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Purpose We develop a deep learning (DL) radiomics model and integrate it with circulating tumor cell (CTC) counts as a clinically useful prognostic marker for predicting recurrence outcomes of early-stage non-small cell lung cancer (ES-NSCLC) patients treated with stereotactic body radiation therapy (SBRT). Methods and Materials A cohort of 421 NSCLC patients was used to train a DL model for gleaning informative imaging features from computed tomography (CT) data. The learned imaging features were optimized on a cohort of 98 ES-NSCLC patients treated with SBRT for predicting individual patient recurrence risks by building DL models on CT data and clinical measures. These DL models were validated on the third cohort of 60 ES-NSCLC patients treated with SBRT to predict recurrent risks and stratify patients into subgroups with distinct outcomes in conjunction with CTC counts. Results The DL model obtained a concordance-index of 0.880 (95% confidence interval: 0.879, 0.881). Patient subgroups with low and high DL risk scores had significantly different recurrence outcomes (p = 3.5e-04). The integration of DL risk scores and CTC measures identified 4 subgroups of patients with significantly different risks of recurrence (χ2= 20.11, p=1.6e-04). Patients with positive CTC measures post-SBRT were associated with increased risks of recurrence that were significantly different from patients with negative CTC measures (χ2= 4.03, p=0.0447). Conclusion In this first-ever study integrating DL radiomics models and CTC counts, our results suggested that this integration improves patient stratification compared with either imagining data or CTC measures alone in predicting recurrence outcomes for patients treated with SBRT for ES-NSCLC.

Purpose Despite the increasing use of stereotactic body radiation therapy for non–spine bone metastases (NSBM), there is no established standard for target delineation. The objective of this study was to provide consensus recommendations on clinical target volume (CTV) delineation based on international expert contours. Methods and Materials Eleven cases of NSBM were contoured by 9 international radiation oncologists. For each case, the gross tumor volume was provided on the simulation computed tomography scans with accompanying magnetic resonance imaging. Participants contoured the CTV and completed a clinical survey. Agreement between CTV contours were analyzed with simultaneous truth and performance level estimation using the kappa coefficient and the Dice similarity coefficient (DSC) and summarized to establish contouring recommendations. A direction-dependent analysis was applied to the consensus contours to quantify margins. Results All CTV contours were completed. Six participants used a single-dose level, whereas 3 used a 2-dose level simultaneous integrated boost (SIB) technique. For the SIB cases, the largest volume receiving a stereotactic body radiation therapy (SBRT) dose was used for contour analysis. There was substantial agreement between contours across cases with a mean kappa of 0.72 (mean sensitivity 0.85, mean specificity 0.97). The mean DSC value was 0.77 (range, 0.67-0.87). Consensus CTV contouring recommendations were (1) an intraosseous CTV margin of 5 to 10 mm should be strongly considered within contiguous bone; (2) an extraosseous margin of 5 to 10 mm should be strongly considered where there is soft tissue disease or cortical bone disruption; (3) CTVs should be manually cropped to respect anatomic barriers to spread (eg, peritoneal cavity, pleura, uninvolved joint space and cortical bone). Conclusions CTV contouring recommendations for NSBM-SBRT were established based on analysis of international expert consensus contours with a high level of agreement. These principles may provide guidance to treating physicians and inform future study until prospective clinical data can provide further refinement.

The Phoenix definition for biochemical failure (BCF) after radiotherapy uses nadir PSA (nPSA) + 2 ng/mL to classify a BCF and was derived from conventionally fractionated radiotherapy, which produces significantly higher nPSAs than stereotactic body radiotherapy (SBRT). We investigated whether an alternative nPSA-based threshold could be used to define post-SBRT BCFs.PSA kinetics data on 2038 patients from 9 institutions were retrospectively analyzed for low- and intermediate-risk PCa patients treated with SBRT without ADT. We evaluated the performance of various nPSA-based definitions. We also investigated the relationship of relative PSA decline (rPSA, PSAMedian follow-up was 71.9 months. BCF occurred in 6.9% of patients. Median nPSA was 0.16 ng/mL. False positivity of nPSA + 2 was 30.2%, compared to 40.9%, 57.8%, and 71.0% for nPSA + 1.5, nPSA + 1.0, and nPSA + 0.5, respectively. Among patients with BCF, the median lead time gained from an earlier nPSA + threshold definition over the Phoenix definition was minimal. Patients with BCF had significantly lower rates of early PSA decline (mean rPSA 1.19 vs. 0.39, p 0.0001) and were significantly more likely to reach nPSA + 2 ≥ 18 months (83.3% vs. 21.1%, p 0.0001). The proposed criterion (rPSA ≥ 2.6 or nPSA + 2 ≥ 18 months) had a sensitivity and specificity of 92.4% and 81.5%, respectively, for predicting BCF in patients meeting the Phoenix definition and decreased its false positivity to 6.4%.The Phoenix definition remains an excellent definition for BCF post-SBRT. Its high false positivity can be mitigated by applying additional criteria (rPSA ≥ 2.6 or time to nPSA + 2 ≥ 18 months).

EML4-ALK rearrangement is common in lung adenocarcinoma. The ALK inhibitors remarkably inhibit lung adenocarcinoma and reveal long-term beneficial effects in several patients. Advanced genetic testing technology reveals that EML4-ALK rearrangement has been observed in patients with lung squamous cell carcinoma. In the present study, we report a case of a 53-year-old patient with EML4-ALK rearranged in lung squamous carcinoma; PET/CT scan revealed brain and multiple bone metastases. First-line ALK-TKI combined with local stereotactic body radiation therapy indicated progression-free survival of 9 months. After progressive disease, treatment was switched to lorlatinib, with little efficacy and a total overall survival of 11 months. The emergence of drug resistance revealed that the genetic test result was EML4-ALK fusion (V3a/b variants), indicating a poor prognosis. In this study, we analyzed the treatment efficacy of ALK inhibitors and provided a research basis for the treatment of EML4-ALK rearranged in lung squamous cell carcinoma patients.

Background To evaluate the lung dose differences between three‐dimensional conformal radiotherapy (3D‐CRT) and intensity‐modulated radiation therapy (IMRT) techniques for lung stereotactic body radiation therapy (SBRT) and the correlations with tumor characteristics, such as size and location. Methods Dosimetric comparisons between the two SBRT techniques in high‐ and low‐ to intermediate‐dose regions were retrospectively performed using four planning indices and lung‐dose parameters in 31 lung tumors. The magnitude of differences in these parameters was analyzed with relation to the planning target volume (PTV) and location‐related parameters. Results The absolute differences between the two techniques in lung‐dose parameters were small in both ipsilateral and bilateral lungs. The dosimetric differences were mainly correlated with the PTV rather than location‐related parameters, with positive and negative correlations with the high‐dose and intermediate‐dose parameters, respectively. The distances from the ipsilateral lung centroid to the PTV center were not correlated with the differences in any of the lung‐dose parameters. Additionally, the negative correlations with the MLD and V20 differences disappeared after applying a more rapid dose fall‐off in the IMRT plans for tumors with small PTVs of ≤15 cc. Conclusions Lung dose differences between the 3D‐CRT and IMRT techniques for lung SBRT were mainly correlated with the PTV rather than location‐related parameters. Together with the dosimetric benefit in high‐dose lung regions of IMRT for larger tumors, the relative increases in the MLD and V20 for small‐sized tumors could be reduced by applying a more rapid dose fall‐off outside the PTV., The dosimetric differences between 3D‐CRT and IMRT were mainly correlated with the PTV rather than location‐related parameters, with positive and negative correlations with the high‐dose and intermediate‐dose parameters, respectively. Together with the dosimetric benefit in high‐dose lung regions of IMRT for larger tumors, the relative increases in the MLD and V20 for small‐sized tumors could be reduced by applying a more rapid dose fall‐off outside the PTV.

This paper aims to compare the dosimetric parameters of the original plan and the simulated plan to explore the clinical value of cone beam CT and planned CT image registration based on the target ...

BACKGROUND: Stereotactic body radiation therapy (SBRT) for liver cancer has shown promising therapeutic effects. Effective treatment relies not only on the precise delivery provided by image-guided radiation therapy (IGRT) but also high dose gradient formed around the treatment volume to spare functional liver tissue, which is highly dependent on the beam/arc angle selection. In this study, we aim to develop a decision support model to learn human planner’s beam navigation approach for beam angle/arc angle selection for liver SBRT. METHODS: A total of 27 liver SBRT/HIGRT patients (10 IMRT, 17 VMAT/DCA) were included in this study. A dosimetric budget index was defined for each beam angle/control point considering dose penetration through the patient body and liver tissue. Optimal beam angle setting (beam angles for IMRT and start/terminal angle for VMAT/DCA) was determined by minimizing the loss function defined as the sum of total dosimetric budget index and beam span penalty function. Leave-one-out validation was exercised on all 27 cases while weighting coefficients in the loss function was tuned in nested cross validation. To compare the efficacy of the model, a model plan was generated using automatically generated beam setting while retaining the original optimization constraints in the clinical plan. Model plan was normalized to the same planning target volume (PTV) V100% as the clinical plans. Dosimetric endpoints including PTV D98%, D2%, liver V20Gy and total MU were compared between two plan groups. Wilcoxon Signed-Rank test was performed with the null hypothesis being that no difference exists between two plan groups. RESULTS: Beam setting prediction was instantaneous. Mean PTV D98% was 91.3% and 91.3% (P=0.566), while mean PTV D2% was 107.9% and 108.1% (P=0.164) for clinical plan and model plan respectively. Liver V20Gy showed no significant difference (P=0.590) with 23.3% for clinical plan and 23.4% for the model plan. Total MU is comparable (P=0.256) between the clinical plan (avg. 2,389.6) and model plan (avg. 2,319.6). CONCLUSIONS: The evidence driven beam setting model yielded similar plan quality as hand-crafted clinical plan. It is capable of capturing human’s knowledge in beam selection decision making. This model could facilitate decision making for beam angle selection while eliminating lengthy trial-and-error process of adjusting beam setting during liver SBRT treatment planning.

PURPOSE To assess the added value of serial blood biomarkers in liver metastasis stereotactic body radiation therapy (SBRT). MATERIALS AND METHODS Eighty-nine patients were retrospectively included. Pre- and midtreatment blood samples were analyzed for potential biomarkers of the treatment response. Three biomarker classes were studied: gene mutation status, complete blood count, and inflammatory cytokine concentration in plasma. One-year local failure (LF) and 2-year overall survival (OS) were chosen as study end points. Multivariate logistic regression was used for response prediction. Added predictive benefit was assessed by quantifying the difference between the predictive performance of a baseline model (clinicopathologic and dosimetric predictors) and that of the biomarker-enhanced model, using three metrics: (1) likelihood ratio, (2) predictive variance, and (3) area under the receiver operating characteristic curve (AUC). RESULTS The most important predictors of LF were mutation in KRAS gene (hazard ratio [HR] = 2.92, 95% CI, [1.17 to 7.28], P = .02) and baseline and midtreatment concentration of plasma interleukin-6 (HR = 1.15 [1.04 to 1.26] and 1.06 [1.01 to 1.13], P = .01). Absolute lymphocyte count and platelet-to-lymphocyte ratio at baseline as well as neutrophil-to-lymphocyte ratio at baseline and before fraction 3 (HR = 1.33 [1.16 to 1.51] and 1.19 [1.09 to 1.30]) had the most significant association with OS ( P = .0003). Addition of baseline GEN and inflammatory plasma cytokine biomarkers in predicting LF, respectively, increased AUC by 0.06 (from 0.73 to 0.79) and 0.07 (from 0.77 to 0.84). In predicting OS, inclusion of midtreatment complete blood count biomarkers increased AUC from 0.72 to 0.80, along with significant boosts in likelihood ratio and predictive variance. CONCLUSION Inclusion of serial blood biomarkers leads to significant gain in predicting response to liver metastasis stereotactic body radiation therapy and can guide treatment personalization.

Stereotactic radiotherapy is an ever more common technique, regardless of the location treated. However, spinal stereotactic radiotherapy requires a particular technicality in order to ensure its proper realization. There is now a large literature defining the type of imaging to be used, the dose to be delivered and the delineation of target volumes. This technique can achieve a significant local control and an interesting analgesic efficiency. However, its place in relation to conventional radiotherapy remains limited because it requires MRI imaging and a significantly longer patient management during the treatment fraction. In this context, it is currently mainly restricted to oligometastatic patients or for re-irradiations.

Resume Objectif de l’etude La radiotherapie stereotaxique est realisee regulierement pour l’irradiation des metastases osseuses des os peripheriques mais sa place reste mal connue. Materiels et methodes Cette mise au point en radiotherapie stereotaxique des oligometastases osseuses des os peripheriques presente la synthese des donnees actuelles de la science relatives aux indications, a la simulation virtuelle, a la delineation des volumes cibles, a la dose totale et le fractionnement, a l’efficacite et la tolerance. Resultats Les cancers oligometastatiques sont classes ont 4 categories : oligorecidive, oligometastase, oligopersistance, oligoprogression. Le pronostic sera evalue selon les caracteristiques suivantes : tumeur primitive, caracteristiques quantitatives, cinetique, caracteristiques qualitatives. La delineation du volume tumoral macroscopique (GTV) comprend les extensions aux parties molles et a la moelle osseuse en s’aidant de l’IRM et de le TEP. Le volume cible anatomoclinique (CTV) correspond a une marge de 2 a 5 mm et le volume cible previsionnel (PTV) a une marge de 2 mm (a definir en fonction des contraintes de chaque service et contention). Les schemas d’irradiation les plus utilises sont : une seance unique de 18 a 24 Gy ; 24 Gy en deux fractions ; 27 a 30 Gy en trois fractions ; 30 a 35 Gy en cinq fractions. La radiotherapie stereotaxique permet un taux de controle local de 90 % a 1 an et un bon controle de la douleur. Les effets secondaires sont peu marques. Conclusion La radiotherapie stereotaxique est faisable, non-invasive, peu toxique et efficace avec un bon taux de controle local et un bon soulagement des douleurs. La principale problematique reste celle de la selection des patients les plus a meme d’en beneficier.

PURPOSE/OBJECTIVES: To estimate the effects of interfractional anatomic changes on dose to organs-at-risk (OARs) and tumors, as measured with cone-beam computed tomography (CBCT) image guidance for pancreatic stereotactic body radiotherapy (SBRT). MATERIALS/METHODS: We evaluated 11 patients with pancreatic cancer, whom were treated with SBRT (33–40 Gy in 5 fractions) using daily CT-on-rails (CTOR) image guidance immediately before treatment with breath-hold motion management. CBCT alignment was simulated in the treatment planning software by aligning the original planning CT to each fractional CTOR image set via fiducial markers. CTOR datasets were used to calculate fractional doses after alignment by applying the rigid shift of the planning CT and CTOR image sets to the planning treatment isocenter and recalculating the fractional dose. Accumulated dose to the gross tumor volume (GTV), tumor vessel interface (TVI), duodenum, small bowel, and stomach were calculated by summing the 5 fractional absolute dose-volume histograms (DVHs) into a single DVH for comparison with the original planned dose. RESULTS: Four patients had a GTV D100% of at least 1.5 Gy less than the fractional planned value in several fractions; 4 patients had fractional underestimation of duodenum dose by 1.0 Gy per fraction. The D1.0 cm(3)

Purpose To propose guidelines for lung stereotactic body radiation therapy (SBRT) when using Acuros XB (AXB) equivalent to the existing ones developed for convolution algorithms such as analytic anisotropic algorithm (AAA), considering the difference between the algorithms. Methods A retrospective analysis was performed on 30 lung patients previously treated with SBRT. The original AAA plans, which were developed using dynamic conformal arcs, were recalculated and then renormalized for planning target volume (PTV) coverage using AXB. The recalculated and renormalized plans were compared to the original plans based on V100% and V90% PTV coverage, as well as V105%, conformality index, D2cm , Rx/Dmax , R50, and Dmin . These metrics were analyzed nominally and on variations according to RTOG and NRG guidelines. Based on the relative difference between each metric in the AAA and AXB plans, new guidelines were developed. The relative differences in our cohort were compared to previously documented AAA to AXB comparisons found in the literature. Results AAA plans recalculated in AXB had a significant reduction in most dosimetric metrics. The most notable changes were in V100% (4%) and the conformality index (7.5%). To achieve equal PTV coverage, AXB required an average of 1.8% more monitor units (MU). This fits well with previously published data. Applying the new guidelines to the AXB plans significantly increased the number of minor violations with no change in major violations, making them comparable to those of the original AAA plans. Conclusion The relative difference found between AAA and AXB for SBRT lung plans has been shown to be consistent with previous works. Based on these findings, new guidelines for lung SBRT are recommended when planning with AXB.

PURPOSE Aim of this study is to assess the ability of contrast-enhanced CT image-based radiomic analysis to predict local response (LR) in a retrospective cohort of patients affected by pancreatic cancer and treated with stereotactic body radiation therapy (SBRT). Secondary aim is to evaluate progression free survival (PFS) and overall survival (OS) at long-term follow-up. METHODS Contrast-enhanced-CT images of 37 patients who underwent SBRT were analyzed. Two clinical variables (BED, CTV volume), 27 radiomic features were included. LR was used as the outcome variable to build the predictive model. The Kaplan-Meier method was used to evaluate PFS and OS. RESULTS Three variables were statistically correlated with the LR in the univariate analysis: Intensity Histogram (StdValue feature), Gray Level Cooccurrence Matrix (GLCM25_Correlation feature) and Neighbor Intensity Difference (NID25_Busyness feature). Multivariate model showed GLCM25_Correlation (P = 0.007) and NID25_Busyness (P = 0.03) as 2 independent predictive variables for LR. The odds ratio values of GLCM25_Correlation and NID25_Busyness were 0.07 (95%CI 0.01-0.49) and 8.10 (95%CI 1.20-54.40), respectively. The area under the curve for the multivariate logistic regressive model was 0.851 (95%CI 0.724-0.978). At a median follow-up of 30 months, median PFS was 7 months (95%CI 6-NA); median OS was 11 months (95%CI 10-22 months). CONCLUSIONS This analysis identified a radiomic signature that correlates with LR. To confirm these results, prospective studies could identify patient sub-groups with different rates of radiation dose-response to define a more personalized SBRT approach.

Vertebral compression fractures (VCF) are a common and severe complication of spine stereotactic body radiation therapy (SBRT). We sought to analyze how volumetric dosimetry and clinical factors were associated with the risk of VCF.We evaluated 173 spinal segments that underwent single fraction SBRT in 85 patients from a retrospective database. Vertebral bodies were contoured and dosimetric values were calculated. Competing risk models were used to evaluate the effect of clinical and dosimetry variables on the risk of VCF.Our primary endpoint was development of a post-SBRT VCF. New or progressive fractures were noted in 21/173 vertebrae (12.1%); the median time to fracture was 322 days. Median follow-up time was 426 days. Upon multivariable analysis, the percentages of vertebral body volume receiving20 Gy and24 Gy were significantly associated with increased risk of VCF (hazard ratio, 1.036, 1.104; P = .029, .044, respectively). No other patient or treatment factors were found to be significant on multivariable analysis. Sensitivity analysis revealed that the percentages of vertebral body volume receiving20 Gy and24 Gy required to obtain 90% sensitivity for predicting vertebral body fracture were 24% and 0%, respectively.VCF is a common complication after SBRT, with a crude incidence of 12.1%. Treatment plans that permit higher volumes receiving doses20 Gy and24 Gy to the vertebral body are associated with increased risk of VCF. To achieve 90% sensitivity for predicting VCF post-SBRT, the percentage of vertebral volume receiving20 Gy should be24% and maximum point dose should be24 Gy. These results may help guide clinicians when evaluating spine SBRT treatment plans to minimize the risk of developing posttreatment VCF.

BACKGROUND: Thymomas can benefit of cytoreductive surgery even if a complete resection is not feasible. The pleural cavity is the most common site of progression and the resection of pleural metastases can be performed in selected patients. We evaluated the results of stereotactic body radiation therapy for the treatment of pleural metastases in patients not eligible for surgery. METHODS: We retrospectively selected 22 patients treated with stereotactic body radiation therapy for pleural metastases between 2013 and 2019. According to RECIST criteria 1.1 modified for thymic epithelial tumors, time to local failure and progression free survival were calculated using Kaplan-Meier method. RESULTS: The median age was 40 years (range, 29–73 years). There were 1 A, 3 AB, 3 B1, 3 B2, 3 B2/B3 and 9 B3 thymomas. Pleural metastases and primary tumor were synchronous in 8 patients. Five patients had a single pleural metastatic site and 17 presented multiple localizations. Sixteen patients received stereotactic body radiation therapy on multiple sites of pleural metastases. The median dose of radiation was 30 Gy (range, 24–40 Gy). With a median follow-up of 33.2 months (95% CI: 13.1–53.3 months), ten patients experienced disease progression with a median progression free survival was 20.4 months (95% CI: 10.7–30.0 months). The disease control rate was 79% and 41% after 1 and 2 years, respectively. Local disease control rate was 92% and 78% after 1 and 2 years, respectively. There were not significant differences in progression free survival between patients diagnosed with synchronous and metachronous metastases (P=0.477), across those treated or not with chemotherapy (P=0.189) and between those who received or not a previous surgical resection of the pleural metastases (P=0.871). There were not grade 3–4 toxicities related to the treatment. CONCLUSIONS: Stereotactic body radiation therapy of pleural metastases is feasible and offers a promising local control of diseases. The impact of this treatment on patients’ survival is hardly predictable because of the heterogeneous clinical behavior of thymomas.

This study aimed to quantitatively clarify the baseline drift for each respiratory cycle in two respiratory-gating methods using the intra-beam respiratory motion data of lung cancer patients. The residual motion and dose distribution were calculated based on intra-beam respiratory motion data with the baseline drift. To quantify the baseline drift \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}$\Delta$\end{document} during irradiation, it was defined as the inclination between the detected expiration point and the expiration point in the next cycle in the anterior–posterior (AP), cranial–caudal (CC) and left–right (LR) directions obtained using an in-house programme. The baseline drift value reached up to 0.74 mm/s in the CC direction as per the respiratory motion data of 10 patients. The homogeneity index (HI) of the phase-gating method tended to increase because the target was irradiated even when the amplitude position of the target differed from period to period. In contrast, the amplitude-gating method enabled irradiation considering the amplitude position of the target because the gating window was set considering the amplitude position of the respiratory motion. The respiratory-gating methods and respiratory phase in respiratory-gating lung stereotactic body radiation therapy (SBRT) must be determined based on the respiratory motion of the patients.

Stereotactic body radiation therapy (SBRT) is an established limb-sparing treatment for dogs with appendicular osteosarcoma (OSA) and pathologic fractures are a common sequela. The objectives of this retrospective, observational, and descriptive study were to develop and evaluate objective CT criteria for predicting pathologic fractures and assess impacts on survival time. Included dogs had confirmed or suspected appendicular OSA, available CT scans, available outcome data, and were treated with SBRT. For each study, the number of quartiles affected by lysis on the most severely affected transverse slice, longest measurable length of contiguous full cortical lysis, presence of subchondral bone lysis, and ratio of the length of the affected bone to normal bone were recorded. A scoring system was developed for assigning grades (summed score 1-4 = grade 1, 5-7 = grade 2, and 8 or greater = grade 3.) A total of 127 CT datasets were sampled (123 patients). The median summed score was 7. The grade was correlated with pathologic fracture development (23% of grade 1, 35% of grade 2, and 57% of grade 3 resulting in fracture, P = 0.028). Subchondral bone lysis was correlated with fracture (odds ratio, 2.2, P = 0.02). Percent affected bone ≥40% was associated with decreased survival (P = 0.002). Dogs with

The use of stereotactic body radiation therapy (SBRT) to treat non-spine bone metastases (NSBM) is becoming increasingly common in clinical practice. The clinical advantages of SBRT include good pain control and high local control rates, although only limited data are available. The Spanish Society of Radiation Oncology (SEOR) SBRT group recently convened a task force of experts in the field to address key questions related to SBRT for NSBM, including treatment indications, planning, techniques, and dose fractionation. The task force reviewed the available literature to develop evidence-based recommendations for the safe application of NSBM SBRT and to standardize and optimize SBRT processes. The present document provides a comprehensive analysis of the available data, including ongoing clinical trials and controversies, providing clinically applicable recommendations.

Despite advances in drug and catheter ablation therapy, long-term recurrence rates for ventricular tachycardia remain suboptimal. Cardiac stereotactic body radiotherapy (SBRT) is a novel treatment that has demonstrated reduction of arrhythmia episodes and favorable short-term safety profile in treatment-refractory patients. Nevertheless, the current clinical experience is early and limited. Recent studies have highlighted variable duration of treatment effect and substantial recurrence rates several months postradiation. Contributing to these differential outcomes are disparate approaches groups have taken in planning and delivering radiation, owing to both technical and knowledge gaps limiting optimization and standardization of cardiac SBRT.In this report, we review the historical basis for cardiac SBRT and existing clinical data. We then elucidate the current technical gaps in cardiac radioablation, incorporating the current clinical experience, and summarize the ongoing and needed efforts to resolve them.Cardiac SBRT is an emerging therapy that holds promise for the treatment of ventricular tachycardia. Technical gaps remain, to be addressed by ongoing research and growing clincial experience.

Microwave (MW) ablation and stereotactic body radiation therapy (SBRT) have potentially complementary advantages and limitations for treating inoperable renal cell carcinoma (RCC). Combining SBRT and MWA may optimize tumor control and toxicity for patients with larger (>5 cm) RCCs or those with vascular involvement. We retrospectively reviewed patients at our institution with RCC treated between 2014 – 2018 to identify patients treated with a combination of SBRT and MW ablation. Seven patients with RCC were treated with combination of SBRT and MW ablation, median tumor size of 6.4 cm. Local control was 100% with a median follow-up of 15 months. Four patients experienced grade 2 nausea during SBRT. Three patients experienced toxicities after MW ablation, two with grade 1 hematuria and one with grade 3 retroperitoneal bleed/collecting system injury. Median eGFR preceding and following SBRT and MW ablation was 69 mL/min/1.73m2 and 68 mL/min/1.73m2 (p=0.19) respectively. In patients who are not surgical candidates, larger RCCs or those with vascular invasion are challenging to treat. Combination treatment with SBRT and MW ablation may balance the risks and benefits of both therapies and demonstrates high local control in our series. MW ablation and SBRT have potentially complementary advantages and limitations.

Purpose: To investigate the safety and efficacy of hypofractionated radiation therapy (HFRT) in patients with non-small cell lung cancer who are unfit for surgery or stereotactic body radiation therapy (SBRT) at our institution.Materials and Methods: From May 2007 to December 2018, HFRT was used to treat 68 lesions in 64 patients who were unsuitable for SBRT because of central tumor location, large tumor size, or contiguity with the chest wall. The HFRT schedule included a dose of 50–70 Gy delivered in 10 fractions over 2 weeks. The primary outcome was freedom from local progression (FFLP), and the secondary endpoints included overall survival (OS), disease-free survival, and toxicities.Results: The median follow-up period was 25.5 months (range, 5.3 to 119.9 months). The FFLP rates were 79.8% and 67.8% at 1 and 2 years, respectively. The OS rates were 82.8% and 64.1% at 1 and 2 years, respectively. A larger planning target volume was associated with lower FFLP (p = 0.023). Dose escalation was not associated with FFLP (p = 0.964). Four patients (6.3%) experienced grade 3–5 pulmonary toxicities. Tumor location, central or peripheral, was not associated with either grade 3 or higher toxicity.Conclusion: HFRT with 50–70 Gy in 10 fractions demonstrated acceptable toxicity; however, the local control rate can be improved compared with the results of SBRT. More studies are required in patients who are unfit for SBRT to investigate the optimal fractionation scheme.

The purpose of this study was to assess prospectively the efficacy and safety of stereotactic body radiation therapy (SBRT) for adrenal gland metastasis, with a focus on the assessment of the irradiated subjects’ endocrinological function. A total of 36 patients were enrolled from 2017 to 2020 in this prospective phase II trial. Patients were treated with Linac-based SBRT, with a dose of 45 Gy in 3 consecutive fractions. Primary end-point was local control (LC) of the treated lesions and secondary end-points included evaluation of acute and late toxicity, progression free survival (PFS), overall survival (OS) and the impact on the hormonal production of adrenal glands. With a median follow-up of 9.5 months, LC rates at 1 and 2 years were 94.7% and 88.4%, respectively. Rates of PFS at 1 and 2 years were 50.5% and 29.8%, with a median PFS of 14.7 months. Rates of OS at 1 and 2 years were 62.9% and 44.1%. At univariate analysis, oligorecurrence was associated with better OS compared to oligoprogressive or synchronous metastatic disease. No grade 3 or greater toxicities were registered and only a minority of patients (22.2%) reported mild treatment-related side effects. Hormonal and electrolytes production was assessed before and after treatment, showing only a slight and transient variation within the reference ranges. SBRT on adrenal metastases has been confirmed to be a feasible and effective treatment. With an excellent disease control and the preservation of the endocrine function, SBRT with ablative dose can be considered a viable alternative to more invasive approaches.

Objective To evaluate the efficacy and safety of SBRT for localized prostate cancer (PCa) with CyberKnife in China. Moreover, it is the largest-to-date pilot study to report 5-year outcomes of SBRT for localized PCa from China. Methods In this retrospective study, 133 PCa patients in our center were treated by SBRT with CyberKnife (Accuray Inc., Sunnyvale, USA) from October 2012 to July 2019. Follow-up was performed every 3 months for efficacy and toxicity evaluation. Biochemical progression-free survival (bPFS) and toxicities were assessed using the Phoenix definition and the Common Terminology Criteria for Adverse Events (CTCAE) v.5.0, respectively. Factors predictive of bPFS were identified with COX regression analysis. Results 133 patients (10 low-, 21 favorable intermediate-, 31 unfavorable intermediate-, 45 high-, and 26 very high risk cases on the basis of NCCN risk classification) with a median age of 76 years (range 54–87 years) received SBRT. The median dose was 36.25 Gy (range 34–37.5 Gy) in 5 fractions. Median follow-up time was 57.7 months (3.5–97.2 months). The overall 5-year bPFS rate was 83.6% for all patients. The 5-year bPFS rate of patients with low-, favorable intermediate-, unfavorable intermediate-, high-, and very high risk PCa was 87.5%, 95.2%, 90.5%, 86.3%, and 61.6%, respectively. Urinary symptoms were all alleviated after SBRT. All patients tolerated SBRT with 1 (0.8%) patient reporting grade-3 acute and 1 (0.8%) patient reporting grade-3 late genitourinary (GU) toxicity, respectively. There were no grade 4 toxicities. Gleason score (P Conclusion SBRT is an efficient and safe treatment modality for localized PCa with high 5-year bPFS rates and acceptable toxicities.

Purpose To demonstrate fast treatment planning feasibility of stereotactic body radiation therapy (SBRT) for centrally located lung tumors on Halcyon Linac via a previously validated knowledge‐based planning (KBP) model to support offline adaptive radiotherapy. Materials/methods Twenty previously treated non‐coplanar volumetric‐modulated arc therapy (VMAT) lung SBRT plans (c‐Truebeam) on SBRT‐dedicated C‐arm Truebeam Linac were selected. Patients received 50 Gy in five fractions. c‐Truebeam plans were re‐optimized for Halcyon manually (m‐Halcyon) and with KBP model (k‐Halcyon). Both m‐Halcyon and k‐Halcyon plans were normalized for identical or better target coverage than clinical c‐Truebeam plans and compared for target conformity, dose heterogeneity, dose fall‐off, and dose tolerances to the organs‐at‐risk (OAR). Treatment delivery parameters and planning times were evaluated. Results k‐Halcyon plans were dosimetrically similar or better than m‐Halcyon and c‐Truebeam plans. k‐Halcyon and m‐Halcyon plan comparisons are presented with respect to c‐Truebeam. Differences in conformity index were statistically insignificant in k‐Halcyon and on average 0.02 higher (p = 0.04) in m‐Halcyon plans. Gradient index was on average 0.43 (p = 0.006) lower and 0.27 (p = 0.02) higher for k‐Halcyon and m‐Halcyon, respectively. Maximal dose 2 cm away in any direction from target was statistically insignificant. k‐Halcyon increased maximal target dose on average by 2.9 Gy (p

Purpose Cardiac radioablation using stereotactic body radiation therapy is gaining popularity as a noninvasive treatment for otherwise refractory ventricular arrhythmias. As radiation oncologists might be unaccustomed to the lexicon used by cardiologists to describe the location of arrhythmogenic foci, a preliminary guide to cardiac-specific anatomy and orientation is needed to foster effective communication between the radiation oncologist and cardiology team. Methods and Materials Electrocardiogram-gated and respiratory-gated computed tomography imaging was acquired per institutional protocol. Additional relevant imaging modalities are described. The American Heart Association 17-segment model is described in detail because this framework is used frequently by cardiologists to describe the location left ventricular abnormalities. Results A step-by-step guide is provided for properly rotating the heart from standard orthogonal views obtained during radiation simulation to the cardiac-specific orientation needed to appreciate the 17-segment model. Once the proper configuration is achieved, the location of each segment is defined in detail. Conclusions This atlas serves as an introduction to the relevant anatomy and principles, and it provides a suggested approach to help delineate cardiac radioablation targets using the established American Heart Association 17-segment model.

OBJECTIVE In the treatment of spinal metastases with stereotactic body radiation therapy (SBRT), vertebral compression fracture (VCF) is a common and potentially morbid complication. Better methods to identify patients at high risk of radiation-induced VCF are needed to evaluate prophylactic measures. Radiomic features from pretreatment imaging may be employed to more accurately predict VCF. The objective of this study was to develop and evaluate a machine learning model based on clinical characteristics and radiomic features from pretreatment imaging to predict the risk of VCF after SBRT for spinal metastases. METHODS Vertebral levels C2 through L5 containing metastases treated with SBRT were included if they were naive to prior surgery or radiation therapy, target delineation was based on consensus guidelines, and 1-year follow-up data were available. Clinical features, including characteristics of the patient, disease, and treatment, were obtained from chart review. Radiomic features were extracted from the planning target volume (PTV) on pretreatment CT and T1-weighted MRI. Clinical and radiomic features selected by least absolute shrinkage and selection operator (LASSO) regression were included in random forest classification models, which were trained to predict VCF within 1 year after SBRT. Model performance was assessed with leave-one-out cross-validation. RESULTS Within 1 year after SBRT, 15 of 95 vertebral levels included in the analysis demonstrated new or progressive VCF. Selected clinical features included BMI, performance status, total prescription dose, dose to 99% of the PTV, lumbar location, and 2 components of the Spine Instability Neoplastic Score (SINS): lytic tumor character and spinal misalignment. Selected radiomic features included 5 features from CT and 3 features from MRI. The best-performing classification model, derived from a combination of selected clinical and radiomic features, demonstrated a sensitivity of 0.844, specificity of 0.800, and area under the receiver operating characteristic (ROC) curve (AUC) of 0.878. This model was significantly more accurate than alternative models derived from only selected clinical features (AUC = 0.795, p = 0.048) or only components of the SINS (AUC = 0.579, p < 0.0001). CONCLUSIONS In the treatment of spinal metastases with SBRT, a machine learning model incorporating both clinical features and radiomic features from pretreatment imaging predicted VCF at 1 year after SBRT with excellent sensitivity and specificity, outperforming models developed from clinical features or components of the SINS alone. If validated, these findings may allow more judicious selection of patients for prophylactic interventions.

Eine Strahlentherapie kleiner Zielvolumina mit sehr hohen Einzeldosen auf 1 bis ca. 12 Fraktionen verteilt – unter Bildfuhrung und in tumorabladierender Absicht durchgefuhrt – wird bei extrakraniellen Tumoren oder Metastasen als extrakranielle Stereotaxie („stereotactic body radiation therapy“ [SBRT]) bezeichnet. Strahlenbiologisch werden neben der Schadigung der DNA der Tumorzellen auch die Tumorgefase okkludiert und immunologische Effekte ausgelost. Die sichere Durchfuhrung der SBRT bedeutet einen sehr hohen physikalisch-technischen Aufwand, um eine ausreichende Schonung der gesunden Organe gewahrleisten zu konnen. Klinisch bietet die SBRT weite Einsatzmoglichkeiten in der kurativen Therapie (z. B. beim nichtkleinzelligen Bronchialkarzinom im Stadium I). Zudem ist sie eine konservative, effektive und gut vertragliche Option zur Behandlung einzelner Metastasen und ein optimaler Kombinationspartner in der Therapie oligometastasierter Tumorstadien.

BACKGROUND: There are no established threshold values regarding the degree of growth on imaging when assessing response of spinal metastases treated with stereotactic body radiation therapy (SBRT). OBJECTIVE: To determine a magnetic resonance imaging-based minimum detectable difference (MDD) in gross tumor volume (GTV) and its association with 1-yr radiation site-specific (RSS) progression-free survival (PFS). METHODS: GTVs at baseline and first 2 post-SBRT scans (Post1 and Post2, respectively) for 142 spinal segments were contoured, and percentage volume change between scans calculated. One-year RSS PFS was acquired from medical records. The MDD was determined. The MDD was compared against optimal thresholds of GTV changes associated with 1-yr RSS PFS using Youden's J index, and receiver operating characteristic curves between timepoints compared to determine which timeframe had the best association. RESULTS: A total of 17 of the 142 segments demonstrated progression. The MDD was 10.9%. Baseline-Post2 demonstrated the best performance (area under the curve [AUC] 0.90). Only Baseline-Post2 had an optimal threshold > MDD at 14.7%. Due to large distribution of GTVs, volumes were split into tertiles. Small tumors (GTV 8.3 cc) had 2 timepoints where optimal thresholds > MDD: Baseline-Post2 (13.3%; AUC 0.97) and Post1-Post2 (11.8%; AUC 0.66). Baseline-Post2 had the best association with RSS PFS for all tertiles. CONCLUSION: Given a MDD of 10.9%, for small GTVs, larger (>37%) changes were required before local failure could be determined, compared to 11% to 13% for medium/large tumors.

Introduction Dose-response relationships for local control of lung tumours treated with stereotactic body radiotherapy (SBRT) have proved ambiguous, however, these have been based on the prescribed or planned dose. Delivered dose to the target may be a better predictor for local control. In this study, the probability of the delivered minimum dose to the clinical target volume (CTV) in relation to the prescribed dose was estimated for a cohort of patients, considering geometrical uncertainties. Materials and methods Delivered doses were retrospectively simulated for 50 patients treated with SBRT for lung tumours, comparing two image-guidance techniques: pre-treatment verification computed tomography (IG1) and online cone-beam computed tomography (IG2). The prescribed dose was typically to the 67% isodose line of the treatment plan. Simulations used in-house software that shifted the static planned dose according to a breathing motion and sampled setup/matching errors. Each treatment was repeatedly simulated, generating a multiplicity of dose-volume histograms (DVH). From these, tumour-specific and population-averaged statistics were derived. Results For IG1, the probability that the minimum CTV dose (D98%) exceeded 100% of the prescribed dose was 90%. With IG2, this probability increased to 99%. Conclusions Doses below the prescribed dose were delivered to a considerably larger part of the population prior to the introduction of online soft-tissue image-guidance. However, there is no clear evidence that this impacts local control, when compared to previous published data.

Background To report on our institutional experience using Proton stereotactic body radiation therapy (SBRT) for patients with liver metastases. Methods All patients with liver metastases treated with Proton SBRT between September 2012 and December 2017 were retrospectively analyzed. Local control (LC) and overall survival (OS) were estimated using the Kaplan-Meier method calculated from the time of completion of Proton SBRT. LC was defined according to Response Evaluation Criteria in Solid Tumors (RECIST) guidelines (version 1.1). Toxicity was graded according to Common Terminology Criteria for Adverse Events (CTCAE) version 4.0. Results Forty-six patients with 81 lesions were treated with Proton SBRT. The median age was 65.5 years old (range, 33-86 years) and the median follow up was 15 months (range, 1-54 months). The median size of the gross tumor volume (GTV) was 2.5 cm (range, 0.7-8.9 cm). Two or more lesions were treated in 56.5% of patients, with one patient receiving treatment to a total of five lesions. There were 37 lesions treated with a biologically effective dose (BED) ≤60, 9 lesions with a BED of 61-80, 22 lesions with a BED of 81-100, and 13 lesions with a BED >100. The 1-year and 2-year LC for all lesions was 92.5% (95% CI, 82.7% to 96.8%). The grade 1 and grade 2 toxicity rates were 37% and 6.5%, respectively. There were no grade 3 or higher toxicities and no cases of radiation-induced liver disease (RILD). Conclusions Proton SBRT for the treatment of liver metastases has promising LC rates with the ability to safely treat multiple liver metastases. Accrual continues for our phase II trial treating liver metastases with Proton SBRT to 60 GyE (Gray equivalent) in 3 fractions.

Background To compare the clinical outcomes of stereotactic body radiation therapy (SBRT) and fractionated radiation therapy (FRT) for primary liver cancer with portal vein tumor thrombus (PVTT). Methods This retrospective study included 36 patients who underwent SBRT and 36 patients who underwent FRT from August 2016 to June 2018. Patients were evaluated for short-term efficacy, long-term efficacy, AEs, and quality of life before and after treatment. Results With a median follow-up of 28.8 months (26–36 months), 27 patients survived in the SBRT group while 19 patients survived in the FRT group. The survival rate in the SBRT group was statistically higher than that of the FRT group after 6 months (80.56% vs. 58.33%; P = 0.041), 12 months (77.78% vs. 55.56%; P = 0.046) and 24 months 75.00% vs. 52.78%; P = 0.049). The median whole survival time of the SBRT group was 13.3 months (95% CI 12.83–13.97), which was statistically longer than 9.8 months in the FRT group (95% CI 8.83–10.97, P Conclusion SBRT had better clinical outcomes than FRT for primary liver cancer with PVTT.

Background and purpose When treating lung tumors with stereotactic body radiation therapy (SBRT), patient immobilization is of outmost importance. In this study, the intra‐fractional shifts of the patient (based on bony anatomy) and the tumor (based on the visible target volume) are quantified, and the associated impact on the delivered dose is estimated for a frameless immobilization approach in combination with surface guided radiation therapy (SGRT) monitoring. Methods Cone beam computed tomographies (CBCT) were collected in free breathing prior and after each treatment for 25 patients with lung tumors, in total 137 fractions. The CBCT collected after each treatment was registered to the CBCT collected before each treatment with focus on bony anatomy to determine the shift of the patient, and with focus on the visible target volume to determine the shift of the tumor. Rigid registrations with 6 degrees of freedom were used. The patients were positioned in frameless immobilizations with their position and respiration continuously monitored by a commercial SGRT system. The patients were breathing freely within a preset gating window during treatment delivery. The beam was automatically interrupted if isocenter shifts >4 mm or breathing amplitudes outside the gating window were detected by the SGRT system. The time between the acquisition of the CBCTs was registered for each fraction to examine correlations between treatment time and patient shift. The impact of the observed shifts on the dose to organs at risk (OAR) and the gross tumor volume (GTV) was assessed. Results The shift of the patient in the CBCTs was ≤2 mm for 132/137 fractions in the vertical (vrt) and lateral (lat) directions, and 134/137 fractions in the longitudinal (lng) direction and ≤4 mm in 134/137 (vrt) and 137/137 (lat, lng) of the fractions. The shift of the tumor was ≤2 mm in 116/137 (vrt), 123/137 (lat) and 115/137 (lng) fractions and ≤4 mm in 136/137 (vrt), 137/137 (lat), and 135/137 (lng) fractions. The maximal observed shift in the evaluated CBCT data was 4.6 mm for the patient and 7.2 mm for the tumor. Rotations were ≤3.3ᵒ for all fractions and the mean/standard deviation were 0.2/1.0ᵒ (roll), 0.1/0.8ᵒ (yaw), and 0.3/1.0ᵒ (pitch). The SGRT system interrupted the beam due to intra‐fractional isocenter shifts >4 mm for 21% of the fractions, but the patients always returned within tolerance without the need of repositioning. The maximal observed isocenter shift by the SGRT system during the beam holds was 8 mm. For the respiration monitoring, the beam was interrupted at least one time for 54% of the fractions. The visual tumor was within the planned internal target volume (ITV) for 136/137 fractions in the evaluated CBCT data collected at the end of each fraction. For the fraction where the tumor was outside the ITV, the D98% for the GTV decreased with 0.4 Gy. For the OARs, the difference between planned and estimated dose from the CBCT data (D2% or Dmean) was ≤2.6% of the prescribed PTV dose. No correlation was found between treatment time and the magnitude of the patient shift. Conclusions Using SGRT for motion management and respiration monitoring in combination with a frameless immobilization is a feasible approach for lung SBRT.

Objective To evaluate the influence of target dose heterogeneity on normal tissue dose sparing for peripheral lung tumor stereotactic body radiation therapy (SBRT). Methods Based on the volumetric-modulated arc therapy (VMAT) technique, three SBRT plans with homogeneous, moderate heterogeneous, and heterogeneous (HO, MHE, and HE) target doses were compared in 30 peripheral lung tumor patients. The prescription dose was 48 Gy in 4 fractions. Ten rings outside the PTV were created to limit normal tissue dosage and evaluate dose falloff. Results When MHE and HE plans were compared to HO plans, the conformity index of the PTV was increased by approximately 0.08. The median mean lung dose (MLD), V5, V10, V20 of whole lung, D2%, D1cc, D2cc of the rib, V30 of the rib, D2% and the maximum dose (Dmax) of the skin, and D2% and Dmax of most mediastinal organs at risk (OARs) and spinal cord were reduced by up to 4.51 Gy or 2.8%. Analogously, the median Dmax, D2% and mean dose of rings were reduced by 0.71 to 8.46 Gy; and the median R50% and D2cm were reduced by 2.1 to 2.3 and 7.4% to 8.0%, respectively. Between MHE and HE plans there was little to no difference in OARs dose and dose falloff beyond the target. Furthermore, the dose sparing of rib V30 and the mean dose of rings were negatively correlated with the rib and rings distance from tumor, respectively. Conclusions For peripheral lung tumor SBRT, target conformity, normal tissue dose, and dose falloff around the target could be improved by loosening or abandoning homogeneity. While there was negligible further dose benefit for the maximum target dose above 125% of the prescription, dose sparing of normal tissue derived from a heterogeneous target decreased as the distance from the tumor increased.

Aim:Induction chemotherapy (iC) followed by concurrent chemoradiation has been shown to improve overall survival (OS) for locally advanced pancreatic cancer (LAPC). However, the survival benefit of stereotactic body radiation therapy (SBRT) versus conventionally fractionated radiation therapy (CFRT) following iC remains unclear.Materials and methods:The National Cancer Database (NCDB) was queried for primary stage III, cT4N0-1M0 LAPC (2004–15). Kaplan–Meier analysis, Cox proportional hazards method and propensity score matching were used.Results:Among 872 patients, 738 patients underwent CFRT and 134 patients received SBRT. Median follow-up was 24·3 and 22·9 months for the CFRT and SBRT cohorts, respectively. The use of SBRT showed improved survival in both the multivariate analysis (hazards ratio 0·78, p = 0·025) and 120 propensity-matched pairs (median OS 18·1 versus 15·9 months, p = 0·004) compared to the CFRT.Findings:This NCDB analysis suggests survival benefit with the use of SBRT versus CFRT following iC for the LAPC.

PURPOSE: This study aims to evaluate the planned dose of stereotactic body radiation therapy (SBRT) for treating early peripheral non-small cell lung cancer (NSCLC) using the non-coplanar radiation from Cyberknife and Varian linac. Moreover, this study investigates whether Cyberknife and Varian linac are qualified for non-coplanar radiation SBRT for treating early peripheral NSCLC, and which one is better for protecting organs at risk (OARs). METHODS: Retrospective analysis was performed based on the Cyberknife radiation treatment plans (RTPs) and Varian Eclipse RTPs of 10 patients diagnosed with early peripheral NSCLC. The dose distributions in the target and OARs were compared between the RTPs of Cyberknife and Varian Eclipse using Mim medical imaging software. RESULTS: For PTV, no significant difference in D98 and D95 between the Cyberknife and Eclipse was observed (t = –0.35, –1.67, P > 0.05). The homogeneity indexes (HIs) of Cyberknife plans are higher (t = 71.86, P 0.05) than Varian Eclipse plans. CONCLUSION: To fulfill SBRT by non-coplanar radiation, Cyberknife is recommended for the institutions equipped with Cyberknife, while Varian linac can be applied for the institutions that have not adopted Cyberknife in clinical radiotherapy yet.

Purpose Stereotactic body radiotherapy (SBRT) delivers ablative doses with excellent local control. However, implementing SBRT for abdominal and pelvic tumors has been limited by the risk for treatment‐related gastrointestinal toxicity. MRI‐guided radiotherapy may ameliorate these risks and increase the therapeutic ratio. We report the clinical outcomes of stereotactic MRI‐guided adaptive radiotherapy (SMART) for primary and metastatic tumors in the abdomen and pelvis. Methods From November 2014 to August 2017, the first 106 consecutive patients with 121 tumors in the abdomen and pelvis were treated with SMART at a single institution. Of the cohort, 41.5%, 15.1%, and 43.4% had primary, locally recurrent, and oligometastatic tumors, respectively. SMART was delivered using a tri‐cobalt‐60 gantry with on‐board 0.35 Tesla MRI with respiratory breath‐hold and daily adaptive re‐planning when anatomically necessary. A median of 40Gy in five fractions was prescribed. The Common Terminology Criteria for Adverse Events v.4.03 was used to score treatment‐related toxicities. Local control (LC), progression‐free survival (PFS), and overall survival (OS) were estimated using Kaplan–Meier method. Results Of the 510 treatments, seventy‐one (13.9%) were adapted. Fatigue, nausea, and pain were the most common acute toxicities. 0.9 and 0% of patients experienced acute grade three and four toxicities, respectively. 5.2 and 2.1% of patients experienced late grade three and four toxicities, respectively. After a median follow‐up of 20.4 months, the 2‐year LC rate was 74% on a per‐lesion basis. Two‐year LC was 96% for lesions that were treated with BED10≥100 versus 69% for BED10, Implementing stereotactic body radiotherapy for abdominal and pelvic tumors has been limited by risk for treatment‐related gastrointestinal toxicity. In the largest reported clinical series to date of stereotactic magnetic resonance image‐guided adaptive radiotherapy, favorable local control and progression‐free survival were observed with minimal morbidity.

The use of kilovoltage cone‐beam computed tomography (kV‐CBCT) or megavoltage computed tomography (MVCT) for image guidance prior to lung stereotactic body radiation therapy (SBRT) is common clinical practice. We demonstrate that under equivalent respiratory conditions, image guidance using both kV‐CBCT and MVCT may result in the inadequate estimation of the range of target motion under free‐breathing (FB) conditions when standard low‐density window and levels are used. Two spherical targets within a respiratory motion phantom were imaged using both long‐exhale (LE) and sinusoidal respiratory traces. MVCT and kV‐CBCT images were acquired and evaluated for peak‐to‐peak amplitudes of 10 or 20 mm in the cranial‐caudal direction, and with 2, 4 or 5 s periods. All images were visually inspected for artifacts and conformity to the ITV for each amplitude, period, trace‐type, and target size. All LE respiratory traces required a lower threshold HU window for MVCT and kV‐CBCT compared to sinusoidal traces to obtain 100% volume conformity compared with the theoretical ITV (ITVT). Excess volume was less than 2% for all kV‐CBCT contours regardless of trace‐type, breathing period, or amplitude, while the maximum excess volume for MVCT was 48%. Adjusting window and level to maximize conformity with the ITVT is necessary to reduce registration uncertainty to less than 5 mm. To fully capture target motion with either MVCT or kV‐CBCT, substantial changes in HU levels up to −600 HU are required which may not be feasible clinically depending on the target's location and surrounding tissue contrast. This registration method, utilizing a substantially decreased window and level compared to standard low‐density settings, was retrospectively compared to the automated registration algorithm for five lung SBRT patients exposed to pre‐treatment kV‐CBCT image guidance. Differences in registrations in the super‐inferior (SI) direction greater than the commonly used ITV to PTV margin of 5 mm were encountered for several cases. In conclusion, pre‐treatment image guidance for lung SBRT targets using MVCT or kV‐CBCT is unlikely to capture the full extent of target motion as defined by the ITVT and additional caution is warranted to avoid registration errors for small targets and patients with LE respiratory traces.

BACKGROUND To evaluate the impact of the planning target volume (PTV) density on treatment planning for lung Stereotactic Body Radiation Therapy (SBRT). MATERIAL AND METHODS The PTV coverage was analyzed in two groups of 40 lung SBRT patients. One group had PTV density 0.5 g/cm3. The treatments were planned in Pinnacle 9.10, using the collapsed cone convolution (CCC) algorithm. The prescribed dose was 60 Gy to the PTV in 4-8 fractions. Respecting constraint for the PTV coverage (D98% > 95%), we compared changes in the isodose line prescription, the number of monitor units (MU), maximum dose (Dmax), irradiated volume covered with 30 Gy (V30Gy), and the optimization planning volume (OPV). RESULTS For the same median values of the PTV coverage (98.3%), the differences are presented with median values between lower and higher density than 0.5 g/cm3. The isodose line prescription was 83 vs. 90% (p

This study used the visualization of hypo‐intense regions on liver‐specific MRI to directly quantify stereotactic body radiation therapy (SBRT) spatial delivery accuracy. Additionally, the interfractional motion of the liver region was determined and compared with the MRI‐based evaluation of liver SBRT spatial treatment delivery accuracy. Primovist®‐enhanced MRI scans were acquired from 17 patients, 8–12 weeks following the completion of liver SBRT treatment. Direct visualization of radiation‐induced focal liver reaction in the form of hypo‐intensity was determined. The auto‐delineation approach was used to localize these regions, and center‐of‐mass (COM) discrepancy was quantified between the MRI hypo‐intensity and the CT‐based treatment plan. To assess the interfractional motion of the liver region, a planning CT was registered to a Cone Beam CT obtained before each treatment fraction. The interfractional motion assessed from this approach was then compared against the localized hypo‐intense MRI regions. The mean ± SD COM discrepancy was 1.4 ± 1.3 mm in the left‐right direction, 2.6 ± 1.8 mm in an anteroposterior direction, and 1.9 ± 2.6 mm in the craniocaudal direction. A high correlation was observed between interfractional motion of visualized hypo‐intensity and interfractional motion of planning treatment volume (PTV); the quantified Pearson correlation coefficient was 0.96. The lack of correlation was observed between Primovist® MRI‐based spatial accuracy and interfractional motion of the liver, where Pearson correlation coefficients ranged from −0.01 to −0.26. The highest random and systematic errors quantified from interfractional motion were in the craniocaudal direction. This work demonstrates a novel framework for the direct evaluation of liver SBRT spatial delivery accuracy.

Purpose. To evaluate immunological status in patients with metastatic forms of solid tumors before and at different intervals after stereotactic body radiation therapy (SBRT) of metastatic lesions depending on the dose and the number of irradiated metastasis. Materials and methods. A quantitative assessment and analysis of blood immunological parameters was conducted before irradiation, via 3-4 weeks and via 6-8 weeks after SBRT in patients with malignant tumors with oligometastases in the liver and lungs, in groups with a total focal dose (TFD ≤ 45 Gy ) and TFD> 45 Gy, and also in groups with irradiation of one metastases and two or more. All peripheral blood samples were analyzed by flow cytometry. Statistical analysis was performed using Friedman and Nemenyi criteria. Results. 3-4 weeks after the end of SBRT, when using higher doses (TFD> 45 Gy), we observed statistically significant increase of T-lymphocytes (CD3+CD19-); T-helpers (CD3+CD4+); activated T-helpers (CD3+CD4+HLA-DR+); activated cytotoxic T-lymphocytes (CD3+СD8+HLA-DR+). Decreasing of B-lymphocytes (CD3+CD19-) was observed in both dose groups (TFD ≤ 45 Gy and TFD > 45 Gy). We also noted the activation of the T-cell link of immunity both in the group with irradiation of one metastatic lesion, and in the group where 2 or more metastases were exposed to irradiation. Conclusion. Using of higher doses of SBRT is associated with a more activated antitumor T-cell immune response, while the analysis of groups of patients with different ammount of irradiated metastasis currently requires further research.

Stereotactic body radiation therapy currently occupies its place in the complex treatment of cancer patients with liver metastases. It is assumed that certain groups of patients with breast cancer can benefit from the use of this method, which can be converted into improved overall survival and survival rates without signs of progression of the process. Purpose of the study was to evaluate the efficacy and tolerability of stereotactic radiotherapy in patients with breast cancer metastases in the liver. We have analyzed the results of using stereotactic radiotherapy in 25 breast cancer patients with 43 liver metastases. The treatment was carried out in 3 fractions with a fraction dose of 10-15 Gy and a total dose of 30-45 Gy. Growth of the irradiated lesions was recorded only in 1 case out of 43 metastases (2,3%) and 25 (4%) patients. 1-, 3- and 5-year overall survival rates from the moment of stereotactic radiotherapy were 82,9%, 62% and 38,7%, respectively. Long-term post-radiation adverse events were observed in 8% of cases and did not have a significant effect on the quality of life and the possibility of antitumor treatment. So stereotactic radiotherapy can be recommended as a relatively safe and highly effective method of elimination of breast cancer liver metastases. Taking into account the high achieved local control, further studies on dose escalation in this group of patients are not required.

Background Historically, IBD has been thought to increase the underlying risk of radiation related toxicity in the treatment of prostate cancer. In the modern era, contemporary radiation planning and delivery may mitigate radiation-related toxicity in this theoretically high-risk cohort. This is the first manuscript to report clinical outcomes for men diagnosed with prostate cancer and underlying IBD curatively treated with stereotactic body radiation therapy (SBRT). Methods A large institutional database of patients (n = 4245) treated with SBRT for adenocarcinoma of the prostate was interrogated to identify patients who were diagnosed with underlying IBD prior to treatment. All patients were treated with SBRT over five treatment fractions using a robotic radiosurgical platform and fiducial tracking. Baseline IBD characteristics including IBD subtype, pre-SBRT IBD medications, and EPIC bowel questionnaires were reviewed for the IBD cohort. Acute and late toxicity was evaluated using the CTCAE version 5.0. Results A total of 31 patients were identified who had underlying IBD prior to SBRT for the curative treatment of prostate cancer. The majority (n = 18) were diagnosed with ulcerative colitis and were being treated with local steroid suppositories for IBD. No biochemical relapses were observed in the IBD cohort with early follow up. High-grade acute and late toxicities were rare (n = 1, grade 3 proctitis) with a median time to any GI toxicity of 22 months. Hemorrhoidal flare was the most common low-grade toxicity observed (n = 3). Conclusion To date, this is one of the largest groups of patients with IBD treated safely and effectively with radiation for prostate cancer and the only review of patients treated with SBRT. Caution is warranted when delivering therapeutic radiation to patients with IBD, however modern radiation techniques appear to have mitigated the risk of GI side effects.

Background and Purpose Stereotactic body radiation therapy delivered using MR-guided radiotherapy (MRgRT) and automatic breathold gating has shown to improve overall survival for locally advanced pancreatic cancer (LAPC) patients. The goal of our study was to evaluate feasibility of treating LAPC patients using abdominal compression (AC) and impact of potential intrafraction motion on planned dose on a 1.5T MR-linac. Methods & Materials Ten LAPC patients were treated with MRgRT to 50 Gy in 5 fractions with daily online plan adaptation and AC. Three orthogonal plane cine MRI were acquired to assess stability of AC pressure in minimizing tumor motion. Three sets of T2w MR scans, pre-treatment (MRIpre), verification (MRIver) and post-treatment (MRIpost) MRI, were acquired for every fraction. A total of 150 MRIs and doses were evaluated. Impact of intrafraction organ motion was evaluated by propagating pre-treatment plan and structures to MRIver and MRIpost, editing contours and recalculating doses. Gross tumor volume (GTV) coverage and organs-at-risk (OARs) doses were evaluated on MRIver and MRIpost. Results Median total treatment time was 75.5 (49–132) minutes. Median tumor motion in AC for all fractions was 1.7 (0.7–7), 2.1 (0.6–6.3) and 4.1 (1.4–10.0) mm in anterior-posterior, left–right and superior-inferior direction. Median GTV V50Gy was 78.7%. Median D5cm3 stomach_duodenum was 24.2 (18.4–29.3) Gy on MRIver and 24.2 (18.3–30.5) Gy on MRIpost. Median D5cm3 small bowel was 24.3 (18.2–32.8) Gy on MRIver and 24.4 (16.0–33.6) Gy on MRIpost. Conclusion Dose-volume constraints for OARs were exceeded for some fractions on MRIver and MRIpost. Longer follow up is needed to see the dosimetric impact of intrafraction motion on gastrointestinal toxicity.

A first‐time survey across 15 cancer centers in Ontario, Canada, on the current practice of patient‐specific quality assurance (PSQA) for intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) delivery was conducted. The objectives were to assess the current state of PSQA practice, identify areas for potential improvement, and facilitate the continued improvement in standardization, consistency, efficacy, and efficiency of PSQA regionally. The survey asked 40 questions related to PSQA practice for IMRT/VMAT delivery. The questions addressed PSQA policy and procedure, delivery log evaluation, instrumentation, measurement setup and methodology, data analysis and interpretation, documentation, process, failure modes, and feedback. The focus of this survey was on PSQA activities related to routine IMRT/VMAT treatments on conventional linacs, including stereotactic body radiation therapy but excluding stereotactic radiosurgery. The participating centers were instructed to submit answers that reflected the collective view or opinion of their department and represented the most typical process practiced. The results of the survey provided a snapshot of the current state of PSQA practice in Ontario and demonstrated considerable variations in the practice. A large majority (80%) of centers performed PSQA measurements on all VMAT plans. Most employed pseudo‐3D array detectors with a true composite (TC) geometry. No standard approach was found for stopping or reducing frequency of measurements. The sole use of delivery log evaluation was not widely implemented, though most centers expressed interest in adopting this technology. All used the Gamma evaluation method for analyzing PSQA measurements; however, no universal approach was reported on how Gamma evaluation and pass determination criteria were determined. All or some PSQA results were reviewed regularly in two‐thirds of the centers. Planning related issues were considered the most frequent source for PSQA failures (40%), whereas the most frequent course of action for a failed PSQA was to review the result and decide whether to proceed to treatment.

The use of stereotactic body radiation therapy (SBRT) to treat many canine tumors is rapidly expanding. However, published studies are lacking regarding use of SBRT for management of canine anal sac adenocarcinoma (ASAC), primarily due to concerns regarding intolerable late effects. The objective of this retrospective, pilot study was to describe the efficacy and safety profile of coarse fractions administered with an SBRT regime to manage a group of dogs with ASAC. A total of 12 dogs with ASAC that received SBRT as a component of their treatment were sampled. Three patients had macroscopic primary tumors irradiated, while nine patients received SBRT following incomplete surgical resection. Seven patients also received metastatic regional lymph node irradiation. Primary tumor and nodal irradiation sites received three fractions totaling 22-24 Gy and 22.5-24 Gy, respectively, over three consecutive days. All patients developed acute effects including mild colitis, alopecia, and erythema. Late effects included alopecia, variable dermal pigmentation and leuko- or melanotrichia within radiation fields, and rectal stricture in one patient. A median progression free survival time of 549 days and median survival time of 991 days were achieved in this study. These results should be considered preliminary data suggesting that coarse fractionation administered with an SBRT technique is a safe and effective treatment regime for the management of canine ASAC, with the aim to conduct prospective studies in the future.

Purpose The purpose of the current study was threefold: (a) investigate the impact of the variations (errors) in spot sizes in robustly optimized pencil beam scanning (PBS) proton‐based stereotactic body radiation therapy (SBRT) lung plans, (b) evaluate the impact of spot sizes and position errors simultaneously, and (c) assess the overall effect of spot size and position errors occurring simultaneously in conjunction with either setup or range errors. Methods In this retrospective study, computed tomography (CT) data set of five lung patients was selected. Treatment plans were regenerated for a total dose of 5000 cGy(RBE) in 5 fractions using a single‐field optimization (SFO) technique. Monte Carlo was used for the plan optimization and final dose calculations. Nominal plans were normalized such that 99% of the clinical target volume (CTV) received the prescription dose. The analysis was divided into three groups. Group 1: The increasing and decreasing spot sizes were evaluated for ±10%, ±15%, and ±20% errors. Group 2: Errors in spot size and spot positions were evaluated simultaneously (spot size: ±10%; spot position: ±1 and ±2 mm). Group 3: Simulated plans from Group 2 were evaluated for the setup (±5 mm) and range (±3.5%) errors. Results Group 1: For the spot size errors of ±10%, the average reduction in D99% for −10% and +10% errors was 0.7% and 1.1%, respectively. For −15% and +15% spot size errors, the average reduction in D99% was 1.4% and 1.9%, respectively. The average reduction in D99% was 2.1% for −20% error and 2.8% for +20% error. The hot spot evaluation showed that, for the same magnitude of error, the decreasing spot sizes resulted in a positive difference (hotter plan) when compared with the increasing spot sizes. Group 2: For a 10% increase in spot size in conjunction with a −1 mm (+1 mm) shift in spot position, the average reduction in D99% was 1.5% (1.8%). For a 10% decrease in spot size in conjunction with a −1 mm (+1 mm) shift in spot position, the reduction in D99% was 0.8% (0.9%). For the spot size errors of ±10% and spot position errors of ±2 mm, the average reduction in D99% was 2.4%. Group 3: Based on the results from 160 plans (4 plans for spot size [±10%] and position [±1 mm] errors × 8 scenarios × 5 patients), the average D99% was 4748 cGy(RBE) with the average reduction of 5.0%. The isocentric shift in the superior–inferior direction yielded the least homogenous dose distributions inside the target volume. Conclusion The increasing spot sizes resulted in decreased target coverage and dose homogeneity. Similarly, the decreasing spot sizes led to a loss of target coverage, overdosage, and degradation of dose homogeneity. The addition of spot size and position errors to plan robustness parameters (setup and range uncertainties) increased the target coverage loss and decreased the dose homogeneity.

Extracranial malignant rhabdoid tumors are rare and aggressive tumors that typically occur in the pediatric age group and have a poor prognosis. Herein, we report a case of a one year and five months old male infant who was referred with the diagnosis of malignant rhabdoid tumor of the liver. Magnetic resonance guided stereotactic body radiotherapy was administered with concomitant chemotherapy. Treatment was well tolerated with no severe acute side effects. A 40.8% volumetric reduction of the tumor was observed at the last fraction of MR guided radiotherapy.

Systematic review for the treatment of high-risk prostate cancer (HR-PCa, D'Amico classification risk system) with external body radiation therapy (EBRT)+brachytherapy-boost (BT-boost) or with EBRT+stereotactic body RT-boost (SBRT-boost). In March 2020, 391 English citations on PubMed matched with search terms "high risk prostate cancer boost". Respectively 9 and 48 prospective and retrospective studies were on BT-boost and 7 retrospective studies were on SBRT-boost. Two SBRT-boost trials were prospective. Only one study (ASCENDE-RT) directly compared the gold standard treatment [dose-escalation (DE)-EBRT+androgen deprivation treatment (ADT)] versus EBRT+ADT+BT-boost. Biochemical control rates at 9 years were 83% in the experimental arm versus 63% in the standard arm. Cumulative incidence of late grade 3 urinary toxicity in the experimental arm and in the standard arm was respectively 18% and 5%. Two recent studies with HR-PCa (National Cancer Database) demonstrated better overall survival with BT-boost (low dose rate LDR or high dose rate HDR) compared with DE-EBRT. These recent findings demonstrate the superiority of EBRT+BT-boost+ADT versus DE-EBRT+ADT for HR-PCa. It seems that EBRT+BT-boost+ADT could now be considered as a gold standard treatment for HR-PCa. HDR or LDR are options. SBRT-boost represents an attractive alternative, but the absence of randomised trials does not allow us to conclude for HR-PCa. Prospective randomised international phase III trials or meta-analyses could improve the level of evidence of SBRT-boost for HR-PCa.