Gold nanoparticles (AuNPs) can be used with megavolt (MV) X-rays to exert radiosensitization effects, as demonstrated in cell survival assays and mouse experiments. However, the detailed mechanisms are not clear; besides physical dose enhancement, several chemical and biological processes have been proposed. Reducing the AuNP concentration while achieving sufficient enhancement is necessary for the clinical application of AuNPs. Here, we used positively charged (+) AuNPs to determine the radiosensitization effects of AuNPs combined with MV X-rays on DNA damage in vitro. We examined the effect of low concentrations of AuNPs on DNA damage and reactive oxygen species (ROS) generation. DNA damage was promoted by 1.4 nm +AuNP with dose enhancement factors of 1.4 ± 0.2 for single-strand breaks and 1.2 ± 0.1 for double-strand breaks. +AuNPs combined with MV X-rays induced radiosensitization at the DNA level, indicating that the effects were physical and/or chemical. Although −AuNPs induced similar ROS levels, they did not cause considerable DNA damage. Thus, dose enhancement by low concentrations of +AuNPs may have occurred with the increase in the local +AuNP concentration around DNA or via DNA binding. +AuNPs showed stronger radiosensitization effects than −AuNPs. Combining +AuNPs with MV X-rays in radiation therapy may improve clinical outcomes.

This study compared the pain response to palliative radiotherapy for bone metastases and non-bone lesions based on the International Consensus on Palliative Radiotherapy Effectiveness (ICPRE) criteria. This two-cohort study used data from a prospective cohort of 867 registered lesions from 500 patients conducted between August 2021 and September 2023. Pain responses were assessed using the ICPRE criteria at prespecified timings of 2, 4, 12, 24, 36, and 52 weeks. The primary outcome was the pain response rate within 12 weeks, comparing two groups of patients with bone and non-bone lesions. A multivariate logistic regression analysis was conducted to adjust for confounding covariates based on opioid use, irradiation history, performance status, NRS, primary disease, and radiation dose. Among 678 lesions from 440 patients who met the criteria, 541 (80 %) and 137 (20 %) were in the bone and non-bone cohort, including primary tumors, lymph node metastases, and others. The mean age was 63 years, and 45 % were female. Treatment included conventional radiotherapy of a single 8 Gy dose, 20 Gy in 5 fractions, and 30 Gy in 10 fractions, used in 89 % of lesions. While opioid use (67 %) and re-irradiation rates (22 %) were not different between cohorts, the non-bone cohort had shorter median survival (4.9 months vs. 6.3 months, P = 0.017) and more frequently fractionated irradiation (85 % vs. 67 %, P < 0.001). No differences were observed in pain response rates between the two groups (57 % vs. 62 %, P = 0.33), which remained consistent after adjusting covariates. Re-irradiation and opioid were associated with negative impacts on pain response in the bone cohort. In contrast, the increased irradiation dose was identified as potentially affecting the non-bone cohort. This study suggested palliative radiotherapy is effective for painful non-bone lesions and potential dose-dependency for pain response, highlighting the need for future randomized controlled trials to determine the optimal radiation dose.

Background: This study aimed to investigate preoperative spirometry and BMI as early predictors of the mean heart and lung dose (MHD, MLD) in deep inspiration breath-hold (DIBH) radiotherapy. Methods: Left-sided breast cancer patients underwent breast-conserving surgery followed by DIBH radiotherapy enrolled. Patients who were not available for preoperative spirometry were excluded. One hundred eligible patients were performed free-breathing (FB-) CT and DIBH-CT for plan comparison. We completed the correlative and multivariate analysis to develop the linear regression models for dose prediction. The residuals were calculated to explore the unpreferable subgroups and compare the prediction accuracy. Results: Among the parameters, vital capacity (VC) and BMI showed the strongest negative correlation with MHD (r = − 0.33) and MLD (r = − 0.34), respectively. They were also significant in multivariate analysis (P < 0.001). Elderly and less VC were independent predictors of increasing absolute residuals (AR). The VC model showed no significant difference in AR compared to the model using the CT parameter of lung volume in FB (LV-FB): median AR of the LV-FB model vs. the VC model was 0.12 vs. 0.11 Gy (P = 0.79). On the other hand, the median AR of the MLD model was 0.38 Gy, showing no specific subgroups of larger AR. Conclusion: Preoperative spirometry and BMI are significant predictors of MHD and MLD, respectively. Although elderly and low-VC patients may have larger predictive variations, spirometry might be a substitute for LV-FB as a predictor of MHD.

Purpose: We aimed to evaluate the efficacy and safety of re-irradiation stereotactic body radiation therapy (SBRT) in patients with metastatic epidural spinal cord compression (MESCC) following high-dose conventional radiotherapy. Materials and methods: Twenty-one patients met the following eligibility criteria: with an irradiation history of 50 Gy₂ equivalent dose in 2-Gy fractions (EQD2) or more, diagnosed MESCC in the cervical or thoracic spines, and treated with re-irradiation SBRT of 24 Gy in 2 fractions between April 2018 and March 2023. Prior treatment was radiotherapy alone, not including surgery. The primary endpoint was a 1-year local failure rate. Overall survival (OS) and treatment-related adverse events were assessed as the secondary endpoints. Since our cohort includes one treatment-related death (TRD) of esophageal perforation, the cumulative esophageal dose was evaluated to find the dose constraints related to severe toxicities. Results: The median age was 68, and 14 males were included. The primary tumor sites (esophagus/lung/head and neck/others) were 6/6/7/2, and the median initial radiotherapy dose was 60 Gy₂ EQD2 (range: 50–105 Gy₂, 60–70/ > 70 Gy₂ were 11/4). Ten patients underwent surgery followed by SBRT and 11 SBRT alone. At the median follow-up time of 10.4 months, 17 patients died of systemic disease progression including one TRD. No radiation-induced myelopathy or nerve root injuries occurred. Local failure occurred in six patients, with a 1-year local failure rate of 29.3% and a 1-year OS of 55.0%. Other toxicities included five cases of vertebral compression fractures (23.8%) and one radiation pneumonitis. The cumulative esophageal dose was recommended as follows: D_max < 203, D_0.035 cc < 187, and D_1cc < 167 (Gy₃ in biological effective dose). Conclusion: Re-irradiation spine SBRT may be effective for selected patients with cervical or thoracic MESCC, even with high-dose irradiation histories. The cumulative dose assessment across the original and re-irradiated esophagus was recommended to decrease the risk of severe esophageal toxicities.

Purpose: This study evaluated the trends in the platform for stereotactic radiotherapy to the brain (SRT), utilizing the open data of the National Database published by the Ministry of Health, Labour, and Welfare. Materials and methods: This study analyzed data from FY2014 to FY2021. The practices included in the study were gamma knife surgery (GKS) and SRT with a linear accelerator (LINAC). The total number of outpatient and inpatient cases in each SRT system was evaluated annually. Results: From April 2014 to March 2022, the study included 212,016 cases (102,691 GKS and 109,325 LINAC) of the registered 1,996,540 radiotherapy cases. In the first year, 13,117 (54.1%) cases were GKS, and 11,128 (45.9%) were LINAC; after that, GKS decreased, and LINAC increased, reaching the same rate in FY2017. Compared to the first year, the final year showed 11,702 GKS (− 1415 or − 10.8%) and 17,169 LINAC (+ 6041 or + 54.3%), with an increase of 4626 total SRT cases to 28,871 (+ 19.1%). The percentage of outpatient treatment also increased from 4.6 to 11.8% for GKS and from 44.7 to 57.9% for LINAC. Conclusion: The study found a gradual decrease in the selection of GKS, an increasing trend in the selection of LINAC, and an increase in the overall number of stereotactic irradiations. In particular, the proportion of outpatient treatment increased, indicating that more than half of LINAC was selected for outpatient treatment.