBJECTIVE: By comparing the target dose distribution with or without the robust optimization, the dosimetric advantages of robust optimization and flattening filter free (FFF) in radiation therapy for postmastectomy cancer of the left breast was explored when part of the chest wall target was moved out in case of respiratory motion. MATERIALS AND METHODS: This is a retrospective study. The data of 21 postmastectomy patients with cancer of the left breast from 2019 to 2020 were retrospectively collected. The planned target volume (PTV) dose was prescribed 50 Gy/25 fractions and the treatment plans were designed using 6 MV FFF X ray and volumetric modulated arc therapy (VMAT) technology in RayStation treatment planning system (TPS), with and without robust optimization. The movement of the target area of the internal chest wall (0.50 cm) caused by respiratory movement was simulated by moving the isocenter of the beams. RESULTS: When the chest wall target moved outward, the PTV target area D98, D95, D2, conformity index (CI) and homogeneity index (HI) with robust optimization were better than those without robust optimization. The coverage rate of Planned Target Volume-Chest (PTV-T) V50 with robust optimization was significantly higher than that with no-robust optimization (P<0.001). Clinical target volume (CTV) V50 coverage with robust optimization was 14.49% higher than that with no-robust optimization. In terms of organ-at-risk parameters, the average spinal cord dose of the plan with robust optimization was 13.19% lower than that of the plan with no-robust optimization, and the Lung-L V5 of the plan with no-robust optimization was slightly (1.94%) lower than that of the plan with robust optimization. There was no significant difference in machine execution efficiency between the two groups (P>0.05). CONCLUSIONS: Robust optimization could be adopted in the postoperative radiotherapy planning for cancer in the left breast, for it ensures that the target dose coverage and the dose limit of organ-at-risk still meet the clinical requirements under condition of chest wall displacement caused by respiratory movement.

Fully convolutional network-based multi-output model for automatic segmentation of organs at risk in thorax.

PURPOSE: To propose a multi-output fully convolutional network (MOFCN) to segment bilateral lung, heart and spinal cord in the planning thoracic computed tomography (CT) slices automatically and simultaneously. METHODS: The MOFCN includes two components: one main backbone and three branches. The main backbone extracts the features about lung, heart and spinal cord. The extracted features are transferred to three branches which correspond to three organs respectively. The longest branch to segment spinal cord is nine layers, including input and output layers. The MOFCN was evaluated on 19,277 CT slices from 966 patients with cancer in the thorax. In these slices, the organs at risk (OARs) were delineated and validated by experienced radiation oncologists, and served as ground truth for training and evaluation. The data from 61 randomly chosen patients were used for training and validation. The remaining 905 patients' slices were used for testing. The metric used to evaluate the similarity between the auto-segmented organs and their ground truth was Dice. Besides, we compared the MOFCN with other published models. To assess the distinct output design and the impact of layer number and dilated convolution, we compared MOFCN with a multi-label learning model and its variants. By analyzing the not good performances, we suggested possible solutions. RESULTS: MOFCN achieved Dice of 0.95 ± 0.02 for lung, 0.91 ± 0.03 for heart and 0.87 ± 0.06 for spinal cord. Compared to other models, MOFCN could achieve a comparable accuracy with the least time cost. CONCLUSION: The results demonstrated the MOFCN's effectiveness. It uses less parameters to delineate three OARs simultaneously and automatically, and thus shows a relatively low requirement for hardware and has potential for broad application.

FocusNetv2: Imbalanced large and small organ segmentation with adversarial shape constraint for head and neck CT images.

Radiotherapy is a treatment where radiation is used to eliminate cancer cells. The delineation of organs-at-risk (OARs) is a vital step in radiotherapy treatment planning to avoid damage to healthy organs. For nasopharyngeal cancer, more than 20 OARs are needed to be precisely segmented in advance. The challenge of this task lies in complex anatomical structure, low-contrast organ contours, and the extremely imbalanced size between large and small organs. Common segmentation methods that treat them equally would generally lead to inaccurate small-organ labeling. We propose a novel two-stage deep neural network, FocusNetv2, to solve this challenging problem by automatically locating, ROI-pooling, and segmenting small organs with specifically designed small-organ localization and segmentation sub-networks while maintaining the accuracy of large organ segmentation. In addition to our original FocusNet, we employ a novel adversarial shape constraint on small organs to ensure the consistency between estimated small-organ shapes and organ shape prior knowledge. Our proposed framework is extensively tested on both self-collected dataset of 1,164 CT scans and the MICCAI Head and Neck Auto Segmentation Challenge 2015 dataset, which shows superior performance compared with state-of-the-art head and neck OAR segmentation methods.

Automatic Planning for Nasopharyngeal Carcinoma Based on Progressive Optimization in RayStation Treatment Planning System.

OBJECTIVE: To evaluate and quantify the planning performance of automatic planning (AP) with manual planning (MP) for nasopharyngeal carcinoma in the RayStation treatment planning system (TPS). METHODS: A progressive and effective design method for AP of nasopharyngeal carcinoma was realized through automated scripts in this study. A total of 30 patients with nasopharyngeal carcinoma with initial treatment was enrolled. The target coverage, conformity index (CI), homogeneity index (HI), organs at risk sparing, and the efficiency of design and execution were compared between automatic and manual volumetric modulated arc therapy (VMAT) plans. RESULTS: The results of the 2 design methods met the clinical dose requirement. The differences in D95 between the 2 groups in PTV1 and PTV2 showed statistical significance, and the MPs are higher than APs, but the difference in absolute dose was only 0.21% and 0.16%. The results showed that the conformity index of planning target volumes (PTV1, PTV2, PTVnd and PGTVnx+rpn [PGTVnx and PGTVrpn]), homogeneity index of PGTVnx+rpn, and HI of PTVnd in APs are better than that in MPs. For organs at risk, the APs are lower than the MPs, and the difference was statistically significant (P < .05). The manual operation time in APs was 83.21% less than that in MPs, and the computer processing time was 34.22% more. CONCLUSION: IronPython language designed by RayStation TPS has clinical application value in the design of automatic radiotherapy plan for nasopharyngeal carcinoma. The dose distribution of tumor target and organs at risk in the APs was similar or better than those in the MPs. The time of manual operation in the plan design showed a sharp reduction, thus significantly improving the work efficiency in clinical application.

Comparison of the outcomes of stereotactic body radiotherapy versus surgical treatment for elderly (≥70) patients with early-stage non-small cell lung cancer after propensity score matching.

BACKGROUND: The optimal treatment for elderly patients with early-stage non-small cell lung cancer (NSCLC) remains inconclusive. Previous studies have shown that stereotactic body radiotherapy (SBRT) provides encouraging local control though higher incidence of toxicity in elderly than younger populations. The objective of this study was to compare the outcomes of SBRT and surgical treatment in elderly patients with clinical stage I-II NSCLC. METHODS: This retrospective analysis included 205 patients aged ≥70 years with clinical stage I NSCLC who underwent SBRT or surgery at Zhejiang Cancer Hospital (Hangzhou, China) from January 2012 to December 2017. A propensity score matching analysis was performed between the two groups. In addition, we compared outcomes and related toxicity in both study arms. RESULTS: Each group included 35 patients who met the inclusion criteria. Median follow-up was 50.1 (0.8-74.4) months for surgery and 35.5 (11.5-71.4) months for SBRT. The rate of cancer-specific survival was similar between the two treatment arms (p = 0.958). In patients who underwent surgery, the corresponding 3- and 5-year cancer-specific survival rates were 85.3 and 81.7%, respectively. In those who received radiotherapy, these rates were 91.3 and 74.9%, respectively. Moreover, the 3- and 5-year locoregional control in patients who underwent surgery were 90.0 and 80.0%, respectively. In those who received radiotherapy, these rates were 91.1 and 84.1%, respectively. Notably, the observed differences in progression-free survival were not statistically significant (p = 0.934). In the surgery group, grade 1-2 complications were observed in eleven patients (31%). One patient died due to perioperative infection within 30 days following surgery. There was no grade 3-5 toxicity observed in the SBRT group. CONCLUSIONS: The outcomes of surgery and SBRT in elderly patients with early-stage NSCLC were similar.

Comparison of the Efficacy of Stereotactic Body Radiotherapy versus Surgical Treatment for Early-Stage Non-Small Cell Lung Cancer after Propensity Score Matching.

BACKGROUND: The objective of this study was to evaluate the clinical efficacy of stereotactic body radiotherapy (SBRT) and surgical treatment for stage I-II non-small cell lung cancer (NSCLC). METHODS: This retrospective analysis included 879 patients with primary NSCLC who underwent SBRT or surgical treatment in Zhejiang Cancer Hospital, Hangzhou, China from January 2012 to December 2017. RESULTS: Propensity score matching (PSM) analysis was performed between the two groups. Each group included 66 patients who met the inclusion criteria. The median follow-up in the SBRT and surgery groups was 30.8 and 48.4 months, respectively. In the SBRT group, the 1- and 3-year overall survival rates were 98.5 and 83.9%, respectively. In the surgery group, these rates were 98.5 and 89.4%, respectively (P = .248). The 3-year cancer-specific survival rates in the SBRT and surgery groups were 89.1 and 95.2%, respectively (P = .056). CONCLUSIONS: In these propensity score matched early-stage NSCLC patients, the 1- and 3-year overall survival rates associated with SBRT were similar to those observed with surgery. In addition, there was no significant difference in cancer-specific survival between the two groups.