Search

Background: Robotic radiosurgery treatments allow for precise non‐coplanar beam delivery by utilizing a robot equipped with a linac that traverses through a set of predetermined nodes. High quality treatment plans can be produced but treatment times can grow large, with one substantial component being the robot traversal time. Purpose: The aim of this study is to reduce the treatment time for robotic radiosurgery treatments by introducing algorithms for reducing the robot traversal time. The algorithms are integrated into a commercial treatment planning system. Methods: First, an optimization framework for robotic radiosurgery planning is detailed, including a heuristic optimization method for node selection. Second, two methods aimed at reducing the traversal time are introduced. One utilizes a centrality measure focusing on the structure of the node network, while the other is based on the direct computation of traversal times during optimization. A comparison between plans with and without the time‐reducing algorithms is made for three brain cases and one liver case with basis in treatment time, plan quality, monitor units, and network structure of the selected nodes. Results: Large decreases in traversal times are obtained by the traversal time reducing algorithms, with reductions of up to 49 % in the brain cases and 31 % in the liver case. The resulting reductions in treatment times are up to 30 % and 13 %, respectively. Small differences in plan quality are observed, with similar dose‐volume histograms, dose distributions, and conformity/gradient indices. Conclusions: The total treatment time of the robotic radiosurgery treatments can be reduced by selecting nodes with more efficient robot traversal paths, while maintaining plan quality. [ABSTRACT FROM AUTHOR]

Background: Image‐guided radiation‐therapy (IGRT)‐based robotic radiosurgery using magnetic resonance imaging (MRI)‐only simulation could allow for improved target definition with highly conformal radiotherapy treatments. Fiducial marker (FM)‐based alignment is used with robotic radiosurgery treatments of sites such as the prostate because it aids in accurate target localization. Synthetic CT (sCT) images are generated in the MRI‐only workflow but FMs used for IGRT appear as signal voids in MRIs and do not appear in MR‐generated sCTs, hindering the ability to use sCTs for fiducial‐based IGRT. Purpose: In this study we evaluate the fiducial tracking accuracy for a novel artificial fiducial insertion method in sCT images that allows for fiducial marker tracking in robotic radiosurgery, using MRI‐only simulation imaging (MRI‐only workflow). Methods: Artificial fiducial markers were inserted into sCT images at the site of the real marker implantation as visible in MRI. Two phantoms were used in this study. A custom anthropomorphic pelvis phantom was designed to validate the tracking accuracy for a variety of artificial fiducials in an MRI‐only workflow. A head phantom containing a hidden target and orthogonal film pair inserts was used to perform end‐to‐end tests of artificial fiducial configurations inserted in sCT images. The setup and end‐to‐end targeting accuracy of the MRI‐only workflow were compared to the computed tomography (CT)‐based standard. Each phantom had six FMs implanted with a minimum spacing of 2 cm. For each phantom a bulk‐density sCT was generated, and artificial FMs were inserted at the implantation location. Several methods of FM insertion were tested including: (1) replacing HU with a fixed value (10000HU) (voxel‐burned); (2) using a representative fiducial image derived from a linear combination of fiducial templates (composite‐fiducial); (3) computationally simulating FM signal voids using a digital phantom containing FMs and inserting the corresponding signal void into sCT images (simulated‐fiducial). All tests were performed on a CyberKnife system (Accuray, Sunnyvale, CA). Treatment plans and digital‐reconstructed‐radiographs were generated from the original CT and sCTs with embedded fiducials and used to align the phantom on the treatment couch. Differences in the initial phantom alignment (3D translations/rotations) and tracking parameters between CT‐based plans and sCT‐based plans were analyzed. End‐to‐end plans for both scenarios were generated and analyzed following our clinical protocol. Results: For all plans, the fiducial tracking algorithm was able to identify the fiducial locations. The mean FM‐extraction uncertainty for the composite and simulated FMs was below 48% for fiducials in both the anthropomorphic pelvis and end‐to‐end phantoms, which is below the 70% treatment uncertainty threshold. The total targeting error was within tolerance (<0.95 mm) for end‐to‐end tests of sCT images with the composite and head‐on simulated FMs (0.26, 0.44, and 0.35 mm for the composite fiducial in sCT, head‐on simulated fiducial in sCT, and fiducials in original CT, respectively. Conclusions: MRI‐only simulation for robotic radiosurgery could potentially improve treatment accuracy and reduce planning margins. Our study has shown that using a composite‐derived or simulated FM in conjunction with sCT images, MRI‐only workflow can provide clinically acceptable setup accuracy in line with CT‐based standards for FM‐based robotic radiosurgery. [ABSTRACT FROM AUTHOR]

Abstract Objective To investigate the long‐term safety and efficacy of high‐dose radiotherapy after 3D‐printed vertebral body implantation in the treatment of spinal tumors. Methods Thirty‐three participants were recruited between July 2017 and August 2019. 3D‐printed vertebral bodies were implanted in each participant, followed by postoperative robotic stereotactic radiosurgery at a dose of 35–40 Gy/5f. The tolerance of the 3D‐printed vertebral body and the participant to the high‐dose radiotherapy were evaluated. In addition, the local control of tumor and the local progression‐free survival of the study participants following 3D‐printed vertebral body implantation and high‐dose radiotherapy were measured as indexes of effectiveness. Results Of the 33 participants included in the study, 30, including three participants (10%) with esophagitis of grade 3 or above and two participants (6.7%) with advanced radiation nerve injury, successfully underwent postoperative high‐dose radiotherapy. The median follow‐up was 26.7 months, and IQR was 15.9 months. Most participants had primary bone tumors with 27 cases (81.8%), and the rest had bone metastases in six cases (18.2%). After high‐dose radiotherapy, the 3D‐printed vertebrae maintained good vertebral stability and exhibited histocompatibility, without implant fractures. The local control rates were 100%, 88%, and 85% 6 months, 1 year, and 2 years after high‐dose radiotherapy, respectively. Tumors recurred in four participants (12.1%) during the follow‐up period. The median local progression‐free survival after treatment was 25.7 months, with a range of 9.6–33.0 months. Conclusion High‐dose radiotherapy for spinal tumors after 3D‐printed vertebral body implantation is feasible, elicits low toxicity, and yields satisfactory tumor control.

Background and purpose: Preoperative partial breast irradiation (PBI) has got the advantage of treating a well-defined target. We report the results of the phase II ROCK trial (NCT03520894), enrolling early breast cancer (BC) patients treated with preoperative robotic radiosurgery (prRS), in terms of acute and early late toxicity, disease control, and cosmesis. Material and methods: The study recruited between 2018 and 2021 at our Radiation Oncology Unit. Eligible patients were 50 + years old BC, hormonal receptors positive/human epidermal growth factor receptor 2 negative (HR+/HER2-), sized up to 25 mm. The study aimed to prospectively assess the toxicity and feasibility of a robotic single 21 Gy-fraction prRS in preoperative setting. Results: A total of 70 patients were recruited and 22 patients were successfully treated with pRS. Overall, three G1 adverse events (13.6 %) were recorded within 7 days from prRS. Three events (13.6 %) were recorded between 7 and 30 days, one G2 breast oedema and two G1 breast pain. No acute toxicity greater than G2 was recorded. Five patients experienced early late G1 toxicity. One patient reported G2 breast induration. No early late toxicity greater than G2 was observed. At a median follow up of 18 months (range 6–29.8), cosmetic results were scored excellent/good and fair in 14 and 5 patients, respectively, while 3 patients experienced a poor cosmetic outcome. Conclusions: ROCK trial showed that a single 21 Gy dose prRS represents a feasible technique for selected patients affected by early BC, showing an acceptable preliminary toxicity profile.

Objective: Treatment for meningiomas involving the superior sagittal sinus (SSS) is challenging and proved to be associated with higher risks compared to other brain locations. Therapeutical strategies may be either microsurgical (sub-)total resection or adjuvant radiation, or a combination of both. Thrombosis or SSS occlusion following resection or radiosurgery needs to be further elucidated to assess whether single or combined treatment is superior. We here present tumor control and side effect data of robotic radiosurgery (RRS) in combination with or without microsurgery. Methods: From our prospective database, we identified 137 patients with WHO grade I meningioma involving the SSS consecutively treated between 2005 and 2020. Treatment decisions were interdisciplinary. Patients underwent RRS as initial/solitary treatment (group 1), as adjuvant treatment after subtotal resection (group 2), or due to recurrent tumor growth after preceding microsurgery (group 3). Positive tumor response was assessed by MRI and defined as reduction of more than 50% of volume. Study endpoints were time to recurrence (TTR), time to RRS, risk factors for decreased survival, and side effects. Overall and specific recurrence rates for treatment groups were analyzed. Side effect data included therapy-related morbidity during follow-up (FU). Results: A total of 137 patients (median age, 58.3 years) with SSS meningiomas WHO grade I were analyzed: 51 patients (37.2%) in group 1, 15 patients (11.0%) in group 2, and 71 patients (51.8%) in group 3. Positive MR (morphological response) to therapy was achieved in 50 patients (36.4%), no response was observed in 25 patients (18.2%), and radiological tumor progression was detected in 8 patients (5.8%). Overall 5-year probability of tumor recurrence was 15.8% (median TTR, 41.6 months). Five-year probabilities of recurrence were 0%, 8.3.%, and 21.5% for groups 1-3 (p = 0.06). In multivariate analysis, tumor volume was significantly associated with extent of SSS occlusion (p = 0.026) and sex (p = 0.011). Tumor volume significantly correlated with TTR (p = 0.0046). Acute sinus venous thrombosis or venous congestion-associated bleedings did not occur in any of the groups. Conclusion: RRS for grade I meningiomas with SSS involvement represents a good option as first-line treatment, occasionally also in recurrent and adjuvant scenarios as part of a multimodal treatment strategy. [ABSTRACT FROM AUTHOR]

ObjectiveTreatment for meningiomas involving the superior sagittal sinus (SSS) is challenging and proved to be associated with higher risks compared to other brain locations. Therapeutical strategies may be either microsurgical (sub-)total resection or adjuvant radiation, or a combination of both. Thrombosis or SSS occlusion following resection or radiosurgery needs to be further elucidated to assess whether single or combined treatment is superior. We here present tumor control and side effect data of robotic radiosurgery (RRS) in combination with or without microsurgery.MethodsFrom our prospective database, we identified 137 patients with WHO grade I meningioma involving the SSS consecutively treated between 2005 and 2020. Treatment decisions were interdisciplinary. Patients underwent RRS as initial/solitary treatment (group 1), as adjuvant treatment after subtotal resection (group 2), or due to recurrent tumor growth after preceding microsurgery (group 3). Positive tumor response was assessed by MRI and defined as reduction of more than 50% of volume. Study endpoints were time to recurrence (TTR), time to RRS, risk factors for decreased survival, and side effects. Overall and specific recurrence rates for treatment groups were analyzed. Side effect data included therapy-related morbidity during follow-up (FU).ResultsA total of 137 patients (median age, 58.3 years) with SSS meningiomas WHO grade I were analyzed: 51 patients (37.2%) in group 1, 15 patients (11.0%) in group 2, and 71 patients (51.8%) in group 3. Positive MR (morphological response) to therapy was achieved in 50 patients (36.4%), no response was observed in 25 patients (18.2%), and radiological tumor progression was detected in 8 patients (5.8%). Overall 5-year probability of tumor recurrence was 15.8% (median TTR, 41.6 months). Five-year probabilities of recurrence were 0%, 8.3.%, and 21.5% for groups 1–3 (p = 0.06). In multivariate analysis, tumor volume was significantly associated with extent of SSS occlusion (p = 0.026) and sex (p = 0.011). Tumor volume significantly correlated with TTR (p = 0.0046). Acute sinus venous thrombosis or venous congestion-associated bleedings did not occur in any of the groups.ConclusionRRS for grade I meningiomas with SSS involvement represents a good option as first-line treatment, occasionally also in recurrent and adjuvant scenarios as part of a multimodal treatment strategy.

Background: Prospective analysis of oligo-brain metastasis in Indian patients treated with SRS-only treatment. Methods: Between January 2017 and May 2022, 235 patients were screened and 138 histologically proven and radiologically confirmed. One to five brain metastasis patients aged more than 18 years with good Karnofsky performance status (KPS >70) accrued in ethical and scientific committee-approved prospective observational study protocol for treatment with only radiosurgery (SRS) with robotic radiosurgery (CyberKnife, CK) [AIMS IRB: 2020-071; CTRI No: REF/2022/01/050237]. Immobilization was performed with a thermoplastic mask, contrast CT simulation was performed with 0.625 mm slices, fused with T1 contrast/T2 FLAIR MRI images for contouring. Planning target volume (PTV) margin of 2–3 mm and a dose of 20–30 Gy in 1–5 fractions. Response to treatment, new brain lesions free survival, overall survival, and toxicity profile after CK were evaluated. Results: In total, 138 patients with 251 lesions were accrued (median age 59 years (interquartile range [IQR] 49–67 years; female 51%; headache in 34%, motor deficit in 7%, KPS >90 in 56%; lung primary in 44%, breast in 30%; oligo-recurrence in 45%; synchronous oligo-metastases in 33%; adenocarcinoma primary in 83%). One hundred seven patients (77%) received upfront Stereotactic radiotherapy (SRS), 15 (11%) received postoperative SRS, 12 (9%) received whole brain radiotherapy (WBRT) before SRS, and 3 (2%) received WBRT plus SRS boost. The majority had solitary (56%) brain metastasis, 28% had two to three lesions, and 16% had four to five brain lesions. Frontal (39%) was the most common site. Median PTV was 15.5 mL (IQR – 8.1–28.5 mL). Seventy-one (52%) patients were treated with single fractions, 14% with three, and 33% with five fractions. Fraction schedules were 20–2 4 Gy/1fr; 27 Gy/3fr, and 25 Gy/5 fractions (mean BED 74.6 Gy [SD ± 48.1; mean MU 16608], mean treatment time was 49 min (range 17–118 min]. Twelve Gy normal brain volume was 40.8 mL (3.2%) (range 19.3–73.7 mL). At a mean follow-up of 15 months (SD 11.9 months; max 56 months), the mean actuarial OS after SRS-only treatment was 23.7 months (95% confidence interval [CI] 20–28). Further 124 (90%) patients had >3 months, 108 (78%) had >6 months, 65 (47%) had >12 months, and 26 (19%) had >24 months follow-up. Intracranial disease and extracranial disease were controlled in 72 (52.2%) and 60 (43.5%), respectively. "In-field" recurrence, "out-of-field," and "both in and out-of-field" recurrences were in 11%, 42%, and 46%, respectively. At the last follow-up, 55 patients (40%) were alive, 75 (54%) died due to disease progression, and the status of 8 (6%) patients was not known. Among 75 patients who died, 46 (61%) had extracranial disease progression, 12 (16%) had only intracranial progression, and 8 (11%) had unrelated causes. Also, 12/117 (9%) had radiological confirmation of radiation necrosis. Prognostication based on western patients (primary tumor type, number of lesions extracranial disease) showed similar outcomes. Conclusions: SRS alone in brain metastasis is feasible in the Indian subcontinent with similar survival outcomes, recurrence patterns, and toxicity as published in the western literature. Patient selection, dose schedule, and planning need to be standardized to have similar outcomes. WBRT can be safely omitted in Indian patients with oligo-brain metastasis. Western prognostication nomogram is applicable in the Indian patient population. [ABSTRACT FROM AUTHOR]

The IBA myQA® SRS high-resolution solid-state detector was evaluated in the context of robotic radiosurgery delivered using CyberKnife®. The performance was investigated for periodic machine delivery quality assurance (DQA) and patient-specific treatment verification. myQA® SRS is a 140 × 120 mm CMOS matrix with 400 µm resolution, allocated in a cylindrical ABS phantom topped by a hemispheric cap. Evaluations included: periodic DQA tests, angular response, dose-rate dependence and Iris variable aperture collimator field size measurements. For patient-specific QA various intracranial targets were studied (Gamma Index, 3%/1 mm agreement criteria), taking into account also the detector's angular response. Results for periodic DQA were in accordance with the machine commissioning data. Dose-rate dependence was confirmed, and angular response tests resulted in a signal decay >5% when beams were delivered outside a ±50° amplitude cone with respect to the vertical direction. Concerning patient-specific QA, >50° angled beams elimination led to a Gamma Index passing rates improvement ranging between +3% and +115%. IBA myQA® SRS proved to be a suitable device for many CyberKnife® constancy DQA checks, providing high-resolution real-time results. Patient-specific Gamma tests showed high passing rates once angular dependence corrections were performed, even in high complexity treatments such as those for trigeminal neuralgia targets. [ABSTRACT FROM AUTHOR]

A five degree of freedom, robotic, radiosurgical system dedicated to the brain is currently under development. In the proposed design, the machine is entirely self-shielded. The main advantage of a self-shielded system is the simplification of the system's installation, which can reduce the cost of radiosurgery. In this way, more patients can benefit from this minimally invasive and highly effective type of procedure. For technical reasons, space inside the shielded region is limited, which leads to constraints on the design. Here, two axes of rotation move a 3-megavolt linear accelerator around the patient's head at a source axis distance of 400 millimeters (mm), while the integrated patient table is characterized by two additional rotational, and one translational, degrees of freedom. Eight cone collimators of different diameters are available. The system can change the collimator automatically during treatment, using a collimator wheel. Since the linear accelerator can only move with two rotational axes, it is not possible to reposition the beam translationally (as it is in six degrees of freedom robotic radiosurgery). To achieve translational repositioning, it is necessary to move the patient couch. Thus, translational repositioning must be kept to a minimum during treatment. Our goal in this contribution is a preliminary investigation of dose distributions attainable with this type of design. Thus, we do not intend to design and evaluate the treatment planning system itself, but rather to establish that appropriate dose distributions can be achieved with this design under realistic clinical circumstances. Our simulation suggests that dose gradients and conformity for complex target shapes, corresponding to state-of-the-art systems, can be achieved with this construction, although a detailed evaluation of the system itself would be needed in the future.

The aim of this study was to prospectively evaluate stereotactic body radiotherapy (SBRT) with robotic radiosurgery in hepatocellular carcinoma patients with macrovascular invasion (HCC-PVT). Patients with inoperable HCC-PVT, good performance score (PS0-1) and preserved liver function [up to Child-Pugh (CP) B7] were accrued after ethical and scientific committee approval [Clinical trial registry-India (CTRI): 2022/01/050234] for treatment on robotic radiosurgery (M6) and planned with Multiplan (iDMS V2.0). Triple-phase contrast computed tomography (CT) scan was performed for contouring, and gross tumour volume (GTV) included contrast-enhancing mass within main portal vein and adjacent parenchymal disease. Dose prescription was as per risk stratification protocol (22–50 Gy in 5 fractions) while achieving the constraints of mean liver dose <15 Gy, 800 cc liver <8 Gy and the duodenum max of <24 Gy). Response assessment was done at 2 months' follow-up for recanalization. Patient- and treatment-related factors were evaluated for influence in survival function. Between Jan 2017 and May 2022, 318 consecutive HCC with PVT patients were screened and 219 patients were accrued [male 92%, CP score: 5–7 90%, mean age: 63 years (38–85 yrs), Cancer of the Liver Italian Program <3: 84 (40%), 3–6117 (56%), infective aetiology 9.5%, performance status (PS): 0–37%; 1–56%]. Among 209 consecutive patients accrued for SBRT treatment (10 patients were excluded after accrual due to ascites and decompensation), 139 were evaluable for response assessment (>2 mo follow-up). At mean follow-up of 12.21 months (standard deviation: 10.66), 88 (63%) patients expired and 51 (36%) were alive. Eighty-two (59%) patients had recanalization of PVT (response), 57 (41%) patients did not recanalize and 28 (17%) had progressive/metastatic disease prior to response evaluation (<2 months). Mean overall survival (OS) in responders and non-responders were 18.4 [standard error (SE): 2.52] and 9.34 month (SE 0.81), respectively (P < 0.001). Mean survival in patients with PS0, PS1 and PS2 were 17, 11.7 and 9.7 months (P = 0.019), respectively. OS in partial recanalization, bland thrombus and complete recanalization was 12.4, 14.1 and 30.3 months, respectively (P -0.002). Adjuvant sorafenib, Barcelona Clinic Liver Classification stage, gender, age and RT dose did not influence response to treatment. Recanalization rate was higher in good PS patients (P -0.019). OS in patients with response to treatment, in those with no response to treatment, in those who are fit but not accrued and in those who are not suitable were 18.4, 9.34, 5.9 and 2.6 months, respectively (P -<0.001). Thirty-six of 139 patients (24%) had radiation-induced liver disease (RILD) [10 (7.2%) had classic RILD & 26 (19%) had non-classic RILD]. Derangement in CP score (CP score change) by more than 2 was seen in 30 (24%) within 2-month period after robotic radiosurgery. Eighteen (13%) had unplanned admissions, two patients required embolization due to fiducial-related bleeding and 20 (14%) had ascites, of which 9 (6%) patients required abdominocentesis. PVT response or recanalization after SBRT is a statistically significant prognostic factor for survival function in HCC-PVT. [ABSTRACT FROM AUTHOR]

Although robotic radiosurgery offers a flexible arrangement of treatment beams, generating treatment plans is computationally challenging and a time consuming process for the planner. Furthermore, different clinical goals have to be considered during planning and generally different sets of beams correspond to different clinical goals. Typically, candidate beams sampled from a randomized heuristic form the basis for treatment planning. We propose a new approach to generate candidate beams based on deep learning using radiological features as well as the desired constraints. We demonstrate that candidate beams generated for specific clinical goals can improve treatment plan quality. Furthermore, we compare two approaches to include information about constraints in the prediction. Our results show that CNN generated beams can improve treatment plan quality for different clinical goals, increasing coverage from 91.2 to 96.8% for 3,000 candidate beams on average. When including the clinical goal in the training, coverage is improved by 1.1% points.

Purpose: to compare immediate, short-term and long-term treatment outcomes after radical prostatectomy and robotic radiosurgery in patients with localized prostate cancer. Material and methods. The study included 2 groups of patients. Group I patients (n=80) underwent radical surgery (nerve-sparing prostatectomy). Group II patients (n=102) underwent KiberKnife stereotactic robotic radiotherapy. Results. Immediate treatment outcomes after both radical prostatectomy and robotic radiosurgery did not demonstrate increased number of postoperative complications and severe radiation-induced injuries. The PSA level decreased and reached a nadir PSA level immediately after radical prostatectomy. After stereotactic radiation therapy, the PSA level decreased gradually every three months, reaching a nadir within a year. In the group of patients receiving CyberKnife treatment, changes in the prostate volume affected the quality of urination, which was confirmed by the assessment of the volume of residual urine. When comparing the quality of urination in treatment groups using the IPSS scale, the values were comparable. No differences in the 1-year disease-free survival rates between groups were found. However, 60 months later, disease free survival rate was higher by 8.2 % in patients treated with radiosurgery than in patients who underwent radical prostatectomy (p

Objective: Cyberknife robotic radiosurgery (RRS) provides single-session high-dose radiotherapy of brain tumors with a steep dose gradient and precise real-time image-guided motion correction. Although RRS appears to cause more radiation necrosis (RN), the radiometabolic changes after RRS have not been fully clarified. 18F-FET-PET/CT is used to differentiate recurrent tumor (RT) from RN after radiosurgery when MRI findings are indecisive. We explored the usefulness of dynamic parameters derived from 18F-FET PET in differentiating RT from RN after Cyberknife treatment in a single-center study population. Methods: We retrospectively identified brain tumor patients with static and dynamic 18F-FET-PET/CT for suspected RN after Cyberknife. Static (tumor-to-background ratio) and dynamic PET parameters (time-activity curve, time-to-peak) were quantified. Analyses were performed for all lesions taken together (TOTAL) and for brain metastases only (METS). Diagnostic accuracy of PET parameters (using mean tumor-to-background ratio >1.95 and time-to-peak of 20 min for RT as cut-offs) and their respective improvement of diagnostic probability were analyzed. Results: Fourteen patients with 28 brain tumors were included in quantitative analysis. Time-activity curves alone provided the highest sensitivities (TOTAL: 95%, METS: 100%) at the cost of specificity (TOTAL: 50%, METS: 57%). Combined mean tumor-to-background ratio and time-activity curve had the highest specificities (TOTAL: 63%, METS: 71%) and led to the highest increase in diagnosis probability of up to 16% p. – versus 5% p. when only static parameters were used. Conclusions: This preliminary study shows that combined dynamic and static 18F-FET PET/CT parameters can be used in differentiating RT from RN after RRS.

Quantitative retrospective analysis of the normal lung irradiation due to the variations of the ITV volume based on the techniques used for upper lobe (UL), mid lobe (ML), and lower lobe (LL) lung tumours when used with 2-view, 1-view, 0-view based LOT technique on Cyberknife, AveIP on Helical Tomotherapy, and DIBH on VMAT systems. In the treatment of lung tumours, patients medically inoperable or those who are unwilling to undergo surgery have the option to be treated using radiation therapy. There are many motion control techniques available for the treatment of the moving target, such as movement encompassment, respiratory gating, breath-hold, motion reduction, and tumour monitoring. ITV generation is dependent on technique and hence the volume of the PTVs will differ based on the technique used. This study aimed to determine the influence of these ITVs on the irradiated normal lung volume for UL, ML, and LL lung tumours for 23 patients. The mean difference in the PTV volumes generated with the 0-view technique was significant with that of 2-view and DIBH techniques (p-value < 0.04). The mean difference in the PTV volumes generated by 2-view and DIBH was small for UL, ML, and LL tumours. V5 of the combined lung with the 0-view method was 5% compared to the 2-view method for UL tumours (p-value = 0.04) and the same was 9.5%, and 16.8% for ML and LL tumours (p-value < 0.04). In contrast to all other techniques, lung volume parameters V5, V10, V20, and V30 for the 0-view technology were consistently higher irrespective of the tumour location in the lung. The observed maximum mean lung dose (MLD) was 6.2 Gy ± 2.7 Gy with the 0-view technique and the minimum was 3.85 Gy ± 1.75 Gy with the DIBH technique. The difference in MLD between DIBH and 2-view was negligible (p-value = 0.67). The MLD increased for LL tumours from 4 Gy to 6.5 Gy from the 2-view to 0-view technique (p-value = 0.009). There was a significant increase in MLD for LL tumours with the 0-view technique compared to AveIP (1.9 Gy, p-value = 0.04) and DIBH (2.0 Gy, p-value = 0.003) technique. For ML and UL tumours, except for 0-view and 1-view, the difference in the MLD between the rest of the methods was not significant (p-value > 0.11). In the treatment of lung tumour patients with SBRT, this study has demonstrated 2-view with Cyberknife and DIBH with VMAT treatment techniques have optimal normal lung tissue sparing. There was a significant increase in the average lung volume receiving 5%,10%, 20%, and 30% dose when comparing the 1-view, 0-view, AveIP, and DIBH techniques to the 2-view technique. However, DIBH with VMAT was dosimetrically advantageous for ML and LL tumours, while providing significantly shorter treatment times than any other technique studied. [ABSTRACT FROM AUTHOR]

Background: This is a prospective study evaluating the role of stereotactic body radiotherapy (SBRT) with CyberKnife (CK) in Indian patients suffering from hepatocellular carcinoma with portal vein thrombosis (HCC-PVT). Methods: Patients with inoperable HCC-PVT, good performance score (PS), and liver function are accrued for treatment on CK (version M6) and planned with Multiplan (iDMS V2.0). Triple-phase contrast computed tomography (CT) scan was done for contouring, and the gross tumor volume (GTV) included contrast-enhancing mass within main portal vein and adjacent parenchymal disease. Dose prescription was as per-risk stratification protocol (22–50 Gy in 5 fractions) while achieving the constraints of mean liver dose <15 Gy, 800 cc liver <8 Gy, and the duodenum max of ≤24 Gy). Results: Seventy-two HCC-PVT accrued till date (mean age 63 years [38–76 years], 96% male; Child-Pugh [CP] A 84%, B 9%; Barcelona-Clinic Liver Cancer [BCLC] C 96%; PS0-1: 80%, Karnofsky performance score [KPS]>70: 88%; co-morbidities 42%; infective 12%, alcohol intake 31%, adjuvant sorafenib 39%). CP scores 5, 6, 7, and 8 were in 35%, 32%, 8%, and 18%, respectively. Focal disease with portal vein thrombus (PVT) in 21%, liver involvement >50% and <50% in 46% and 32%. Liver cancer study group of Japan staging–based portal vein invasion VP2, VP3, and VP4 in 22%, 29%, and 40%. Cancer of the Liver Italian Programm (CLIP) scores 1, 2, 3, 4, and 5 were in 8%, 26%, 31%, 26%, and 7%, respectively. Mean follow-up was 7.3 months (median 6 months, standard deviation [SD] 6; range 3–30 months). Mean actuarial overall survival (OS) was 11.4 months (SE 1.587; 95% CI: 8–14.2 months). Six months and 12 months actuarial OS 55% and 38%, respectively. At last follow-up, 25/69 (36%) were alive and 44/69 (64%) were dead. Among 54 patients evaluated for response assessment, 23 (30%) had radiological confirmed PVT response, 1 (3%) had response of IVC thrombus, and 30 (42%) had no or minimal response to SBRT. Actuarial OS in responders and non-responders were 14.4 months (95% CI 9.4–19.2) and 7.4 months (95% CI 4.9–9.7), p-value: 0.022. Six and 12 months survival in responders and non-responders were 65.7% and 37% and 49% and 24.6%, respectively. Post-SBRT, 4 (12%) patients underwent transarterial chemoembolization (TACE) 3 patients (8%) and 1 patient (4%) transarterial radioembolization (TARE). Post-CK, (<4 weeks) 2 patients (4%) had decompensation. Conclusions: PVT response or recanalization after SBRT is a statistically significant prognostic factor for survival function in HCC-PVT. [ABSTRACT FROM AUTHOR]

• Assess tumor motion and accuracy of robotic radiosurgery in renal cell carcinoma. • Extensive tumor motion, especially in the superior-inferior direction. • Patients with surgical pretreatment show significantly smaller tumor motion. • The larger the tumor motion, the larger the errors from the breathing model. • Minimum PTV margins of 4.3 mm (SI), 2.6 mm (LR), and 3.0 mm (AP) should be used. Although emerging clinical evidence supports robotic radiosurgery as a highly effective treatment option for renal cell carcinoma (RCC) less than 4 cm in diameter, delivery uncertainties and associated target volume margins have not been studied in detail. We assess intrafraction tumor motion patterns and accuracy of robotic radiosurgery in renal tumors with real-time respiratory tracking to optimize treatment margins. Delivery log files from 165 consecutive treatments of RCC were retrospectively analyzed. Five components were considered for planning target volume (PTV) margin estimation: (a) The model error from the correlation model between patient breath and tumor motion, (b) the prediction error from an algorithm predicting the patient breathing pattern, (c) the targeting error from the treatment robot, (d) the inherent total accuracy of the system for respiratory motion tracking, and (e) the margin required to cover potential target rotation, simulated with PTV rotations up to 10°. The median tumor motion was 10.5 mm , 2.4 mm and 4.4 mm in the superior-inferior, left–right, and anterior-posterior directions, respectively. The root of the sum of squares of all contributions to the system's inaccuracy results in a minimum PTV margin of 4.3 mm , 2.6 mm and 3.0 mm in the superior-inferior, left–right and anterior-posterior directions, respectively, assuming optimal fiducial position and neglecting target deformation. We have assessed kidney motion and derived PTV margins for the treatment of RCC with robotic radiosurgery, which helps to deliver renal treatments in a more consistent manner and potentially further improve outcomes. [ABSTRACT FROM AUTHOR]

The IBA myQA® SRS high-resolution solid-state detector was evaluated in the context of robotic radiosurgery delivered using CyberKnife®. The performance was investigated for periodic machine delivery quality assurance (DQA) and patient-specific treatment verification. myQA® SRS is a 140 × 120 mm CMOS matrix with 400 µm resolution, allocated in a cylindrical ABS phantom topped by a hemispheric cap. Evaluations included: periodic DQA tests, angular response, dose-rate dependence and Iris variable aperture collimator field size measurements. For patient-specific QA various intracranial targets were studied (Gamma Index, 3%/1 mm agreement criteria), taking into account also the detector’s angular response. Results for periodic DQA were in accordance with the machine commissioning data. Dose-rate dependence was confirmed, and angular response tests resulted in a signal decay >5% when beams were delivered outside a ±50° amplitude cone with respect to the vertical direction. Concerning patient-specific QA, >50° angled beams elimination led to a Gamma Index passing rates improvement ranging between +3% and +115%. IBA myQA® SRS proved to be a suitable device for many CyberKnife® constancy DQA checks, providing high-resolution real-time results. Patient-specific Gamma tests showed high passing rates once angular dependence corrections were performed, even in high complexity treatments such as those for trigeminal neuralgia targets.

Purpose: Vasoproliferative tumours (VPT) are a rare but benign entity that can lead to severe visual acuity deterioration. There is no standard of care, and depending on the degree of clinical features, including tumour size and dissemination, visual acuity and subretinal fluid, treatment options include observation, cryotherapy and brachytherapy. Particularly in larger tumours, brachytherapy has advantages over other options, although higher radiation doses and the need for surgical application are disadvantages of this otherwise effective treatment option. CyberKnife radiosurgery might represent an alternative therapeutic option as no surgical intervention is needed and radiation doses are lower. Methods: All patients diagnosed with vasoproliferative tumors who were treated with CyberKnife radiosurgery with a minimum follow‐up time of 12 months were included in this case series. We recorded visual acuity, number of lesions, central retinal thickness with optical coherence tomography (OCT) and reflectivity using A‐scan standardizes echography every three months. Results: A total of four patients with a median age of 34 years (range: 24 – 51) who were observed over an average of 26.5 months (range: 17 – 49 months) matched our inclusion criteria. We appreciated stabilization or increase in visual acuity in all four patients and a regression in tumour thickness with subsequent increase in internal reflectivity as a marker of increasing fibrosis. Conclusion: We observed good visual and functional outcome following CyberKnife therapy for VPT. We believe that further studies should be pursued to evaluate CyberKnife therapy for the treatment of VPT not treatable with cryo‐ or lasertherapy. [ABSTRACT FROM AUTHOR]

Purpose: Robotic radiosurgery offers the flexibility of a robotic arm to enable high conformity to the target and a steep dose gradient. However, treatment planning becomes a computationally challenging task as the search space for potential beam directions for dose delivery is arbitrarily large. We propose an approach based on deep learning to improve the search for treatment beams. Methods: In clinical practice, a set of candidate beams generated by a randomized heuristic forms the basis for treatment planning. We use a convolutional neural network to identify promising candidate beams. Using radiological features of the patient, we predict the influence of a candidate beam on the delivered dose individually and let this prediction guide the selection of candidate beams. Features are represented as projections of the organ structures which are relevant during planning. Solutions to the inverse planning problem are generated for random and CNN‐predicted candidate beams. Results: The coverage increases from 95.35% to 97.67% for 6000 heuristically and CNN‐generated candidate beams, respectively. Conversely, a similar coverage can be achieved for treatment plans with half the number of candidate beams. This results in a patient‐dependent reduced averaged computation time of 20.28%–45.69%. The number of active treatment beams can be reduced by 11.35% on average, which reduces treatment time. Constraining the maximum number of candidate beams per beam node can further improve the average coverage by 0.75 percentage points for 6000 candidate beams. Conclusions: We show that deep learning based on radiological features can substantially improve treatment plan quality, reduce computation runtime, and treatment time compared to the heuristic approach used in clinics. [ABSTRACT FROM AUTHOR]

Introduction: Following the resection of brain metastases (BM), whole-brain radiotherapy (WBRT) is a long-established standard of care. Its position was recently challenged by the less toxic single-session radiosurgery (SRS) or fractionated stereotactic radiotherapy (FSRT) of the resection cavity, reducing dose exposure of the healthy brain. Patients and Methods: We analyzed 101 patients treated with either SRS/FSRT (n = 50) or WBRT (n = 51) following BM resection over a 5-year period. Propensity score adjustment was done for age, total number of BM, timepoint of BM diagnosis, controlled primary and extracranial metastases. A Cox Proportional Hazards model with univariate and multivariate analysis was fitted for overall survival (OS), local control (LC) and distant brain control (DBC). Results: Median patient age was 61 (interquartile range, IQR: 56–67) years and the most common histology was non-small cell lung cancer, followed by breast cancer. 38% of the patients had additional unresected BM. Twenty-four patients received SRS, 26 patients received FSRT and 51 patients received WBRT. Median OS in the SRS/FSRT subgroup was not reached (IQR NA−16.7 months) vs. 12.6 months (IQR 21.3–4.4) in the WBRT subgroup (hazard ratio, HR 3.3, 95%-CI: [1.5; 7.2] p < 0.002). Twelve-months LC-probability was 94.9% (95%-CI: [88.3; 100.0]) in the SRS subgroup vs. 81.7% (95%-CI: [66.6; 100.0]) in the WBRT subgroup (HR 0.2, 95%-CI: [0.01; 0.9] p = 0.037). Twelve-months DBC-probabilities were 65.0% (95%-CI: [50.8; 83.0]) and 58.8% (95%-CI: [42.9; 80.7]), respectively (HR 1.4, 95%-CI: [0.7; 2.7] p = 0.401). In propensity score-adjusted multivariate analysis, incomplete resection negatively impacted OS (HR 3.9, 95%-CI: [2.0;7.4], p < 0.001) and LC (HR 5.4, 95%-CI: [1.3; 21.9], p = 0.018). Excellent clinical performance (HR 0.4, 95%-CI: [0.2; 0.9], p = 0.030) and better graded prognostic assessment (GPA) score (HR 0.4, 95%-CI: [0.2; 1.0], p = 0.040) were prognostic of superior OS. A higher number of BM was associated with a greater risk of developing new distant BM (HR 5.6, 95%-CI: [1.0; 30.4], p = 0.048). In subgroup analysis, larger cavity volume (HR 1.1, 95%-CI: [1.0; 1.3], p = 0.033) and incomplete resection (HR 12.0, 95%-CI: [1.2; 118.3], p = 0.033) were associated with inferior LC following SRS/FSRT. Conclusion: This is the first propensity score-adjusted direct comparison of SRS/FSRT and WBRT following the resection of BM. Patients receiving SRS/FSRT showed longer OS and LC compared to WBRT. Future analyses will address the optimal choice of safety margin, dose and fractionation for postoperative stereotactic RT of the resection cavity. [ABSTRACT FROM AUTHOR]

Introduction: Stereotactic radiosurgery (SRS) is becoming more frequently used for patients with multiple brain metastases (BMs). Single-isocenter volumetric modulated arc therapy (SI-VMAT) is an emerging alternative to dedicated systems such as CyberKnife (CK). We present a dosimetric comparison between CyberKnife M6 and SI-VMAT, planned at RayStation V8B, for the simultaneous SRS of five or more BM. Patients and Methods: Twenty treatment plans of CK-based single-session SRS to ≥5 brain metastases were replanned using SI-VMAT for delivery at an Elekta VersaHD linear accelerator. Prescription dose was 20 or 18 Gy, conformally enclosing at least 98% of the total planning target volume (PTV), with PTV margin-width adapted to the respective SRS technique. Comparatively analyzed quality metrics included dose distribution to the healthy brain (HB), including different isodose volumes, conformity, and gradient indices. Estimated treatment time was also compared. Results: Median HB isodose volumes for 3, 5, 8, 10, and 12 Gy were consistently smaller for CK-SRS compared to SI-VMAT (p < 0.001). Dose falloff outside the target volume, as expressed by the gradient indices GI_high and GI_low, was consistently steeper for CK-SRS compared to SI-VMAT (p < 0.001). CK-SRS achieved a median GI_high of 3.1 [interquartile range (IQR), 2.9–1.3] vs. 5.0 (IQR 4.3–5.5) for SI-VMAT (p < 0.001). For GI_low, the results were 3.0 (IQR, 2.9–3.1) for CK-SRS vs. 5.6 (IQR, 4.3–5.5) for SI-VMAT (p < 0.001). The median conformity index (CI) was 1.2 (IQR, 1.1–1.2) for CK-SRS vs. 1.5 (IQR, 1.4–1.7) for SI-VMAT (p < 0.001). Estimated treatment time was shorter for SI-VMAT, yielding a median of 13.7 min (IQR, 13.5–14.0) compared to 130 min (IQR, 114.5–154.5) for CK-SRS (p < 0.001). Conclusion: SI-VMAT offers enhanced treatment efficiency in cases with multiple BM, as compared to CyberKnife, but requires compromise regarding conformity and integral dose to the healthy brain. Additionally, delivery at a conventional linear accelerator (linac) may require a larger PTV margin to account for delivery and setup errors. Further evaluations are warranted to determine whether the detected dosimetric differences are clinically relevant. SI-VMAT could be a reasonable alternative to a dedicated radiosurgery system for selected patients with multiple BM. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to report CyberKnife experience in hepatocellular carcinoma (HCC) and liver metastasis (LM). Materials and Methods: Fifty liver lesions in 31 consecutive patients with liver lesion [mean age 54.5 years (range 32-81 years), 77% were male patient, GTV 90cc in 8 patients respectively. Eighty percentage (25/31) had prior treatment (chemotherapy 18 patient & TACE in 7 patients). Dosage schedule was 21-45Gy/3# (mean PTV dose 33Gy, Prescription isodose 84%, target coverage 94%). Mean CI, nCI & HI were 1.19, 1.31 & 1.18 respectively. Mean liver dose was 5.4 Gy, 800 cc liver dose 11.1 Gy; Results: At mean follow-up of 12.5 months (range 1.9–44.6 months), 19 patients were expired and 12 were alive (nine patient with stable disease, two local progression, and one with metastasis). Median overall survival (OS) of all patients are 9 months (1.9–44.6 months), in HCC patients 10.5 months (2.1–44.6 months) and MT 6.5 months (1.9–24.6 months) respectively. Gr-I-II GI toxicities were in 11/50 (22%) patients. OS was influenced by PS (Karnofsky Performance Status 70–80 vs. 90–100: 9.9 vs. 16.4; P = 0.024), Child-Pugh (CP A/B vs. C: 23.6 vs. 6.5; P = 0.069), cirrhosis (only fatty liver vs. diffuse cirrhosis: 17.8 vs. 10.6; P = 0.003), prior treatment (no Rx vs. prior Rx: 30.1 vs. 8.2; P = 0.08), number of lesions (single vs. multiple: 16.4 vs. 6.9; P = 0.001), and target volume (90 cc: 24.6 vs. 11.2; P = 0.03). Conclusion: Stereotactic body radiation therapy is a safe and effective treatment. Patient related factors such as performance status, Child-Pugh classification, cirrhosis status, prior treatment, number of liver lesion & target volume (GTV) influence the survival functions.

For daily CyberKnife QA a Winston-Lutz-Test (Automated-Quality-Assurance, AQA) is used to determine sub-millimeter deviations in beam delivery accuracy. This test is performed using gafchromic film, an extensive and user-dependent method requiring the use of disposables. We therefore analyzed the usability and accuracy of high-resolution detector arrays. We analyzed a liquid-filled ionization-chamber array (Octavius 1000SRS, PTW, Germany), which has a central resolution of 2.5mm. To test sufficient sensitivity, beam profiles with robot shifts of 0.1mm along the arrays' axes were measured. The detected deviation between the shifted and central profile were compared to the real robot's position. We then compared the results to the SRS-Profiler (SunNuclear, USA) with 4.0mm resolution and to the Nonius (QUART, Germany), a single-line diode detector with 2.8mm resolution. Finally, AQA variance and usability were analyzed performing a number of AQA tests over time, which required the use of specially designed fixtures for each array, and the results were compared to film. Concerning sensitivity, the 1000SRS detected the beam profile shifts with a maximum difference of 0.11mm (mean deviation = 0.03mm) compared to the actual robot shift. The Nonius and SRS-Profiler showed differences of up to 0.15mm and 0.69mm with mean deviation of 0.05mm and 0.18mm, respectively. Analyzing the variation of AQA results over time, the 1000SRS showed a comparable standard deviation to film (0.26mm vs. 0.18mm). The SRS-Profiler and the Nonius showed a standard deviation of 0.16mm and 0.24mm, respectively. The 1000SRS seems to provide equivalent accuracy and sensitivity to the gold standard film when performing daily AQA tests. Compared to other detectors in our study the sensitivity as well as the accuracy of the 1000SRS appears to be superior and more user-friendly. Furthermore, no significant modification of the standard AQA procedure is required when introducing 1000SRS for CyberKnife AQA.

Abstract Background For prostate cancer treatment, treatment options with minimal side effects are desired. External beam radiation therapy (EBRT) is non-invasive, standard of care and delivered in either conventional fractionation over 8 weeks or with moderate hypo-fractionation over about 5 weeks. Recent advances in radiotherapy technology have made extreme hypo-fractionated stereotactic body radiation therapy (SBRT) of prostate cancer feasible, which has not yet been introduced as a standard treatment method in Germany. Initial results from other countries are promising, but long-term results are not yet available. The aim of this study is to investigate feasibility and effectiveness of SBRT for prostate cancer in Germany. Methods/design This German bi-center single group trial (HYPOSTAT) is designed to evaluate feasibility and effectiveness, as measured by toxicity and PSA-response, respectively, of an extreme hypo-fractionated SBRT regimen with five fractions of 7 Gy in treatment of localized low and intermediate risk prostate cancer. The target volume includes the prostate with or without the base of seminal vesicles depending on risk stratification and uncertainty margins that are kept at 3–5 mm. SBRT treatment is delivered with the robotic CyberKnife system, which was recently introduced in Germany. Acute and late toxicity after one year will be evaluated according to Common Terminology Criteria for Adverse Events (CTCAE v. 4.0), Radiation Therapy Oncology Group (RTOG) and International Prostate Symptom Score (IPSS) Scores. The quality of life will be assessed before and after treatment with the EORTC QLQ C30 questionnaire. Hypothesizing that the proportion of patients with grade 2 side effects or higher is less or equal than 2.8%, thus markedly lower than the standard EBRT percentage (17.5%), the recruitment target is 85 patients. Discussion The HYPOSTAT trial aims at demonstrating short term feasibility of extreme hypo-fractioned SBRT for the treatment of prostate cancer and might be used as the pilot study for a multi-center multi-platform or for randomized-controlled trials comparing conventional radiotherapy with SBRT for localized prostate cancer in the future. The study concept of patient enrollment, follow up and evaluation by multiple public university clinics and actual patient treatment in dedicated private radiosurgery practices with high-tech radiation equipment is unique for clinical trials. Study status The study is ongoing and currently recruiting patients. Trial registration Registration number: NCT02635256 ( clinicaltrials.gov ). Registered 8 December 2015.

Abstract Background As irradiated brain volume at 12 Gy (V12) is a predictor for radionecrosis, the purpose of the study was to develop a model for Cyberknife (CK) plans that is able to predict the lowest achievable V12 at a given tumor size and prescription dose (PD), and to suggest a new quality index regarding V12 for optimizing the treatment planning of brain metastases. Method In our model V12 was approximated as a spherical shell around the tumor volume. The radial distance between tumor surface and the 12 Gy isodose line was calculated using an approximation of the mean dose gradient in that area. Assuming a radially symmetrical irradiation from the upper half space, the dose distribution is given by the superposition of single fields. The dose profiles of a single field were derived by the measured off-center ratios (OCR) of the CK system. Using the calculated gradients of the sum dose profiles, minimal-V12 was estimated for different tumor sizes. The model calculation was tested using a phantom dataset and retrospectively applied on clinical cases. Results Our model allows the prediction of a best-case scenario for V12 at a given tumor size and PD which was confirmed by the results of the isocentric phantom plans. The results of the non-isocentric phantom plans showed that an optimization of coverage caused an increase in V12. This was in accordance with the results of the retrospective analysis. V12 s of the clinical cases were on average twice that of the predicted model calculation. A good agreement was achieved for plans with an optimal conformity index (nCI). Re-planning of cases with high V12 showed that lower values could be reached by selecting smaller collimators and by allowing a larger number of total MU and more MU per beam. Conclusions V12 is a main parameter for assessing plan quality in terms of radiotoxicity. The index f12 defined as the ratio of V12 from the actual plan with the evaluated V12 from our model describes the conformity of an optimally possible V12 and thus can be used as a new quality index for optimizing treatment plans.

Introduction: Although stereotactic ablative radiotherapy (SABR) has advance to standard-of-care for many different indications like lung and liver malignancies, it still remains in its infancy for treating head and neck cancer. Nevertheless there is a growing body of experience and evidence, which is summarized in this review Methods A thorough search of the literature was performed and critically reviewed both for SABR as a primary treatment as well as for treating locoregionally recurrent disease in a pre-irradiated field., Results: There exist only few prospective data published so far for treating head and neck cancer with SABR. In the primary situation especially implementing SABR as a boost after definitive radiotherapy or a single-modality for locally limited, small glottic cancer appear promising. On the other hand, SABR can be a useful modality for treating local recurrence in a pre-irradiated field. However, caution is needed in the case of proximity to a pre-irradiated carotid artery or other serial organs at risk. Usually only limited gross volumes are treated with 3-6 fractions every other day and a cumulative dose of 24-44 Gy in dedicated radiosurgery platforms or modern linacs with the possibility of online image-guidance and adequate immobilsation., Conclusions: SABR is an innovative, effective and promising treatment modality for small targets, especially in near proximity to organs at risk or in a pre-irradiated region. Prospective trials are further needed for this technique to become standard-of care., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors. Published by Elsevier B.V. on behalf of European Society for Radiotherapy and Oncology.)

Background: For locally recurrent head and neck cancer, re‐irradiation with modern techniques like stereotactic body radiotherapy is a promising, possibly curative alternative to palliative systemic therapy. Methods: We report on 1 patient with nasopharyngeal carcinoma (NPC) and 1 patient with cutaneous squamous cell carcinoma (SCC). Both patients received full dose primary treatment (>66 Gy, EQD2), full dose re‐irradiation (>50 Gy, EQD2), and a second course of re‐irradiation via robotic radiosurgery (CyberKnife) for a second local recurrence. Results: Both treatments resulted in adequate tumor response. No grade III‐IV acute or late toxicities occurred. Follow‐up at 6 months after third irradiation showed partial remission for the patient with NPC. In the second case (SCC), no toxicities occurred and the tumor was in remission 18 months after last treatment. Conclusion: These cases show that a second course of re‐irradiation utilizing modern techniques like robotic radiosurgery might be feasible for carefully selected patients with head and neck cancer. [ABSTRACT FROM AUTHOR]

Highlights • "Actual and planned target positions were studied preserving reciprocal spatial metric". • "Biphasic breath-hold CT scans are not a good model for planning in 1-view mode". • "The inter-fractional variability cannot be neglected in 1-view treatments". • "The spine-ITV distance variation is a source of localization uncertainty". Abstract Purpose When a lung lesion is detected by only one couple of X-ray tube and image detector integrated with CyberKnife®, the fiducial-less tracking is limited to 1-view (34% of lung treatments at Centro Diagnostico Italiano). The aim of the study was mainly to determine the margin needed to take into account the localization uncertainty along the blind view (out-of-plane direction). Methods 36 patients treated in 2-view tracking modality (127 fractions in total) were included in the study. The actual tumor positions were determined retrospectively through logfile analysis and were projected onto 2D image planes. In the same plots the planned target positions based on biphasic breath-hold CT scans were represented preserving the metric with respect to the imaging center. The internal margin necessary to cover in out-of-plane direction the 95% of the target position distribution in the 95% of cases was calculated by home-made software in Matlab®. A validation test was preliminarily performed using XLT Phantom (CIRS) both in 2-view and 1-view scenarios. Results The validation test proved the reliability of the method, in spite of some intrinsic limitations. Margins were estimated equal to 5 and 6 mm for targets in upper and lower lobe respectively. Biphasic breath-hold CT led to underestimate the target movement in the hypothetical out-of-plane direction. The inter-fractional variability of spine-target distance was an important source of uncertainty for 1-view treatments. Conclusion This graphic comparison method preserving metric could be employed in the clinical workflow of 1-view treatments to get patient-related information for customized margin definition. [ABSTRACT FROM AUTHOR]

Real-time target localization with ultrasound holds high potential for image guidance and motion compensation in radiosurgery due to its non-invasive image acquisition free from ionizing radiation. However, a two-step localization has to be performed when integrating ultrasound into the existing radiosurgery workflow. In addition to target localization inside the ultrasound volume, the probe itself has to be localized in order to transform the target position into treatment room coordinates. By adapting existing camera calibration tools, we have developed a method to extend the stereoscopic X-ray tracking system of a radiosurgery platform in order to locate objects such as marker geometries with six degrees of freedom. The calibration was performed with 0.1 mm reprojection error. By using the full area of the flat-panel detectors without pre-processing the extended software increased the tracking volume and resolution by up to 80%, substantially improving patient localization and marker detectability. Furthermore, marker-tracking showed sub-millimeter accuracy and rotational errors below 0.1°. This demonstrates that the developed extension framework can accurately localize marker geometries using an integrated X-ray system, establishing the link for the integration of real-time ultrasound image guidance into the existing system.

Highlights • Film was used to assess an MC dose calculator for robotic radiosurgery with an MLC. • Within a heterogeneous phantom 91% of pixels pass 2%/1 mm 2D gamma vs. 55% with FSPB. • A calculation limitation was identified and fixed. The gamma pass-rate rose to 97%. • This demonstrates the value of independent validation for any software solution. • The MC algorithm expands the clinical use of robotic radiosurgery with MLC. Abstract Purpose At introduction in 2014, dose calculation for the first MLC on a robotic SRS/SBRT platform was limited to a correction-based Finite-Size Pencil Beam (FSPB) algorithm. We report on the dosimetric accuracy of a novel Monte Carlo (MC) dose calculation algorithm for this MLC, included in the Precision™ treatment planning system. Methods A phantom was built of one slab (5.0 cm) of lung-equivalent material (0.09...0.29 g/cc) enclosed by 3.5 cm (above) and 5 cm (below) slabs of solid water (1.045 g/cc). This was irradiated using rectangular (15.4 × 15.4 mm2 to 53.8 × 53.7 mm2) and two irregular MLC-fields. Radiochromic film (EBT3) was positioned perpendicular to the slabs and parallel to the beam. Calculated dose distributions were compared to film measurements using line scans and 2D gamma analysis. Results Measured and MC calculated percent depth dose curves showed a characteristic dose drop within the low-density region, which was not correctly reproduced by FSPB. Superior average gamma pass rates (2%/1 mm) were found for MC (91.2 ± 1.5%) compared to FSPB (55.4 ± 2.7%). However, MC calculations exhibited localized anomalies at mass density transitions around 0.15 g/cc, which were traced to a simplification in electron transport. Absence of these anomalies was confirmed in a modified build of the MC engine, which increased gamma pass rates to 96.6 ± 1.2%. Conclusions The novel MC algorithm greatly improves dosimetric accuracy in heterogeneous tissue, potentially expanding the clinical use of robotic radiosurgery with MLC. In-depth, independent validation is paramount to identify and reduce the residual uncertainties in any software solution. [ABSTRACT FROM AUTHOR]

Abstract: The Canadian Organization of Medical Physicists (COMP), in close partnership with the Canadian Partnership for Quality Radiotherapy (CPQR) has developed a series of Technical Quality Control (TQC) guidelines for radiation treatment equipment. These guidelines outline the performance objectives that equipment should meet in order to ensure an acceptable level of radiation treatment quality. This particular TQC contains detailed performance objectives and safety criteria for CyberKnife® Technology. The quality control recommendations in this document are based upon previously published guidelines and the collective experience of all Canadian sites using this technology. This TQC guideline has been field tested at the newest Canadian CyberKnife installation site and includes recommendations for quality control of the Iris™ and InCise™ MLC collimation systems. [ABSTRACT FROM AUTHOR]

Background: For prostate cancer treatment, treatment options with minimal side effects are desired. External beam radiation therapy (EBRT) is non-invasive, standard of care and delivered in either conventional fractionation over 8 weeks or with moderate hypo-fractionation over about 5 weeks. Recent advances in radiotherapy technology have made extreme hypo-fractionated stereotactic body radiation therapy (SBRT) of prostate cancer feasible, which has not yet been introduced as a standard treatment method in Germany. Initial results from other countries are promising, but long-term results are not yet available. The aim of this study is to investigate feasibility and effectiveness of SBRT for prostate cancer in Germany.Methods/design: This German bi-center single group trial (HYPOSTAT) is designed to evaluate feasibility and effectiveness, as measured by toxicity and PSA-response, respectively, of an extreme hypo-fractionated SBRT regimen with five fractions of 7 Gy in treatment of localized low and intermediate risk prostate cancer. The target volume includes the prostate with or without the base of seminal vesicles depending on risk stratification and uncertainty margins that are kept at 3-5 mm. SBRT treatment is delivered with the robotic CyberKnife system, which was recently introduced in Germany. Acute and late toxicity after one year will be evaluated according to Common Terminology Criteria for Adverse Events (CTCAE v. 4.0), Radiation Therapy Oncology Group (RTOG) and International Prostate Symptom Score (IPSS) Scores. The quality of life will be assessed before and after treatment with the EORTC QLQ C30 questionnaire. Hypothesizing that the proportion of patients with grade 2 side effects or higher is less or equal than 2.8%, thus markedly lower than the standard EBRT percentage (17.5%), the recruitment target is 85 patients.Discussion: The HYPOSTAT trial aims at demonstrating short term feasibility of extreme hypo-fractioned SBRT for the treatment of prostate cancer and might be used as the pilot study for a multi-center multi-platform or for randomized-controlled trials comparing conventional radiotherapy with SBRT for localized prostate cancer in the future. The study concept of patient enrollment, follow up and evaluation by multiple public university clinics and actual patient treatment in dedicated private radiosurgery practices with high-tech radiation equipment is unique for clinical trials.Study Status: The study is ongoing and currently recruiting patients.Trial Registration: Registration number: NCT02635256 ( clinicaltrials.gov ). Registered 8 December 2015. [ABSTRACT FROM AUTHOR]

Background: As irradiated brain volume at 12 Gy (V12) is a predictor for radionecrosis, the purpose of the study was to develop a model for Cyberknife (CK) plans that is able to predict the lowest achievable V12 at a given tumor size and prescription dose (PD), and to suggest a new quality index regarding V12 for optimizing the treatment planning of brain metastases.Method: In our model V12 was approximated as a spherical shell around the tumor volume. The radial distance between tumor surface and the 12 Gy isodose line was calculated using an approximation of the mean dose gradient in that area. Assuming a radially symmetrical irradiation from the upper half space, the dose distribution is given by the superposition of single fields. The dose profiles of a single field were derived by the measured off-center ratios (OCR) of the CK system. Using the calculated gradients of the sum dose profiles, minimal-V12 was estimated for different tumor sizes. The model calculation was tested using a phantom dataset and retrospectively applied on clinical cases.Results: Our model allows the prediction of a best-case scenario for V12 at a given tumor size and PD which was confirmed by the results of the isocentric phantom plans. The results of the non-isocentric phantom plans showed that an optimization of coverage caused an increase in V12. This was in accordance with the results of the retrospective analysis. V12 s of the clinical cases were on average twice that of the predicted model calculation. A good agreement was achieved for plans with an optimal conformity index (nCI). Re-planning of cases with high V12 showed that lower values could be reached by selecting smaller collimators and by allowing a larger number of total MU and more MU per beam.Conclusions: V12 is a main parameter for assessing plan quality in terms of radiotoxicity. The index f12 defined as the ratio of V12 from the actual plan with the evaluated V12 from our model describes the conformity of an optimally possible V12 and thus can be used as a new quality index for optimizing treatment plans. [ABSTRACT FROM AUTHOR]

Purpose Robotic radiosurgery requires plan delivery quality assurance (DQA) but there has never been a published comprehensive analysis of a patient-specific DQA process in a clinic. We proposed to evaluate 350 consecutive film-based patient-specific DQAs using statistical process control. We evaluated the performance of the process to propose achievable tolerance criteria for DQA validation and we sought to identify suboptimal DQA using control charts. Methods and material DQAs were performed on a CyberKnife-M6 using Gafchromic-EBT3 films. The signal-to-dose conversion was performed using a multichannel-correction and a scanning protocol that combined measurement and calibration in a single scan. The DQA analysis comprised a gamma-index analysis at 3%/1.5 mm and a separate evaluation of spatial and dosimetric accuracy of the plan delivery. Each parameter was plotted on a control chart and control limits were calculated. A capability index (Cpm) was calculated to evaluate the ability of the process to produce results within specifications. Results The analysis of capability showed that a gamma pass rate of 85% at 3%/1.5 mm was highly achievable as acceptance criteria for DQA validation using a film-based protocol (Cpm > 1.33). 3.4% of DQA were outside a control limit of 88% for gamma pass-rate. The analysis of the out-of-control DQA helped identify a dosimetric error in our institute for a specific treatment type. Conclusion We have defined initial tolerance criteria for DQA validations. We have shown that the implementation of a film-based patient-specific DQA protocol with the use of control charts is an effective method to improve patient treatment safety on CyberKnife. [ABSTRACT FROM AUTHOR]

Aim This study evaluates the toxicity and outcome in patients treated with robotic radiosurgery for liver metastases. Background Modern technologies allow the delivery of high doses to the liver metastases while lowering the dose to the neighboring organs at risk. Whether this dosimetric advantage translates into clinical benefit is not well known yet. Methods and materials A total of 9 patients with 17 liver metastases have been treated with robotic stereotactic body radiotherapy SBRT from March 2011 to December 2014. Local response to SBRT was graded by the Response Evaluation Criteria in Solid Tumors criteria to describe change in treated tumor lesion. Adverse events after SBRT were graded on a 1–5 scale according to the National Cancer Institute common terminology criteria for adverse events v4.0. Results Patients received either three (78%) or five (22%) fractions. Patients were treated with a mean fraction dose of 14 Gy with a range from 9 to 20 Gy. The median total radiation dose provided to patients was 45 Gy with a range of 45–60 Gy. Four out of the 17 (23.5%) treated lesions had a complete response, 9 (53%) partial response and 3 (17.6%) stable disease. With a median follow-up of 15.2 months after SBRT treatment, local control and overall survival rated were 89% and 66%, respectively. No patient experienced grade ≥3 toxicity. The most common toxicity reported was asthenia. Only two patients had nausea and diarrhea, 10 and 14 days after SBRT, respectively. Conclusions Robotic radiosurgery is a safe and effective local treatment option for secondary liver tumors. Further prospective studies are ongoing to determine long-term response and survival after robotic-SBRT for liver metastases. [ABSTRACT FROM AUTHOR]