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Author(s): Yukari Nagayasu [1]; Shoki Inui (corresponding author) [1]; Yoshihiro Ueda [1]; Akira Masaoka [1]; Masahide Tominaga [2]; Masayoshi Miyazaki [3]; Koji Konishi [1] INTRODUCTION Recently, high-precision radiation therapies, such [...], Aims: This study aimed to evaluate the geometrical accuracy of atlas-based auto-segmentation (ABAS), deformable image registration (DIR), and deep learning auto-segmentation (DLAS) in adaptive radiotherapy (ART) for head-and-neck cancer (HNC). Subjects and Methods: Seventeen patients who underwent replanning for ART were retrospectively studied, and delineated contours on their replanning computed tomography (CT2) images were delineated. For DIR, the planning CT image (CT1) of the evaluated patients was utilized. In contrast, ABAS was performed using an atlas dataset comprising 30 patients who were not part of the evaluated group. DLAS was trained with 143 patients from different patients from the evaluated patients. The ABAS model was improved, and a modified ABAS (mABAS) was created by adding the evaluated patients' own CT1 to the atlas datasets of ABAS (number of patients of the atlas dataset, 31). The geometrical accuracy of DIR, DLAS, ABAS, and mABAS was evaluated. Results: The Dice similarity coefficient in DIR was the highest, at >0.8 at all organs at risk. The mABAS was delineated slightly more accurately than the standard ABAS. There was no significant difference between ABAS and DLAS in delineation accuracy. DIR had the lowest Hausdorff distance (HD) value (within 10 mm). The HD values in ABAS, mABAS, and DLAS were within 16 mm. Conclusions: DIR delineation is the most geometrically accurate ART for HNC. Keywords: Adaptive radiotherapy, atlas-based auto-segmentation, automatic segmentation, deep learning auto-segmentation, deformable image registration, head and neck

Background and Aim: Effective treatment of lesions that develop in the irradiated area of head and neck squamous cell carcinoma is a major concern. This study aimed to clarify the efficacy and safety of endoscopic resection for such lesions. Methods: Among consecutive patients who underwent endoscopic resection for histologically proven head and neck squamous cell carcinoma between January 2014 and December 2021, those who received definitive radiotherapy/chemoradiotherapy before endoscopic resection were included in this single‐center, retrospective study. Short‐ and long‐term outcomes were evaluated. Results: Among 422 patients who underwent endoscopic resection for 615 lesions, 43 patients with 57 lesions were eligible. All 57 lesions were treated with endoscopic submucosal dissection and en bloc resection was achieved in all lesions. Grade 3 of Common Toxicity Criteria for Adverse Events v5.0 occurred in eight (19%) patients (dysphagia, seven; stricture, three; aspiration pneumonia, two; and pharyngeal necrosis, one [some cases overlapped]), but no grade ≥ 4 events occurred. Enteral nutrition by gastrostomy was temporarily required in two patients owing to dysphagia and laryngeal necrosis. During the median follow‐up of 40 (interquartile range, 29.5–61) months after endoscopic submucosal dissection for the lesions developed in the irradiated area, local recurrence and metachronous lesions developed in two (5%) and nine (21%) patients, respectively. However, total laryngectomies and tracheostomies were avoided in all patients. The 3‐year overall and disease‐specific survivals were 81% (95% confidence interval, 64%–91%) and 94% (95% confidence interval, 79%–99%), respectively. Conclusions: Favorable local control and safety of endoscopic submucosal dissection were demonstrated. [ABSTRACT FROM AUTHOR]

Brainstem metastases are challenging to manage owing to the critical neurological structures involved. Although stereotactic radiotherapy (SRT) offers targeted high doses while minimizing damage to adjacent normal tissues, the optimal dose fractionation remains undefined. This study evaluated the efficacy and safety of multifraction SRT with an inhomogeneous dose distribution. This retrospective study included 31 patients who underwent 33 treatments for 35 brainstem lesions using linear accelerator-based multifraction SRT (30 Gy in five fractions, 35 Gy in five fractions or 42 Gy in 10 fractions) with an inhomogeneous dose distribution (median isodose, 51.9%). The outcomes of interest were local failure, toxicity and symptomatic failure. The median follow-up time after brainstem SRT for a lesion was 18.6 months (interquartile range, 10.0–24.3 months; range, 1.8–39.0 months). Grade 2 toxicities were observed in two lesions, and local failure occurred in three lesions. No grade 3 or higher toxicities were observed. The 1-year local and symptomatic failure rates were 8.8 and 16.7%, respectively. Toxicity was observed in two of seven treatments with a gross tumor volume (GTV) greater than 1 cc, whereas no toxicity was observed in treatments with a GTV less than 1 cc. No clear association was observed between the biologically effective dose of the maximum brainstem dose and the occurrence of toxicity. Our findings indicate that multifraction SRT with an inhomogeneous dose distribution offers a favorable balance between local control and toxicity in brainstem metastases. Larger multicenter studies are needed to validate these results and determine the optimal dose fractionation. [ABSTRACT FROM AUTHOR]

Purpose: The study aimed to investigate the optimal isodose line (IDL) in linear accelerator‐based stereotactic radiotherapy for single brain metastasis, using HyperArc. We compared the dosimetric parameters for target and normal brain tissue among six plans with different IDLs. Methods: This study included 30 patients with single brain metastasis. We retrospectively generated six plans for each tumor with different IDLs (80%, 70%, 60%, 50%, 40%, and 33%) using HyperArc. All treatment plans were normalized to the prescription dose of 35 Gy in five fractions which was covered by 95% of the planning target volume (PTV), defined by adding a 1.0 mm margin to the gross tumor volume (GTV). The dosimetric parameters were compared among the six plans. Results: For GTV > 0.1 cm3, the ratio of brain–GTV volumes receiving 25 Gy to PTV (V25Gy/PTV) was significantly lower at IDL 40%–70% than at IDL 80% and 33% (p < 0.01, retrospectively). For GTV < 0.1 cm3, V25Gy/PTV decreased continuously as IDL decreased. The values of D99% and D80% for GTV increased with decreasing IDL. An IDL of 50% or less was required to achieve D99% of greater than 43 Gy and D80% of greater than 50 Gy. The mean values of D99% and D80% for IDL 50% were 44.3 and 51.9 Gy. Conclusion: The optimal IDL is 40%–50% for GTV > 0.1 cm3. These lower IDLs could increase D99% and D80% of GTV while lowering V25Gy of normal brain tissue, which may help reduce the risk of radiation necrosis and improve local control. [ABSTRACT FROM AUTHOR]

Objectives A portable respiratory training system with a gyroscope sensor (gyroscope respiratory training system [GRTS]) was developed and the feasibility of respiratory training was evaluated. Methods Simulated respiratory waveforms from a respiratory motion phantom and actual respirator waveforms from volunteers were acquired using the GRTS and Respiratory Gating for Scanners system (RGSC). Respiratory training was evaluated by comparing the stability and reproducibility of respiratory waveforms from patients undergoing expiratory breath-hold radiation therapy, with and without the GRTS. The stability and reproducibility of respiratory waveforms were assessed by root mean square error and gold marker placement-based success rate of expiratory breath-hold, respectively. Results The absolute mean difference for sinusoidal waveforms between the GRTS and RGSC was 2.0%. Among volunteers, the mean percentages of errors within ±15% of the respiratory waveforms acquired by the GRTS and RGSC were 96.1% for free breathing and 88.2% for expiratory breath-hold. The mean root mean square error and success rate of expiratory breath-hold (standard deviation) with and without the GRTS were 0.65 (0.24) and 0.88 (0.89) cm and 91.0% (6.9) and 89.1% (11.6), respectively. Conclusions Respiratory waveforms acquired by the GRTS exhibit good agreement with waveforms acquired by the RGSC. Respiratory training with the GRTS reduces inter-patient variability in respiratory waveforms, thereby improving the success of expiratory breath-hold radiation therapy. Advances in knowledge A respiratory training system with a gyroscope sensor is inexpensive and portable, making it ideal for respiratory training. This is the first report concerning clinical implementation of a respiratory training system. [ABSTRACT FROM AUTHOR]

Postoperative radiotherapy for breast cancer reportedly increases the risk of thoracic soft tissue sarcomas, particularly angiosarcomas; however, the risk in the Japanese population remains unknown. Therefore, this study aimed to investigate the incidence of thoracic soft tissue sarcoma among patients with breast cancer in Japan and determine its association with radiotherapy. This retrospective cohort study used data from the population-based cancer registry of the Osaka Prefecture. The inclusion criteria were female sex, age 20–84 years, diagnosis of breast cancer between 1990 and 2010, no supraclavicular lymph node or distant metastasis, underwent surgery and survived for at least 1 year. The primary outcome was the occurrence of thoracic soft tissue sarcomas 1 year or later after breast cancer diagnosis. Among the 13 762 patients who received radiotherapy, 15 developed thoracic soft tissue sarcomas (nine angiosarcomas and six other sarcomas), with a median time of 7.7 years (interquartile range, 4.0–8.6 years) after breast cancer diagnosis. Among the 27 658 patients who did not receive radiotherapy, four developed thoracic soft tissue sarcomas (three angiosarcomas and one other sarcoma), with a median time of 11.6 years after diagnosis. The 10-year cumulative incidence was higher in the radiotherapy cohort than in the non-radiotherapy cohort (0.087 vs. 0.0036%, P  < 0.001). Poisson regression analysis revealed that radiotherapy increased the risk of thoracic soft tissue sarcoma (relative risk, 6.8; 95% confidence interval, 2.4–24.4). Thus, although rare, breast cancer radiotherapy is associated with an increased risk of thoracic soft tissue sarcoma in the Japanese population. [ABSTRACT FROM AUTHOR]

Various locoregional treatments for localized hepatocellular carcinoma (HCC) have been developed. This retrospective study investigated the safety and feasibility of combining on-demand selective locoregional treatment for residual lesions after tumor shrinkage (complete response [CR] oriented) or for solitary or few drug-resistant lesions (progressive disease (PD) salvage) with first-line atezolizumab plus bevacizumab (atezo/bev) for unresectable HCC. Twenty-nine patients with unresectable HCC were included. Fourteen locoregional treatments were performed (CR oriented, 7; PD salvage, 7) in ten patients in the combination-therapy group. All patients in the combination-therapy group successfully achieved a CR or PD salvage status after the planned locoregional treatment. The objective response rate of the combination-therapy group (80.0%) was higher than that of the atezo/bev alone group (21.1%; p = 0.005). Progression-free survival (PFS) and overall survival (OS) were longer in the combination group (medians for PFS and OS not reached) than in the atezo/bev alone group (median PFS, 7.4 months; median OS, 19.8 months) (PFS, p = 0.004; OS, p < 0.001). The albumin–bilirubin score did not change, and no severe complications occurred after locoregional treatment. When performed in a minimally invasive manner, on-demand selective locoregional treatment combined with first-line atezo/bev could be safe and feasible for unresectable HCC. [ABSTRACT FROM AUTHOR]

To explore predictors of the histopathological response to preoperative chemoradiotherapy (CRT) in patients with pancreatic cancer (PC) using dual-energy computed tomography-reconstructed images. This retrospective study divided 40 patients who had undergone preoperative CRT (50–60 Gy in 25 fractions) followed by surgical resection into two groups: the response group (Grades II, III and IV, evaluated from surgical specimens) and the nonresponse group (Grades Ia and Ib). The computed tomography number [in Hounsfield units (HUs)] and iodine concentration (IC) were measured at the locations of the aorta, PC and pancreatic parenchyma (PP) in the contrast-enhanced 4D dual-energy computed tomography images. Logistic regression analysis was performed to identify predictors of histopathological response. Univariate analysis did not reveal a significant relation between any parameter and patient characteristics or dosimetric parameters of the treatment plan. The HU and IC values in PP and the differences in HU and IC between the PP and PC (ΔHU and ΔIC, respectively) were significant predictors for distinguishing the response (n  = 24) and nonresponse (n  = 16) groups (P  < 0.05). The IC in PP and ΔIC had a higher area under curve values [0.797 (95% confidence interval, 0.659–0.935) and 0.789 (0.650–0.928), respectively] than HU in PP and ΔHU [0.734 (0.580–0.889) and 0.721 (0.562–0.881), respectively]. The IC value could potentially be used for predicting the histopathological response in patients who have undergone preoperative CRT. [ABSTRACT FROM AUTHOR]

In volumetric modulated arc therapy (VMAT), the effect of an increase in skin surface dose due to topical agents might be negligible. We investigated the bolus effects of three types of topical agents in VMAT for head and neck cancer (HNC). Topical agents of different thicknesses (0.1, 0.5 and 2 mm) were prepared. When each topical agent was set, the surface doses were measured for the anterior static field and VMAT, with and without a thermoplastic mask. No significant differences were observed among the three topical agents. For topical agent thicknesses of 0.1, 0.5 and 2 mm, the increases in surface dose for the anterior static field without the thermoplastic mask were 7–9, 30–31 and 81–84%, respectively. With the thermoplastic mask, the corresponding increases were 5, 12–15 and 41–43%, respectively. The increases in surface dose for VMAT without the thermoplastic mask were 5–8, 16–19 and 36–39%, respectively, and those with the thermoplastic mask were 4, 7–10 and 15–19%, respectively. The rate of increase in surface dose with the thermoplastic mask was smaller than that without the thermoplastic mask. The increase in surface dose with topical agents of clinical standard thickness (0.02 mm) was estimated to be 2% with the thermoplastic mask. The increase in surface dose with topical agents in dosimetric simulation, compared with control situation, is not significant in clinical conditions for HNC patients. [ABSTRACT FROM AUTHOR]

Objective: Dosimetric potential of knowledge‐based RapidPlan planning model trained with HyperArc plans (Model‐HA) for brain metastases has not been reported. We developed a Model‐HA and compared its performance with that of clinical volumetric modulated arc therapy (VMAT) plans. Methods: From 67 clinical stereotactic radiosurgery (SRS) HyperArc plans for brain metastases, 47 plans were used to build and train a Model‐HA. The other 20 clinical HyperArc plans were recalculated in RapidPlan system with Model‐HA. The model performance was validated with the 20 plans by comparing dosimetric parameters for normal brain tissue between clinical plans and model‐generated plans. The 20 clinical conventional VMAT‐based SRS or stereotactic radiotherapy plans (CL‐VMAT) were reoptimized with Model‐HA (RP) and HyperArc system (HA), respectively. The dosimetric parameters were compared among three plans (CL‐VMAT vs. RP vs. HA) in terms of planning target volume (PTV), normal brain excluding PTVs (Brain − PTV), brainstem, chiasm, and both optic nerves. Results: In model validation, the optimization performance of Model‐HA was comparable to that of HyperArc system. In comparison to CL‐VMAT, there were no significant differences among three plans with respect to PTV coverage (p > 0.17) and maximum dose for brainstem, chiasm, and optic nerves (p > 0.40). RP provided significantly lower V20 Gy, V12 Gy, and V4 Gy for Brain − PTV than CL‐VMAT (p < 0.01). Conclusion: The Model‐HA has the potential to significantly reduce the normal brain dose of the original VMAT plans for brain metastases. [ABSTRACT FROM AUTHOR]