Journal of Radiation Research最新文献

Following the Fukushima Daiichi Nuclear Power Plant accident, Japan enhanced its nuclear disaster preparedness framework. However, personnel shortages stemming from fear and anxiety persist as a critical issue during such disasters. This study investigated the willingness of medical professionals at four university hospitals in Kyushu to participate in nuclear disaster response activities and explored factors influencing this willingness. A cross-sectional web-based survey was conducted among staff at Nagasaki, Kyushu, Saga and Kagoshima University Hospitals. Participants answered 19 questions assessing their willingness to participate in nuclear or radiological emergency response and associated psychosocial and occupational factors. Multiple regression analysis was used to identify predictors of willingness (Q1). A total of 378 valid responses were analyzed. Demographic variables, including age, sex, occupation and disaster experience, did not significantly influence willingness. However, interest in nuclear or radiological emergencies (β =0.383, P < 0.05), Incentives (β =0.249), Family understanding (β =0.116) and Occupational norms (β =0.114) were positively associated with willingness. Conversely, Anxiety (β = -0.151), Expectation of routine training (β = -0.138) and Perceived frequency of nuclear disasters (β = -0.104) were negatively associated with willingness. Medical staff's willingness to respond to nuclear or radiological emergencies is influenced more by psychological and occupational perceptions than by demographic factors. Interventions such as incentive programs, family support initiatives, targeted training and anxiety-reduction strategies may enhance preparedness for and participation in future nuclear or radiological emergencies.

This survey examined the real-world practice of radiotherapy for small-cell lung cancer (SCLC) in Japan, focusing on treatment strategies for limited-disease SCLC (LD-SCLC) and extensive-disease SCLC (ED-SCLC). This study aimed to identify inter-institutional differences, optimize treatment strategies and explore opportunities for standardization. A questionnaire was distributed to members of the Japanese Radiation Oncology Study Group, and responses were collected from 15 December 2023 to 14 March 2024. Responses to 11 questions specifically related to SCLC treatment strategies were analyzed. Among the 112 institutions, 38.3% did not set an upper age limit for concurrent chemoradiotherapy in LD-SCLC, whereas 31.3% set the limit at 80 years. The most commonly used chemotherapy regimen was cisplatin plus etoposide (79.5%), and the predominant radiotherapy fractionation schedule was twice-daily 45 Gy in 30 fractions (97.3%). Elective nodal irradiation (ENI) was ommited in 30.4% of institutions, while 17.9% reported performing ENI in all cases. Intensity-modulated radiation therapy (IMRT) was introduced in 71.4% of institutions, with D50% as the most frequently used dose-prescription method (47.5%). After achieving complete response, 16.1% of institutions routinely perform prophylactic cranial irradiation (PCI) in all patients. Hippocampus-sparing PCI was not widely used at the time of the survey (13.3%). In conclusion, this Japanese nationwide survey highlighted the SCLC treatment patterns and differences compared with non-small lung cancer (NSCLC). ENI omissions and IMRT have become increasingly adopted for SCLC, whereas clinical target volume margin definitions show some variation compared with NSCLC. Regular surveys are essential to monitor the evolution of treatment strategies.

This study aimed to evaluate the clinical validity of a dose-mimicking automated planning for volumetric-modulated arc therapy (VMAT) in patients with stage III non-small cell lung cancer (NSCLC), through direct comparison with a commercial dose volume histogram (DVH)-predicted system. We retrospectively analyzed volumetric-modulated arc therapy plans from 75 patients with stage III NSCLC treated at our institution (60 for training, 15 for testing). The dose-mimicking method was implemented using RatoGuide, and the DVH-predicted method was implemented using RapidPlan. The RatoGuide 3D dose-prediction model was trained on the 60 training cases. For each test case, a predicted dose distribution was generated and converted to a deliverable plan (RGDose) in Eclipse using vendor-provided objective functions. A RapidPlan model trained and generated deliverable plans (RPDose) for the same dataset. The clinical plan dose distribution (CliDose) was the reference. We compared dose distributions and DVH parameters among RGDose, RPDose and CliDose. Mean absolute errors (MAEs) relative to CliDose were 0.83 ± 0.66% (targets) and 2.06 ± 3.14% (organs at risk [OARs]) for RGDose, and 0.88 ± 0.66% (targets) and 2.49 ± 3.63% (OARs) for RPDose. There were no significant differences in OAR DVH parameters between RGDose and CliDose. In contrast, compared to CliDose, RPDose showed a significant reduction in the Esophagus D1cc and a significant increase in the Lungs V5Gy. The dose-mimicking method more faithfully reproduced the original clinical plans than the conventional DVH-predicted system, suggesting that dose-mimicking method can capture complex inter-OAR trade-offs and consistently reflect planner intent.

Boron neutron capture therapy (BNCT) utilizes high linear energy transfer (LET) α-particles and 7Li ions generated through the 10B(n, α)7Li reaction. Precise dosimetry is essential for maximizing therapeutic efficacy while minimizing normal tissue adverse events, considering the microscopic distribution of 10B and cellular structures. Recently, the photon isoeffective dose (DisoE) has been proposed as a more appropriate metric for BNCT treatment planning and can be evaluated using the stochastic microdosimetric kinetic (SMK) model. However, clinical implementation of the SMK model remains challenging due to the difficulty of evaluating its input parameters, which requires computationally intensive radiation transport simulations at the cellular scale. To address this issue, we developed LISMEC (Linear Interpolation System for Stochastic Microdosimetric Kinetic model parameters Evaluated from Cellular-scale simulation), a rapid estimation framework based on precomputed cellular-scale PHITS (Particle and Heavy Ion Transport code System) simulations covering various cell geometries and boron distributions. By applying a linear interpolation algorithm, LISMEC enables the retrieval of SMK model parameters without the need for computationally intensive cellular-scale simulations. The utility of LISMEC, in conjunction with PHITS, was demonstrated through simulations of various irradiation scenarios in reactor-based BNCT. The results showed that DisoE values ranged from 7.4 to 32.7 Gy, even under a fixed macroscopic 10B concentration of 60 ppm. These findings emphasize the importance of incorporating a microscopic distribution of 10B and cellular structures into BNCT treatment planning.

This study evaluated the feasibility of pencil beam scanning (PBS) proton therapy for stereotactic body radiotherapy using an isodose prescription in patients with isolated early-stage lung cancer, comparing dose-volume metrics with those of volumetric modulated arc therapy (VMAT). Treatment plans were generated for 10 patients with tumors located at least 2 cm from the trachea. Each plan prescribed 48 Gy(RBE) in four fractions with a 60% isodose prescription. Both multi-field optimized and single-field optimized PBS plans used four fields, while VMAT plans used two coplanar arcs. Plan robustness was assessed by simulating setup errors of ±5.0 mm and density uncertainties of ±3.5%, with worst-case target coverage also analyzed. Comparisons among the three planning strategies employed Bonferroni-adjusted multiple comparisons for target coverage, robustness, and organ-at-risk doses. PBS achieved target coverage comparable to VMAT, with similar D98% (63.2 ± 1.3 GyRBE vs. 64.0 ± 1.6 Gy; P = 0.12), mean doses (73.2 ± 0.8 GyRBE vs. 73.7 ± 1.2 Gy; P = 0.21), and robustness (D98%: 50.2 ± 0.9 GyRBE vs. 50.3 ± 1.1 Gy; P = 0.77). For the normal lung, PBS significantly reduced low-dose exposure up to V10Gy, whereas VMAT was more effective in reducing doses from V20Gy to the prescription level. All evaluated organ-at-risks received significantly lower mean doses with PBS than with VMAT (P < 0.05). Under a 60% isodose prescription for lung stereotactic body radiotherapy, multi-field optimized-based PBS proton therapy provides target coverage and robustness comparable to VMAT while offering superior normal tissue sparing.

During the coronavirus disease 2019 (COVID-19) pandemic, a short-term decline in radiotherapy use was reported. In this study, we investigated long-term changes in the use of radiotherapy and hypofractionated radiotherapy before and after the COVID-19 pandemic period in Japan and assessed whether the pandemic influenced the adoption of hypofractionation. We obtained data for analysis from the National Database Open Data for fiscal years (FYs) 2014 to 2023. For the 5 years from FY2019 to FY2023, with detailed monthly data available, we used interrupted time series (ITS) analysis to examine changes in the level and slope of claims at the boundaries of the baseline, pandemic and post-pandemic periods. During the 10-year study period, the number of radiotherapy claims increased by an average of 1.6% per year. In FY2020, the peak of the COVID-19 pandemic, the number of radiotherapy claims decreased by 2.0% compared to the previous year. The number of claims for extra fees for hypofractionated radiotherapy for breast and prostate cancer showed a steady increase, except for a temporary decline around the April 2022 policy change in payment requirements for prostate cancer. In the ITS analysis, there were no significant changes in the level and slope of claims for radiotherapy and extra fees for hypofractionated radiotherapy at the onset of the pandemic. In conclusion, the impact of the COVID-19 pandemic on the utilization of radiotherapy in Japan was minimal, and the use of hypofractionated radiotherapy showed a steady increase throughout this period.

The purpose of this study was to design a radiogenomics machine learning-DeepSurv model for biochemical recurrence-free (BCR-free) survival and treatment response (TR) prediction for radiotherapy (RT) of prostate cancer (PCa). In this study, radiomic features were extracted from pre and post treatment multiparametric MRI (mpMRI), including T2-weighted (T2W), diffusion-weighted MR imaging (DWI) and apparent diffusion coefficient (ADC). Also, genomic biomarkers such as Ki-67 (a cell proliferation marker reflecting tumor growth activity and also prognostic information in cancer progression), PTEN (tumor suppressor gene regulating cell growth and survival, have a prominent role for TR and cancer progression) and Decipher (a genomic signature predicting cancer recurrence risk and TR based on gene expression patterns) were collected. Radiomics feature selection and dimensionality reduction methods were employed, followed by training machine learning (ML) models. Moreover, time to event data and survival models including Random Survival Forest (RSF) and DeepSurv neural networks were used. For model performance, the concordance index (C-index) and integrated Brier score (IBS), and for improving interpretability, the SHapley Additive exPlanations (SHAP) were applied. Radiomic feature of MRI including Kurtosis demonstrated a near-perfect positive correlation with Ki-67 expression (r = 0.64), however skewness showed a strong negative correlation with PTEN status (r = -0.88). Entropy and kurtosis of MRI were also highly correlated with the Decipher genomic risk score (r = 0.90 and r = -0.96, respectively). The integrated ML-DeepSurve model performance overall F1-score was 0.93 for TR. The model also offered robust stratification for patients based on BCR-free survival probability. Our findings underscore the potential of radiogenomic signatures as non-invasive biomarkers to personalized PCa RT decisions and provide a novel clinically explainable predictive model based on radiomic and molecular biomarkers for BCR-free survival and TR of mentioned cancer.

The purpose of this study was to evaluate the diffusion of surface-guided radiation therapy (SGRT), implementation of quality control and quality assurance strategies, established clinical workflows and user perceptions regarding the benefits and limitations of SGRT in routine practice. From October to December 2024, we surveyed 880 radiotherapy institutions in Japan regarding institutional characteristics, quality assurance/quality control, computed tomography simulation, treatment procedures and general questions regarding SGRT. The survey was distributed via mailing list and through vendors, and administered via Google Forms. A total of 292 institutions responded, corresponding to a response rate of 33%. Ninety-eight institutions reported introducing SGRT, and 50 institutions had introduced it after 2022. The highest usage rate of SGRT in breast treatment was 87%. Approximately half of the institutions performed daily checks of SGRT and radiation isocenter coincidence, as well as static accuracy, whereas 6% did not perform these checks at all. The primary functions of the SGRT system were patient positioning (94%), respiratory management (78%), patient monitoring (76%) and skin marker-less techniques (69%). Many institutions reduced or eliminated skin marking, citing simplified workflows and reduced setup time. Many respondents observed that SGRT implementation reduced both setup and treatment times for breast/chest, abdomen/pelvis and extremity procedures. SGRT has been widely embraced in Japan, offering notable clinical and workflow benefits. However, because participation in this survey was voluntary, the results may overrepresent institutions with greater awareness or adoption of SGRT. Greater standardization, broader insurance coverage and ongoing technological advancements are essential to fully realize its advantages.

Pelvic radiotherapy for gynecologic malignancies damages the primary active bone marrow reservoir, inducing hematologic toxicity exacerbated by chemotherapy. Optimizing pelvic bone marrow dose-volume constraints is critical to mitigate myelosuppression and maintain treatment efficacy. The present retrospective cohort study analyzed patients with gynecological cancer (n = 61) undergoing concurrent chemoradiotherapy between August 2021 and August 2024. Associations between pelvic bone marrow (PBM) dose-volume parameters and acute hematologic toxicity (AHT) were systematically evaluated. All patients received intensity-modulated radiotherapy encompassing pelvic lymph node regions, with weekly complete blood count monitoring during and for 2 weeks after treatment. The overall incidence of AHT was 70.5% (43/61), with grade ≥ 2 and ≥ 3 AHT occurring in 63.9% (39/61) and 30.0% (14/61) of patients, respectively. Multivariate analysis identified PBM-V15 as an independent predictor of grade ≥ 2 AHT [odds ratio (OR), 2.653; 95% CI, 1.054-6.682; P = 0.038], with an optimal cutoff threshold of 80.44% [area under the curve (AUC), 0.854]. Notably, a lower PBM (LPBM)-V5 specifically predicted grade ≥ 3 AHT (OR, 1.425; 95% CI, 1.022-1.987; P = 0.037), with a threshold of 91.25% (AUC, 0.695). Implementing bone marrow-sparing strategies by restricting PBM-V15 to <80.44% significantly reduced the grade ≥ 2 AHT risk, while a stringent LPBM-V5 constraint (< 91.25%) was pivotal for preventing severe (grade ≥ 3) AHT. These dose-volume parameters should be incorporated into optimization protocols for pelvic radiotherapy in gynecological malignancies.

We have previously reported that the localized application of gaseous plasma to normal tissues suppresses distant tumor growth in mice, resembling the abscopal effect of radiotherapy. Plasma, a partially ionized gas generated by a high-voltage electrical discharge, is fundamentally distinct from ionizing radiation and produces diverse reactive oxygen and nitrogen species that interact with biological tissues. This study examined the abscopal-like effects of normal tissue plasma treatment in BALB/c mice with subcutaneous Colon 26 tumors. The left dorsal skin, 2-3 cm from the tumor, was exposed to plasma for 10 min per day for 5 consecutive days, which delayed the growth of distant tumors. Similar tumor suppression was observed with abdominal exposure, indicating that the effect was not site-specific. In C.B-17 SCID mice (lacking T and B cells) and BALB/c nu/nu mice (lacking T cells), dorsal treatment did not suppress tumor growth, suggesting that T cells are likely involved in the response. Flow cytometric analysis of tumor-infiltrating immune cells in BALB/c mice revealed significant reductions in macrophages and increases in monocytes, with a possible but nonsignificant increase in dendritic cells. No consistent changes were detected in CD8+ T-cell proportion or ICOS (inducible T-cell costimulatory) expression. However, the lack of antitumor effects in immunodeficient mice suggests that CD8+ T cells are involved.