Dose tracking assessment for magnetic resonance guided adaptive radiotherapy of rectal cancers.

BACKGROUND: Magnetic resonance-guided adaptive radiotherapy (MRgART) at MR-Linac allows for plan optimisation on the MR-based synthetic CT (sCT) images, adjusting the target and organs at risk according to the patient's daily anatomy. Conversely, conventional linac image-guided radiotherapy (IGRT) involves rigid realignment of regions of interest to the daily anatomy, followed by the delivery of the reference computed tomography (CT) plan. This study aims to evaluate the effectiveness of MRgART versus IGRT for rectal cancer patients undergoing short-course radiotherapy, while also assessing the dose accumulation process to support the findings and determine its usefulness in enhancing treatment accuracy. METHODS: Nineteen rectal cancer patients treated with a 1.5 Tesla MR-Linac with a prescription dose of 25 Gy (5 Gy x 5) and undergoing daily adapted radiotherapy by plan optimization based on online MR-based sCT images, were included in this retrospective study. For each adapted plan ([Formula: see text]), a second plan ([Formula: see text]) was generated by recalculating the reference CT plan on the daily MR-based sCT images after rigid registration with the reference CT images to simulate the IGRT workflow. Dosimetry of [Formula: see text] and[Formula: see text]was compared for each fraction. Cumulative doses on the first and last fractions were evaluated for both workflows. The dosimetry per single fraction and the cumulative doses were compared using dose-volume histogram parameters. RESULTS: Ninety-five fractions delivered with MRgART were compared to corresponding simulated IGRT fractions. All MRgART fractions fulfilled the target clinical requirements. IGRT treatments did not meet the expected target coverage for 63 out of 94 fractions (67.0%), with 13 fractions showing a V95 median point percentage decrease of 2.78% (range, 1.65-4.16%), and 55 fractions exceeding the V107% threshold with a median value of 15.4 cc (range, 6.0-43.8 cc). For the bladder, the median [Formula: see text] values were 18.18 Gy for the adaptive fractions and 19.60 Gy for the IGRT fractions. Similarly the median [Formula: see text] values for the small bowel were 23.40 Gy and 25.69 Gy, respectively. No statistically significant differences were observed in the doses accumulated on the first or last fraction for the adaptive workflow, with results consistent with the single adaptive fractions. In contrast, accumulated doses in the IGRT workflow showed significant variations mitigating the high dose constraint, nevertheless, more than half of the patients still did not meet clinical requirements. CONCLUSIONS: MRgART for short-course rectal cancer treatments ensures that the dose delivered matches each fraction of the planned dose and the results are confirmed by the dose accumulation process, which therefore seems redundant. In contrast, IGRT may lead to target dose discrepancies and non-compliance with organs at risk constraints and dose accumulation can still highlight notable dosimetric differences.

Comparison of Different Head Tilt Angles in Tomotherapy and Volumetric Modulated Arc Therapy for Hippocampal-Avoidance Whole-Brain Radiotherapy.

PURPOSE: Hippocampal-avoidance whole-brain radiotherapy (HA-WBRT) planning can present challenges. This study examines the influence of head tilt angles on the dosimetric characteristics of target and organs at risk (OARs), aiming to identify the optimal tilt angle that yields optimal dosimetric outcomes using tomotherapy (TOMO). METHODS: Eight patients diagnosed with brain metastases underwent CT scans at five tilt angles: [0°, 10°), [10°, 20°), [20°, 30°), [30°, 40°), and [40°, 45°]. Treatment plans were generated using TOMO and volumetric modulated arc therapy (VMAT). Dosimetric parameters including conformity index (CI), homogeneity index (HI), D2cc, D98%, and Dmean of PTV, as well as Dmax, and Dmean of OARs were analyzed. Furthermore, a comparison was made between the dosimetric parameters of TOMO and VMAT plans. Finally, delivery efficiency of TOMO plans were assessed. RESULTS: For the PTV, [40°, 45°] tilt angle demonstrated significantly better conformity, homogeneity, lower D2cc, and lower Dmean for the PTV. Regarding the OARs, the [40°, 45°] head tilt angle demonstrated significantly lower Dmax and Dmean in hippocampus, eyes, optic chiasm, and optic nerves. The [40°, 45°] tilt angle also showed significantly lower Dmax for brainstem and cochleas, as well as a lower Dmean for lens. In the [40°,45°] tilt angle for HA-WBRT, TOMO showed superior performance over VMAT for the PTV. TOMO achieved lower Dmax for brainstem, cochleas, optic nerves, and optic chiasm, as well as a lower Dmean for hippocampus. Furthermore, a significant correlation was found between delivery time and the PTV projection length in the sagittal plane. CONCLUSION: The TOMO plan utilizing a tilt angle range of [40°, 45°] demonstrated superior PTV conformity and uniformity, along with enhanced OARs sparing. Furthermore, it exhibited a dosimetric advantage over VMAT for PTV and most OARs at the same angle range.

T lymphocyte and neutrophil/lymphocyte ratio in patients with radiation-induced oral mucositis after intensity-modulated radiation therapy for head and neck cancer: A retrospective single-center study.

To investigate T lymphocyte, neutrophil/lymphocyte ratio (NLR) and their impact on patients with radiation-induced oral mucositis (RIOM) after intensity-modulated radiotherapy for head and neck cancer. The clinical data of 148 patients diagnosed with head and neck cancer from January 2016 to January 2019 were retrospectively analyzed. Patients were divided into RIOM group (n = 42 cases) and non-RIOM group (n = 106 cases), based on whether they developed RIOM after intensity-modulated radiation therapy. The T lymphocyte and NLR of the 2 groups were analyzed before and after treatment; The correlation between T lymphocyte and NLR in RIOM group was analyzed. We used RTOG grading system to evaluate and scale the RIOM. The relationship between the grade of RIOM, T lymphocyte and NLR in RIOM group was analyzed. After treatment, the proportion of CD3 +, CD4 +, and CD8 + T lymphocytes in the 2 groups after treatment were decreased, and the RIOM group was significantly lower than non-RIOM group, P < .05. NLR in RIOM group was significantly higher than that in non-RIOM group, P < .05. The data of overall survival showed no significant differences between 2 groups (HR = 0.82, 95% CI: 0.43-1.59). Compared with RIOM group, patients in non-RIOM group showed a longer progress-free survival (HR = 0.57, 95% CI: 0.33-0.99). In RIOM group, NLR was negatively correlated with CD3 + (r = -0.433, P = .004), CD4 + (r = -0.644, P < .001) and CD8 + T cells (r = -0.665, P < .001). RIOM was positively correlated with NLR (R = 0.621, P < .001), negatively correlated with CD4 + T cell ratio (r = -0.449, P = .003) and CD8 + T cell ratio (r = -0.307, P = .048), but RIOM did not correlate with CD3 + T cell ratio (r = -0.225, P = .152). For patients with RIOM after intensity-modulated radiotherapy for head and neck cancer, T lymphocyte showed a downward trend, and NLR showed an upward trend. In addition, T lymphocyte and NLR are closely related to the RIOM, indicating that clinicians should be aware of the importance of T lymphocyte and NLR on patients received radiotherapy.

Delineation of the "Oropharyngeal Mucosa" and Limiting its Dose in Head and Neck Cancer Patients Spares the Oropharynx Without Compromising Target Coverage.

OBJECTIVES: Radiation-induced oropharyngeal injury is a dose-limiting toxicity in head and neck cancer patients. Delineation of the "oropharyngeal mucosa" and limiting its dose to spare the oropharynx was investigated. METHODS: In this retrospective study, computed tomography imaging from eight patients with previously untreated head and neck cancer was employed. An adaptive contouring brush within the planning software Monaco was used to create an air cavity within the oropharynx, and then the air cavity was expanded uniformly 2 mm to create the "oropharyngeal mucosa". Three plans were independently generated for each patient: Plan1: dose constraint was applied for the oropharynx; Plan2: dose constraints were applied for the oropharynx and the "oropharyngeal mucosa"; Plan3: dose constraint was applied for the "oropharyngeal mucosa". T-tests were used to compare the dosimetry variables. RESULTS: All plans had adequate target coverage and there were no statistical differences among plans. The mean dose, D30%, D45%, D50%, D85%, D90%, D95%, D100%, V25 Gy, V30 Gy, V35 Gy, V40 Gy, and V45 Gy of the oropharynx and "oropharyngeal mucosa" in Plan1 were significantly higher than those in Plan2 and Plan3. There were no significant differences between Plan2 and Plan3. There were no significant differences in the dosimetric parameters of any other organs at risk. CONCLUSION: Delineation of the "oropharyngeal mucosa" and limiting its dose should be an easy and effective method to spare the oropharynx.

Radiation-induced oropharyngeal injury is dose-limiting toxicity in head and neck cancer patients. Delineation of "oropharyngeal mucosa" and limiting its dose should be an easy and effective method to spare the oropharynx.

Impact of interplay effects on spot scanning proton therapy with motion mitigation techniques for lung cancer: SFUD versus robustly optimized IMPT plans utilizing a four-dimensional dynamic dose simulation tool.

BACKGROUND: The interaction between breathing motion and scanning beams causes interplay effects in spot-scanning proton therapy for lung cancer, resulting in compromised treatment quality. This study investigated the effects and clinical robustness of two types of spot-scanning proton therapy with motion-mitigation techniques for locally advanced non-small cell lung cancer (NSCLC) using a new simulation tool (4DCT-based dose reconstruction). METHODS: Three-field single-field uniform dose (SFUD) and robustly optimized intensity-modulated proton therapy (IMPT) plans combined with gating and re-scanning techniques were created using a VQA treatment planning system for 15 patients with locally advanced NSCLC (70 GyRBE/35 fractions). In addition, gating windows of three or five phases around the end-of-expiration phase and two internal gross tumor volumes (iGTVs) were created, and a re-scanning number of four was used. First, the static dose (SD) was calculated using the end-of-expiration computed tomography (CT) images. The four-dimensional dynamic dose (4DDD) was then calculated using the SD plans, 4D-CT images, and the deformable image registration technique on end-of-expiration CT. The target coverage (V98%, V100%), homogeneity index (HI), and conformation number (CN) for the iGTVs and organ-at-risk (OAR) doses were calculated for the SD and 4DDD groups and statistically compared between the SD, 4DDD, SFUD, and IMPT treatment plans using paired t-test. RESULTS: In the 3- and 5-phase SFUD, statistically significant differences between the SD and 4DDD groups were observed for V100%, HI, and CN. In addition, statistically significant differences were observed for V98%, V100%, and HI in phases 3 and 5 of IMPT. The mean V98% and V100% in both 3-phase plans were within clinical limits (> 95%) when interplay effects were considered; however, V100% decreased to 89.3% and 94.0% for the 5-phase SFUD and IMPT, respectively. Regarding the significant differences in the deterioration rates of the dose volume histogram (DVH) indices, the 3-phase SFUD plans had lower V98% and CN values and higher V100% values than the IMPT plans. In the 5-phase plans, SFUD had higher deterioration rates for V100% and HI than IMPT. CONCLUSIONS: Interplay effects minimally impacted target coverage and OAR doses in SFUD and robustly optimized IMPT with 3-phase gating and re-scanning for locally advanced NSCLC. However, target coverage significantly declined with an increased gating window. Robustly optimized IMPT showed superior resilience to interplay effects, ensuring better target coverage, prescription dose adherence, and homogeneity than SFUD. TRIAL REGISTRATION: None.

Efficacy and safety of MR-guided adaptive simultaneous integrated boost radiotherapy to primary lesions and positive lymph nodes in the neoadjuvant treatment of locally advanced rectal cancer: a randomized controlled phase III trial.

BACKGROUND: In locally advanced rectal cancer (LARC), optimizing neoadjuvant strategies, including the addition of concurrent chemotherapy and dose escalation of radiotherapy, is essential to improve tumor regression and subsequent implementation of anal preservation strategies. Currently, dose escalation studies in rectal cancer have focused on the primary lesions. However, a common source of recurrence in LARC is the metastasis of cancer cells to the proximal lymph nodes. In our trial, we implement simultaneous integrated boost (SIB) to both primary lesions and positive lymph nodes in the experimental group based on magnetic resonance-guided adaptive radiotherapy (MRgART), which allows for more precise (and consequently intense) targeting while sparing neighboring healthy tissue. The objective of this study is to evaluate the efficacy and safety of MRgART dose escalation to both primary lesions and positive lymph nodes, in comparison with the conventional radiotherapy of long-course concurrent chemoradiotherapy (LCCRT) group, in the neoadjuvant treatment of LARC. METHODS: This is a multi-center, randomized, controlled phase III trial (NCT06246344). 128 patients with LARC (cT3-4/N+) will be enrolled. During LCCRT, patients will be randomized to receive either MRgART with SIB (60-65 Gy in 25-28 fractions to primary lesions and positive lymph nodes; 50-50.4 Gy in 25-28 fractions to the pelvis) or intensity-modulated radiotherapy (50-50.4 Gy in 25-28 fractions). Both groups will receive concurrent chemotherapy with capecitabine and consolidation chemotherapy of either two cycles of CAPEOX or three cycles of FOLFOX between radiotherapy and surgery. The primary endpoints are pathological complete response (pCR) rate and surgical difficulty, while the secondary endpoints are clinical complete response (cCR) rate, 3-year and 5-year disease-free survival (DFS) and overall survival (OS) rates, acute and late toxicity and quality of life. DISCUSSION: Since dose escalation of both primary lesions and positive nodes in LARC is rare, we propose conducting a phase III trial to evaluate the efficacy and safety of SIB for both primary lesions and positive nodes in LARC based on MRgART. TRIAL REGISTRATION: The study was registered at ClinicalTrials.gov with the Identifier: NCT06246344 (Registered 7th Feb 2024).

Radiotherapy with S-1 for the treatment of esophageal squamous cell carcinoma 75 years or older.

OBJECTIVE: Explore the efficacy and safety of involved-field irradiation (IFI) combined with S-1 as definitive concurrent chemoradiotherapy (dCRT) for locally advanced elderly esophageal squamous cell carcinoma (ESCC), under the premise of intensity-modulated radiotherapy (IMRT). METHODS: We designed a prospective single-arm phase II study. The study enrolled 91 patients aged 75 to 92 years. Eligible participants had histologically confirmed squamous cell carcinoma, stage II to IV disease based on the 8th edition of the American Joint Committee on Cancer (AJCC). All elderly patients (EPs) received dCRT with S-1. which was administered orally twice daily for 28 days. The radiotherapy dose was 61.2 Gy delivered in 34 fractions or 50.4 Gy delivered in 28 fractions. The primary endpoint was 2-year overall survival (OS), and the secondary endpoints were progression-free survival (PFS), local control rate (LCR), and safety. RESULTS: From July 2017 to July 2021, we enrolled EPs with ESCC who were treated at the Jiangsu Cancer hospital. As of August 1, 2023, the median follow-up of surviving EPs was 31.4 months (IQR: 25.2 to 72.6 months). 83 patients (91.2%) completed the whole course of treatment. The 2-year OS rate was 59.2%, and the PFS rate was 43.7%. The most common grade 1 to 2 adverse effects (AEs) were radiation esophagitis (79.1%), and then were radiation pneumonia (46.2%). Anemia (41.8%) was the most common of grade 1 to 2 hematologic toxicity. The incidence of grade 3 or above AEs was 24.2%, and the incidence of leukopenia was the highest (11.0%). There was not one death due to treatment-related toxicity. In a subgroup analysis of radiotherapy doses, we found no statistically significant differences in PFS (P = 0.465) and OS (P = 0.345) in EPs with ESCC who received 50.4 Gy and 61.2 Gy, and that patients in the 50.4 Gy group had lower dermatitis (P = 0.045) and anemia (P = 0.004). CONCLUSIONS: IF-IMRT combined with S-1 is a promising regimen for elderly ESCC. And the radiotherapy dose of 50.4 Gy remains the standard dose for EPs with ESCC undergoing CCRT.

Radiotherapy for recurrent juvenile nasopharyngeal angiofibroma.

Juvenile nasopharyngeal angiofibroma (JNA) is a rare paediatric tumour known for its local destructiveness and high recurrence rate. Surgery is the primary treatment modality for JNA, though other options, such as hormonal therapy, embolisation and radiotherapy, exist for inoperable cases. The location of the tumour makes surgical intervention challenging. A 14-year-old male presented with epistaxis and headaches as the chief complaints and was diagnosed with nasopharynx angiofibroma by computed tomography (CT) scan in 2018. Pre-operative embolisation was performed and followed by surgical removal of a 4 cm tumour in January 2019. Pathological examination revealed CD34 positivity, S100 negativity and Ki-67 positivity (5 to 10%), confirming angiofibroma. In October 2019, a 3.6 cm recurrent tumour was treated with embolisation and a second surgery. Pathological findings again confirmed JNA. The patient underwent four surgeries in total, but epistaxis persisted. In 2021, local radiotherapy was administered using intensity-modulated radiation therapy (IMRT) at a dose of 60 Gy in 25 fractions. Serial magnetic resonance imaging (MRI) post-radiotherapy showed a decreasing tumour size, with no further epistaxis and no observed radiation side effects 2 years post-treatment. Radiation therapy remains a strong alternative for managing recurrent JNA.

Bone marrow toxicity in patients with locally advanced cervical cancer undergoing multimodal treatment with VMAT/IMRT: are there dosimetric predictors for toxicity?

PURPOSE: For women with locoregionally advanced cervical cancer, the standard of care treatment is the curatively intended chemoradiation therapy (CRT). A relationship between bone marrow (BM) dose-volume histograms (DVHs) and acute hematological toxicity (HT) has been debated recently. Aim of this study was the evaluation of BM dose constraints and HT in a contemporary patient cohort. METHODS: Radiation treatment plans of 31 patients with cervical cancer (FIGO stage IIB-IVB) treated with intensity-modulated radiotherapy and simultaneous chemotherapy were explored retrospective. Pelvic bones (PB) and femoral heads (FH) were contoured and DVHs were correlated with white blood cells (WBC), hemoglobin levels and platelets. RESULTS: Comparing the absolute blood levels with the dose volumes of both FH and PB the data showed a significant correlation between WBC and the median dose of the FH and the median dose, V30Gy, V40Gy and V50Gy of the PB. A correlation between the toxicity grade of anemia and mean dose, maximum dose and V5Gy of the PB was found. Counting the highest grade of HT of all three blood levels of each patient, significant correlations were found for the mean and median dose, V30Gy, V40Gy and V50Gy of the PB. CONCLUSION: The results show that blood levels may correlate with distinct dosimetric subvolumes of critical bone marrow compartments with a potential impact on therapeutic outcome and treatment-related toxicity. The data presented are in line with the previous findings on the relevance of dosimetric exposure of pelvic bony subvolumes.

3D printed heterogeneous paediatric head and adult thorax phantoms for linear accelerator radiotherapy quality assurance: from fabrication to treatment delivery.

Objective. This study aims to design and fabricate a 3D printed heterogeneous paediatric head phantom and to customize a thorax phantom for radiotherapy dosimetry.Approach. This study designed, fabricated, and tested 3D printed radiotherapy phantoms that can simulate soft tissue, lung, brain, and bone. Various polymers were considered in designing the phantoms. Polylactic acid+, nylon, and plaster were used in simulating different tissue equivalence. Dimensional accuracy, and CT number were investigated. The phantoms were subjected to a complete radiotherapy clinical workflow. Several treatment plans were delivered in both the head and the thorax phantom from a simple single 6 MV beam, parallel opposed beams, and five-field intensity modulated radiotherapy (IMRT) beams. Dose measurements using an ionization chamber and radiochromic films were compared with the calculated doses of the Varian Eclipse treatment planning system (TPS).Main results. The fabricated heterogeneous phantoms represent paediatric human head and adult thorax based on its radiation attenuation and anatomy. The measured CT number ranges are within -786.23 ± 10.55, 0.98 ± 3.86, 129.51 ± 12.83, and 651.14 ± 47.76 HU for lung, water/brain, soft tissue, and bone, respectively. It has a good radiological imaging visual similarity relative to a real human head and thorax depicting soft tissue, lung, bone, and brain. The accumulated dose readings for both conformal radiotherapy and IMRT match with the TPS calculated dose within ±2% and ±4% for head and thorax phantom, respectively. The mean pass rate for all the plans delivered are above 90% for gamma analysis criterion of 3%/3 mm.Significance and conclusion. The fabricated heterogeneous paediatric head and thorax phantoms are useful in Linac end-to-end radiotherapy quality assurance based on its CT image and measured radiation dose. The manufacturing and dosimetry workflow of this study can be utilized by other institutions for dosimetry and trainings.

A retrospective study on the effectiveness of intensity modulated radiation therapy for thyroid associated ophthalmopathy at a single institute.

Thyroid-associated ophthalmopathy (TAO) is a hallmark autoimmune condition, and the treatment of TAO requires a multidisciplinary approach. Radiation therapy (RT) is a viable treatment option for active TAO, IMRT is a more precise technology in radiation oncology. This study aims to evaluate the efficacy, feasibility, and safety of orbital intensity-modulated radiation therapy (IMRT) in the treatment of TAO. A single-center retrospective analysis was conducted, including patients diagnosed with moderate to severe active TAO at the Department of Radiation Oncology, Peking University Third Hospital, from October 2020 to October 2023, who had poor responses to corticosteroid treatment. These patients subsequently received IMRT treatment, followed by a period of follow-up and retrospective analysis. The study focused on the outcomes of treatment efficacy, safety, and acute toxic reactions induced by radiation therapy. Improvements in clinical activity score (CAS) at 4 and 12 months were considered as primary and secondary study endpoints, respectively, along with the incidence rate of adverse events. The median follow-up period was 12 months. The median follow-up time after radiation therapy was 12 months. There was no statistically significant difference in CAS between before and 4 months after radiation therapy (CAS: 5.53 ± 2.07 vs.4.68 ± 2.62; R squared: 0.21; 95% CI: - 1.01-0.02; P = 0.054). However, there was a significant reduction in CAS 12 months post-treatment compared to pre-treatment (CAS: 5.53 ± 2.07 vs. 3.06 ± 2.38; R squared: 0.66; 95% CI: 3.42 - 1.52; P < 0.001). The CAS showed a progressively decreasing trend at both 4 months and 12 months post-treatment. In the combined radiotherapy with glucocorticoid treatment group, a statistically significant difference was found between the CAS before treatment and 12 months after radiotherapy (CAS: 6.38 ± 2.00 vs. 3.88 ± 2.85; R squared: 0.66; 95% CI - 4.11 to 0.89; P = 0.008). In the radiotherapy alone group, a statistically significant difference was found between the CAS before treatment and 12 months after radiotherapy (CAS: 4.78 ± 1.92 vs. 2.33 ± 1.73; R squared: 0.66; 95% CI - 3.89 to 1.00; P = 0.005). A few patients experienced Grade I periorbital edema, conjunctival congestion, and dry eye syndrome, but no adverse events such as cataracts, radiation retinopathy, or radiation-induced optic neuropathy were observed by the end of the follow-up period. Orbital IMRT is an effective treatment modality for moderate to severe active TAO, demonstrating significant efficacy even in patients who had not achieved success with previous treatments such as corticosteroids. This retrospective study was approved by the Ethics Committee of Peking University Third Hospital. The permit number was M2024220 and data of registration was April I, 2024.

Failure patterns and individualized treatment plans of reirradiation for inoperable locally recurrent nasopharyngeal carcinoma.

Re-irradiation with intensity-modulated radiotherapy (IMRT) remains the primary treatment modality for inoperable locally recurrent nasopharyngeal carcinoma (NPC). However, the rate of radiation-related late adverse effects is often substantially high. Therefore, we aimed to explore failure patterns and individualized treatment plans of re-irradiation for inoperable locally recurrent NPC. Ninety-seven patients who underwent IMRT were retrospectively analyzed. Sixty-two patients had clinical target volume of recurrence (rCTV) delineated, and thirty-five patients had only gross tumor volume of recurrence (rGTV) delineated. Twenty-nine patients developed second local failures after re-irradiation with IMRT (28 cases available). Among those patients, 64.3% (18/28) of patients and 35.7% (10/28) developed in-field or out-field, respectively. No statistical correlation was observed between target volume (rGTV or rCTV) and the local recurrence rate, local failure patterns, grade ≥ 3 toxicity, and survival. Multivariate analysis showed that recurrent T (rT) stage (HR 2.62, P = 0.019) and rGTV volume (HR 1.73, P = 0.037) were independent prognostic factors for overall survival (OS). Risk stratification based on rT stage and rGTV volume revealed that low risk group had a longer 3-year OS rate (66.7% vs. 23.4%), lower total grade ≥ 3 toxicity (P = 0.004), and lower re-radiation associated mortality rates (HR 0.45, P = 0.03) than high risk group. This study demonstrates that the delineation of rCTV may not be beneficial for re-irradiation using IMRT in locally recurrent NPC. Patients with low risk were most suitable for re-irradiation, with maximizing local salvage and minimizing radiation-related toxicities. More precise and individualized plans of re-irradiation are warranted.

Clinical implementation and evaluation of deep learning-assisted automatic radiotherapy treatment planning for lung cancer.

PURPOSE: The purpose of the study is to investigate the clinical application of deep learning (DL)-assisted automatic radiotherapy planning for lung cancer. METHODS: A DL model was developed for predicting patient-specific doses, trained and validated on a dataset of 235 patients with diverse target volumes and prescriptions. The model was integrated into clinical workflow with DL-predicted objective functions. The automatic plans were retrospectively designed for additional 50 treated manual volumetric modulated arc therapy (VMAT) plans. A comparison was made between automatic and manual plans in terms of dosimetric indexes, monitor units (MUs) and planning time. Plan quality metric (PQM) encompassing these indexes was evaluated, with higher PQM values indicating superior plan quality. Qualitative evaluations of two plans were conducted by four reviewers. RESULTS: The PQM score was 40.7 ± 13.1 for manual plans and 40.8 ± 13.5 for automatic plans (P = 0.75). Compared to manual plans, the targets coverage and homogeneity of automatic plans demonstrated no significant difference. Manual plans exhibited better sparing for lung in V5 (difference: 1.8 ± 4.2 %, P = 0.02), whereas automatic plans showed enhanced sparing for heart in V30 (difference: 1.4 ± 4.7 %, P = 0.02) and for spinal cord in Dmax (difference: 0.7 ± 4.7 Gy, P = 0.04). The planning time and MUs of automatic plans were significantly reduced by 70.5 ± 20.0 min and 97.4 ± 82.1. Automatic plans were deemed acceptable in 88 % of the reviews (176/200). CONCLUSIONS: The DL-assisted approach for lung cancer notably decreased planning time and MUs, while demonstrating comparable or superior quality relative to manual plans. It has the potential to provide benefit to lung cancer patients.

Impact of 1.5†T Magnetic Field on Treatment Plan Quality in MR-Guided Radiotherapy: Typical Phantom Test Cases.

PURPOSE: This study aims to investigate the influence of the magnetic field on treatment plan quality using typical phantom test cases, which encompass a circle target test case, AAPM TG119 test cases (prostate, head-and-neck, C-shape, multi-target test cases), and a lung test case. MATERIALS AND METHODS: For the typical phantom test cases, two plans were formulated. The first plan underwent optimization in the presence of a 1.5 Tesla magnetic field (1.5 T plan). The second plan was re-optimized without a magnetic field (0 T plan), utilizing the same optimization conditions as the first plan. The two plans were compared based on various parameters, including con-formity index (CI), homogeneity index (HI), fit index (FI) and dose coverage of the planning target volume (PTV), dose delivered to organs at risk (OARs) and normal tissue (NT), monitor unit (MU). A plan-quality metric (PQM) scoring procedure was employed. For the 1.5 T plans, dose verifications were performed using an MR-compatible ArcCHECK phantom. RESULTS: A smaller dose influence of the magnetic field was found for the circle target, prostate, head-and-neck, and C-shape test cases, compared with the multi-target and lung test cases. In the multi-target test case, the significant dose influence was on the inferior PTV, followed by the superior PTV. There was a relatively large dose influence on the PTV and OARs for lung test case. No statistically significant differences in PQM and MUs were observed. For the 1.5 T plans, gamma passing rates were all higher than 95% with criteria of 2 mm/3% and 2 mm/2%. CONCLUSION: The presence of a 1.5 T magnetic field had a relatively large impact on dose parameters in the multi-target and lung test cases compared with other test cases. However, there were no significant influences on the plan-quality metric, MU and dose accuracy for all test cases.

Charged particle radiotherapy for thyroid cancer. A systematic review.

The role of external beam radiotherapy (EBRT) in thyroid cancer (TC) remains contentious due to limited data. Retrospective studies suggest adjuvant EBRT benefits high-risk differentiated thyroid cancer (DTC) and limited-stage anaplastic thyroid carcinoma (ATC), enhancing locoregional control and progression-free survival when combined with surgery and chemotherapy. Intensity-modulated radiotherapy (IMRT) and particle therapy (PT), including protons, carbon ions, and Boron Neutron Capture Therapy (BNCT), represent advances in TC treatment. Following PRISMA guidelines, we reviewed 471 studies from January 2002 to January 2024, selecting 14 articles (10 preclinical, 4 clinical). Preclinical research focused on BNCT in ATC mouse models, showing promising local control rates. Clinical studies explored proton, neutron, or photon radiotherapy, reporting favorable outcomes and manageable toxicity. While PT shows promise supported by biological rationale, further research is necessary to clarify its role and potential combination with systemic treatments in TC management.

Comparative analysis of delivered and planned doses in target volumes for lung stereotactic ablative radiotherapy.

BACKGROUND: Adaptive therapy has been enormously improved based on the art of generating adaptive computed tomography (ACT) from planning CT (PCT) and the on-board image used for the patient setup. Exploiting the ACT, this study evaluated the dose delivered to patients with non-small-cell lung cancer (NSCLC) patients treated with stereotactic ablative radiotherapy (SABR) and derived relationship between the delivered dose and the parameters obtained through the evaluation procedure. METHODS: SABR treatment records of 72 patients with NSCLC who were prescribed a dose of 60 Gy (Dprescribed) to the 95% volume of the planning target volume (PTV) in four fractions were analysed in this retrospective study; 288 ACTs were generated by rigid and deformable registration of a PCT to a cone-beam computed tomography (CBCT) per fraction. Each ACT was sent to the treatment planning system (TPS) and treated as an individual PCT to calculate the dose. Delivered dose to a patient was estimated by averaging four doses calculated from four ACTs per treatment. Through the process, each ACT provided the geometric parameters, such as mean displacement of the deformed PTV voxels (Warpmean) and Dice similarity coefficient (DSC) from deformation vector field, and dosimetric parameters, e.g. difference of homogeneity index (ΔHI, HI defined as (D2%-D98%)/Dprescribed*100) and mean delivered dose to the PTV (Dmean), obtained from the dose statistics in the TPS. Those parameters were analyzed using multiple linear regression and one-way-ANOVA of SPSS® (version 27). RESULTS: The prescribed dose was confirmed to be fully delivered to internal target volume (ITV) within maximum difference of 1%, and the difference between the planned and delivered doses to the PTV was agreed within 6% for more than 95% of the ACT cases. Volume changes of the ITV during the treatment course were observed to be minor in comparison of their standard deviations. Multiple linear regression analysis between the obtained parameters and the dose delivered to 95% volume of the PTV (D95%) revealed four PTV parameters [Warpmean, DSC, ΔHI between the PCT and ACT, Dmean] and the PTV D95% to be significantly related with P-values < 0.05. The ACT cases of high ΔHI were caused by higher values of the Warpmean and DSC from the deformable image registration, resulting in lower PTV D95% delivered. The mean values of PTV D95% and Warpmean showed significant differences depending on the lung lobe where the tumour was located. CONCLUSIONS: Evaluation of the dose delivered to patients with NSCLC treated with SABR using ACTs confirmed that the prescribed dose was accurately delivered to the ITV. However, for the PTV, certain ACT cases characterised by high HI deviations from the original plan demonstrated variations in the delivered dose. These variations may potentially arise from factors such as patient setup during treatment, as suggested by the statistical analyses of the parameters obtained from the dose evaluation process.

Effect analysis of 847 nasopharyngeal carcinoma cases treated with intensity modulated radiation: Experience and suggestions.

OBJECTIVES: To identify the failure patterns and prognostic factors of nonmetastatic nasopharyngeal carcinoma (NPC) in the intensity-modulated radiotherapy (IMRT) era. METHODS: Data on 847 patients with newly diagnosed, non-disseminated NPC treated by IMRT between 2012 and 2016 were retrospectively reviewed. Survival outcome, failure patterns and prognosis factors were analyzed. RESULTS: The 5-year local relapse-free survival, nodal relapse-free survival, distant metastasis-free survival, disease-free survival, and overall survival rates were 94.3%, 95.3%, 84.8%, 76.5% and 85.7%, respectively. The major local recurrence sites were the nasopharynx (91.5%, 43/47) and skull base (68.1%, 32/47); 39 patients had in-field failures, four had marginal failures, and four had out-field failures. Level IIb (62.2%, 23/37) was the most frequent regional recurrence site, followed by IIa (35.1%, 13/37) and retropharyngeal region (32.4%, 12/37); 35 cases had in-field failure alone, one had out-field failure alone, and one had both in- and out-field failure. TNM stage was the most significant factor for prognosis prediction. 402 (47.5%) patients had acute adverse events of grade 3 or 4; leukopenia (31.5%) and mucositis (26.7%) was the most common hematological and non-hematological event, respectively. Late complications were slight or moderate damages; xerostomia (647/847, 76.4%) and hearing impairment (422/847, 49.8%) remained the most troublesome. CONCLUSION: NPC patients treated with IMRT obtained satisfactory survival outcomes. The key failure pattern was distant metastasis. The main pattern of local-regional failure was in-field failure. Screening high risk patients with distant metastases and optimizing radiotherapy targets should be studied.

Deep learning for patient-specific quality assurance of volumetric modulated arc therapy: Prediction accuracy and cost-sensitive classification performance.

PURPOSE: To evaluate a deep learning model's performance in predicting and classifying patient-specific quality assurance (PSQA) results for volumetric modulated arc therapy (VMAT), aiming to streamline PSQA workflows and reduce the onsite measurement workload. METHODS: A total of 761 VMAT plans were analyzed using 3D-MResNet to process multileaf collimator images and monitor unit data, with the gamma passing rate (GPR) as the output. Thresholds for the predicted GPR (Th-p) and measured GPR (Th-m) were established to aid in PSQA decision-making, using cost curves and error rates to assess classification performance. RESULTS: The mean absolute errors of the model for the test set were 1.63 % and 2.38 % at 3 %/2 mm and 2 %/2 mm, respectively. For the classification of the PSQA results, Th-m was 88.3 % at 2 %/2 mm and 93.3 % at 3 %/2 mm. The lowest cost-sensitive error rates of 0.0127 and 0.0925 were obtained when Th-p was set as 91.2 % at 2 %/2 mm and 96.4 % at 3 %/2 mm, respectively. Additionally, the 2 %/2 mm classifier also achieved a lower total expected cost of 0.069 compared with 0.110 for the 3 %/2 mm classifier. The deep learning classifier under the 2 %/2 mm gamma criterion had a sensitivity and specificity of 100 % (10/10) and 83.5 % (167/200), respectively, for the test set. CONCLUSIONS: The developed 3D-MResNet model can accurately predict and classify PSQA results based on VMAT plans. The introduction of a deep learning model into the PSQA workflow has considerable potential for improving the VMAT PSQA process and reducing workloads.