CyberKnife Robotic Radiosurgery System Research Articles

Long-term clinical outcomes of hypofractionated stereotactic radiotherapy using the CyberKnife robotic radiosurgery system for jugular foramen schwannomas.

Jugular foramen schwannomas (JFSs) are rarely seen, benign tumors with slow growth. Today, management options for JFSs include observation, surgery, and radiation. However, the optimal treatment strategy remains controversial. Stereotactic radiosurgery serves as a minimally invasive alternative or adjuvant therapeutic regimen of microsurgery. Gamma Knife radiosurgery is suitable for patients with JFS who have small- and medium-sized tumors and normal cranial nerve (CN) function. Hypofractionated stereotactic radiotherapy (HSRT) offers a potential radiobiological advantage and may result in better preservation of normal structures compared to single-fraction stereotactic radiosurgery. The aim of the article was to review the clinical and radiographic outcomes of patients with JFS who were treated using HSRT. The authors retrospectively analyzed 74 patients with JFS who received HSRT between January 2009 and January 2020 in the authors' center. Among them, 53 patients were newly diagnosed with JFS, 19 patients had a previous history of microsurgical resection, and the other 2 patients underwent CyberKnife because of tumor recurrence after Gamma Knife radiosurgery. A total of 73 patients had preexisting CN symptoms and signs. The median tumor volume was 14.8 cm3 (range 0.5-41.2 cm3), and most of them (70.3%) were ≥ 10 cm3. The radiation dose regimen was prescribed depending on the tumor size, and more fractions were used in larger tumors. The median margin doses prescribed were 18.2 Gy/2 fractions, 21.0 Gy/3 fractions, and 21.6 Gy/4 fractions. The median follow-up was 103 months (range 18-158 months). After treatment, 42 (56.8%) patients had tumor regression, 27 (36.5%) patients had stable tumors, and 5 (6.8%) experienced tumor progression. Among them, MRI revealed that 1 patient had a complete response. Three patients received surgery at a median of 25 months because of tumor progression. One patient underwent ventriculoperitoneal shunt insertion for hydrocephalus that developed after HSRT independent of tumor progression. The 5-year progression-free survival rate was 93.2%. Preexisting cranial neuropathies improved in 46 patients, remained stable in 14, and worsened in 14. HSRT proved to be a safe and effective primary or adjuvant treatment strategy for JFSs, although 14 patients (18.9%) experienced some degree of delayed symptomatic deterioration posttreatment. This therapeutic option was demonstrated to provide both excellent tumor control and improvement in CN function.

Re-irradiation with stereotactic radiotherapy for recurrent high-grade glial tumors.

Despite the radical treatments applied, recurrence is encountered in the majority of high-grade gliomas (HGG). There is no standard treatment when recurrence is detected, but stereotactic radiotherapy (SRT) is a preferable alternative. The aim of this retrospective study is to evaluate the efficacy of SRT for recurrent HGG, and to investigate the factors that affect survival. From 2013 to 2021, a total of 59 patients with 64 lesions were re-irradiated in a single center with the CyberKnife Robotic Radiosurgery System. The primary endpoints of the study were overall survival (OS), progression free survival (PFS) and local control rates (LCR). The median time to first recurrence was 13 (4-85) months. SRT was performed as a median prescription dose of 30 Gy (range 15-30), with a median of 5 fractions (1-5). The median follow-up time was 4 months (range 1-57). The median OS was 8 (95% CI: 4.66-11.33) months. Age, grade 3, tumor size were associated with better survival. The median PFS was 5 [95% confidence interval (CI): 3.39-6.60] months. Age, grade 3 and time to recurrence > 9 months were associated with improved PFS. Grade 3 gliomas (p = 0.027), size of tumor < 2 cm (p = 0.008) remained independent prognostic factors for OS in multivariate analysis. SRT is a viable treatment modality with significant survival contribution. Since it may have a favorable prognostic effect on survival in patients with tumor size < 2 cm, we recommend early diagnosis of recurrence and a decision to re-irradiate a smaller tumor during follow-up.

Small field output factor measurement and verification for CyberKnife robotic radiotherapy and radiosurgery system using 3D polymer gel, ionization chamber, diode, diamond and scintillator detectors, Gafchromic film and Monte Carlo simulation

The dosimetry of small fields has become tremendously important with the advent of intensity-modulated radiation therapy (IMRT) and stereotactic radiosurgery, where small field segments or very small fields are used to treat tumors. With high dose gradients in the stereotactic radiosurgery or radiotherapy treatment, small field dosimetry becomes challenging due to the lack of lateral electronic equilibrium in the field, x-ray source occlusion, and detector volume averaging. Small volume and tissue-equivalent detectors are recommended to overcome the challenges. With the lack of a perfect radiation detector, studies on available detectors are ongoing with reasonable disagreement and uncertainties. The joint IAEA and AAPM international code of practice (CoP) for small field dosimetry, TRS 483 (Alfonso et al., 2017) provides guidelines and recommendations for the dosimetry of small static fields in external beam radiotherapy. The CoP provides a methodology for field output factor (FOF) measurements and use of field output correction factors for a series of small field detectors and strongly recommends additional measurements, data collection and verification for CyberKnife (CK) robotic stereotactic radiotherapy/radiosurgery system using the listed detectors and more new detectors so that the FOFs can be implemented clinically. The present investigation is focused on using 3D gel along with some other commercially available detectors for the measurement and verification of field output factors (FOFs) for the small fields available in the CK system. The FOF verification was performed through a comparison with published data and Monte Carlo simulation. The results of this study have proved the suitability of an in-house developed 3D polymer gel dosimeter, several commercially available detectors, and Gafchromic films as a part of small field dosimetric measurements for the CK system.

Evaluation of calibration methods of Exradin W2 plastic scintillation detector for CyberKnife small-field dosimetry

PurposePlastic scintillation detectors (PSD) require corrections of Cerenkov light for accurate radiation dosimetry. The vendor-recommended calibration method of the Exradin W1 requires irradiation with a 40 × 40 cm2 field size, although the CyberKnife robotic radiosurgery system cannot generate such large field. Recently, an Exradin W2 PSD, succeeding Exradin W1, was characterized. The W2 PSD can be calibrated in water with small curvature using a new plastic holder, which has a short pole on the bottom to mount it on the arm of the water phantom. The purpose of this study was to evaluate the calibration method of Exradin W2 using the new plastic holder for calibration with small fields and compare the impact of the calibration methods on the beam data. MethodsAn Exradin W2-1x1 detector with active volume length 1 mm and diameter 1 mm was used. The Cerenkov light ratio (CLR) values were determined by two calibration methods: measurements in a 30 × 30 cm2 solid water and in water using a small plastic holder. Percent-depth-dose (PDD), beam profiles, and detector output factor (OFdet) of TrueBeam 6 MV photon beams with flattening filter (WFF) and flattening filter-free (FFF) beams were measured to compare these two calibration methods. For the CyberKnife photon beams, PDD, beam profiles, and OFdet were measured with the calibration in water, and the data were compared with those measured using a Diode SRS (PTW model 60018) and microDiamond (PTW model 60019). ResultsThe difference of the CLR between two calibration methods were within 3%. The effect of the calibration methods on the PDD, beam profiles, and OFdet of the TrueBeam were within 0.06%, 0.07%, and 0.8%, respectively. For the CyberKnife beams, the maximum difference of PDD in the dose fall-off region, full-width half-maximum (FWHM) of beam profiles, and penumbra among the three detectors were 1.3%, 0.25 mm, and 0.35 mm, respectively. The relative difference of the W2-measured OFdet from the microDiamond-measured field output factor were within 1.7%. ConclusionsThe calibration in water with a small-field size provided equivalent data compared to those obtained with a conventional calibration method. The Exradin W2 provided appropriate data for CyberKnife small-field dosimetry.

Dosimetric comparison of Synchrony® real-time motion tracking treatment plans between CyberKnife robotic radiosurgery and Radixact system for stereotactic body radiation therapy of lung and prostate cancer

Abstract The aim of this study was to assess which machine, Radixact or CyberKnife, can deliver better treatment for lung and prostate stereotactic body radiation therapy (SBRT) with the use of Synchrony® real-time motion tracking system. Ten and eight patients treated with lung and prostate SBRT, respectively, using the CyberKnife system were selected for the assessment. For each patient, a retrospective Radixact plan was created and compared with the original CyberKnife plan. There was no statistically significant difference in the new conformity index of the Radixact plans and that of the Cyberknife plans in both lung and prostate SBRT. The average homogeneity index in the Radixact plans was better in both lung and prostate SBRT with statistical significance (p = 0·04 for lung and p = 0·02 for prostate). In lung SBRT, the dose to lungs was lower in Cyberknife plans (p = 0·002). In prostate SBRT, there was no statistically significant difference in organs at risk sparing between Cyberknife plans and Radixact plans. In conclusion, CyberKnife was better in lung SBRT while Radixact was better in prostate SBRT.

Small Field Output Factor Measurement and Verification for Cyberknife Robotic Radiotherapy and Radiosurgery System Using 3D Polymer Gel, Ionization Chamber, Diode, Diamond and Scintillator Detectors, Gafchromic Film and Monte Carlo Simulation

Small Field Output Factor Measurement and Verification for Cyberknife Robotic Radiotherapy and Radiosurgery System Using 3D Polymer Gel, Ionization Chamber, Diode, Diamond and Scintillator Detectors, Gafchromic Film and Monte Carlo Simulation

Development of a tracking error prediction system for the CyberKnife Synchrony Respiratory Tracking System with use of support vector regression.

The accuracy of the CyberKnife Synchrony Respiratory Tracking System is dependent on the breathing pattern of a patient. Therefore, the tracking error in each patient must be determined. Support vector regression (SVR) can be used to easily identify the tracking error in each patient. This study aimed to develop a system with SVR that can predict tracking error according to a patient's respiratory waveform. Datasets of the respiratory waveforms of 93 patients were obtained. The feature variables were variation in respiration amplitude, tumor velocity, and phase shift between tumor and the chest wall, and the target variable was tracking error. A learning model was evaluated with tenfold cross-validation. We documented the difference between the predicted and actual tracking errors and assessed the correlation coefficient and coefficient of determination. The average difference and maximum difference between the actual and predicted tracking errors were 0.57 ± 0.63 mm and 2.1 mm, respectively. The correlation coefficient and coefficient of determination were 0.86 and 0.74, respectively. We developed a system for obtaining tracking error by using SVR. The accuracy of such a system is clinically useful. Moreover, the system can easily evaluate tracking error. We developed a system that can be used to predict the tracking error of SRTS in the CyberKnife Robotic Radiosurgery System using machine learning. The feature variables were the breathing parameters, and the target variable was the tracking error. We used support vector regression algorithm.

Cosmetic Outcomes of a Phase 1 Dose Escalation Study of 5-Fraction Stereotactic Partial Breast Irradiation for Early Stage Breast Cancer

Our purpose was to evaluate cosmetic changes after 5-fraction adjuvant stereotactic partial breast irradiation (S-PBI). Seventy-five women with in situ or invasive breast cancer stage 0, I, or II, with tumor size ≤3 cm, were enrolled after lumpectomy in a phase 1 dose escalation trial of S-PBI into cohorts receiving 30, 32.5, 35, 37.5, or 40 Gy in 5 fractions. Before S-PBI, 3 to 4 gold fiducial markers were placed in the lumpectomy cavity for tracking with the Synchrony respiratory tracking system. S-PBI was delivered with a CyberKnife robotic radiosurgery system. Patients and physicians evaluated global cosmesis using the Harvard Breast Cosmesis Scale. Eight independent panelists evaluated digital photography for global cosmesis and 10 subdomains at baseline and follow-up. McNemar tests were used to evaluate change in cosmesis, graded as excellent/good or fair/poor, from baseline to year 3. Wilcoxon signed rank tests were used to evaluate change in subdomains. Cohen's kappa (κ) statistic was used to estimate interobserver agreement (IOA) between raters, and Fleiss' κ was used to estimate IOA between panelists. Median cosmetic follow-up was 5, 5, 5, 4, and 3 years for the 30, 32.5, 35, 37.5, and 40 Gy cohorts. Most patients reported excellent/good cosmesis at both baseline (86.3%) and year 3 (89.8%). No dose cohort had significantly worsened cosmesis by year 3 on McNemar analysis. No cosmetic subdomain had significant worsening by year 3. IOA was fair for patient-physician (κ = 0.300, P < .001), patient-panel (κ = 0.295, P < .001), physician-panel (κ = 0.256, P < .001), and individual panelists (Fleiss κ = 0.327, P < .001). Dose escalation of S-PBI from 30 to 40 Gy in 5 fractions for early stage breast cancer was not associated with a detectable change in cosmesis by year 3. S-PBI is a promising modality for treatment of early stage breast cancer.

Output factor measurements with multiple detectors in CyberKnife® Robotic Radiosurgery System.

The aim of this study was to measure and compare the output factor (OF) of a CyberKnife Robotic Radiosurgery System with eight different small field detectors and validate with Technical Report Series (TRS) report 483. Accurate dosimetry of CyberKnife system is limited due to the challenges in small field dosimetry. OF is a vital dosimetric parameter used in the photon beam modeling and any error would affect the dose calculation accuracy. In this study, the OF was measured with eight different small-field detectors for the 12 IRIS collimators at 800 mm SAD setup at 15 mm depth. The detectors used were PTW 31016 PinPoint 3D, IBA PFD shielded diode, IBA EFD unshielded diode, IBA SFD unshielded diode (stereotactic), PTW 60008 shielded diode, PTW 60012 unshielded diode, PTW 60018 unshielded diode (stereotactic), and PTW 60019 CVD diamond detector. OF was obtained after correcting for field output correction factors from IAEA TRS No. 483. The field OFs in CyberKnife are derived from the measured data by applying the correction factors from Table 23 in TRS 483 for the eight small field detectors. These field OFs matched within 2% of peer-reviewed published values. The range and standard deviation showed a decreasing trend with collimator diameter. The field OF obtained after applying the appropriate correction factor from TRS 483 matched well with the peer-reviewed published OFs. The inter-detector variation showed a decreasing trend with increasing collimator field size. This study gives physicists confidence in measuring field OFs while using small field detectors mentioned in this work.

Commissioning and clinical implementation of the first commercial independent Monte Carlo 3D dose calculation to replace CyberKnife M6™ patient-specific QA measurements.

PurposeTo report on the commissioning and clinical validation of the first commercially available independent Monte Carlo (MC) three‐dimensional (3D) dose calculation for CyberKnife robotic radiosurgery system® (Accuray, Sunnyvale, CA).MethodsThe independent dose calculation (IDC) by SciMoCa® (Scientific RT, Munich, Germany) was validated based on water measurements of output factors and dose profiles (unshielded diode, field‐size dependent corrections). A set of 84 patient‐specific quality assurance (QA) measurements for multi‐leaf collimator (MLC) plans, using an Octavius two‐dimensional SRS1000 array (PTW, Freiburg, Germany), was compared to results of respective calculations. Statistical process control (SPC) was used to detect plans outside action levels.ResultsOf all output factors for the three collimator systems of the CyberKnife, 99% agreed within 2% and 81% within 1%, with a maximum deviation of 3.2% for a 5‐mm fixed cone. The profiles were compared using a one‐dimensional gamma evaluation with 2% dose difference and 0.5 mm distance‐to‐agreement (Γ(2,0.5)). The off‐centre ratios showed an average pass rate >99% (92–100%). The agreement of the depth dose profiles depended on field size, with lowest pass rates for the smallest MLC field sizes. The average depth dose pass rate was 88% (35–99%). The IDCs showed a Γ(2,1) pass rate of 98%. Statistical process control detected six plans outside tolerance levels in the measurements, all of which could be attributed the measurement setup. Independent dose calculations showed problems in five plans, all due to differences in the algorithm between TPS and IDC. Based on these results changes were made in the class solution for treatment plans.ConclusionThe first commercially available MC 3D dose IDC was successfully commissioned and validated for the CyberKnife and replaced all routine patient‐specific QA measurements in our clinic.

Improving stereotactic radiotherapy (SRT) planning process for brain metastases by Cyberknife system: reducing dose distribution in healthy tissues.

Purpose: To pursue high precision dose in lesions and steeper dose fall-off in healthy tissues of brain metastases stereotactic radiotherapy (SRT), this study investigated an opitimized planning by comparison different prescription dose line in the treatment of brain metastases using Cyberknife (CK) Robotic Radiosurgery System.Methods: 77 patients (92 lesions) brain metastases patients CK SRT plans were replanned with 50%-80% (5% internal) prescription dose line to cover more than 95% of the planned target volume (PTV), under the same collimator by Multiplan System. Under the precondition of guaranteeing plans all meet the clinical requirements, the plan evaluation paraments (conformal index (CI) and homogeneity index (HI)), plan treatment time parameters (the total number of beams and monitor units (MU)) and dose distribution of organs at risk (OAR) and healthy brain tissues adjacent to the PTV were analyzed respectively.Resluts: Compared with 70% plans, 65% plans had: 1) average dose (Dmean) and maximum dose (Dmax) of healthy brain tissue outside of the PTV reduced 11.83% and 5.97% markedly; 2) Dmean and Dmax of brainstem decreased 11.43% and 2.86%; 3) the volumes of whole brain minus the tumors received a single dose equivalence of 12 Gy/14 Gy (V12Gy/V14Gy) had marked decline. The dose fall-off was considerably faster in the 60%-65% plans around the PTV and the maximum dose of healthy tissue was prominently lower. While the difference in CI and HI between different plans was not obvious, the plan treatment time was a little higher in 60%-65% plans than 70%-80% plans.Conclusions: Choosing a relatively lower isodose as the prescription dose line for brain metastases CK SRT planing could improve the dosimetry index of target and immensely reduce high dose in healthy brain tissue and OAR.

Plan Quality and Secondary Cancer Risk Assessment in Patients with Benign Intracranial Lesions after Radiosurgery using the CyberKnife M6 Robotic Radiosurgery System

This study was performed to examine the quality of planning and treatment modality using a CyberKnife (CK) robotic radiosurgery system with multileaf collimator (MLC)-based plans and IRIS (variable aperture collimator system)-based plans in relation to the dose–response of secondary cancer risk (SCR) in patients with benign intracranial tumors. The study population consisted of 15 patients with benign intracranial lesions after curative treatment using a CyberKnife M6 robotic radiosurgery system. Each patient had a single tumor with a median volume of 6.43 cm3 (range, 0.33–29.72 cm3). The IRIS-based plan quality and MLC-based plan quality were evaluated by comparing the dosimetric indices, taking into account the planning target volume (PTV) coverage, the conformity index (CI), and the dose gradient (R10% and R50%). The dose–response SCR with sarcoma/carcinoma induction was calculated using the concept of the organ equivalent dose (OED). Analyses of sarcoma/carcinoma induction were performed using excess absolute risk (EAR) and various OED models of dose–response type/lifetime attributable risk (LAR). Moreover, analyses were performed using the BEIR VII model. PTV coverage using both IRIS-based plans and MLC-based plans was identical, although the CI values obtained using the MLC-based plans showed greater statistical significance. In comparison with the IRIS-based plans, the MLC-based plans showed better dose falloff for R10% and R50% evaluation. The estimated difference between Schneider’s model and BEIR VII in linear-no-threshold (Lnt) cumulative EAR was about twofold. The average values of LAR/EAR for carcinoma, for the IRIS-based plans, were 25% higher than those for the MLC-based plans using four SCR models; for sarcoma, they were 15% better in Schneider’s SCR models. MLC-based plans showed slightly better conformity, dose gradients, and SCR reduction. There was a slight increase in SCR with IRIS-based plans in comparison with MLC-based plans. EAR analyses did not show any significant difference between PTV and brainstem analyses, regardless of the tumor volume. Nevertheless, an increase in target volume led to an increase in the probability of SCR. EAR showed statistically significant differences in the soft tissue according to tumor volume (1–10 cc and ≥10 cc).

Dose analysis of InCise 2 multi leaf collimator and IRIS-based stereotactic radiotherapy plans for brain and liver tumors

Second-generation multi leaf collimator (MLC) has been introduced for the CyberKnife Robotic Radiosurgery System (Accuray Inc., Sunnyvale, USA) in 2016. The aim of the present study was to compare the plan quality between InCise 2 MLC and IRIS by analyzing dose parameters for small and large targets such as brain metastases and liver tumors, respectively. Ten brain metastases targets and 10 liver targets were selected. The following parameters were analyzed: coverage, dose distributions in planning target volume (PTV) and organs at risk (OAR), conformity index (CI), Nakamura CI (nCI), homogeneity index (HI), gradient index (GI), V12 Gy within brain, treatment time, number of beams, nodes and monitor units (MU). For brain patient group, CI and nCI were lower with IRIS plans (1.18 versus 1.26; p = 0.048 and 1.19 versus 1.28; p = 0.033, respectively), whereas GI values were higher in InCise 2 MLC plans (0.36 versus 0.33; p < 0.01). PTV mean doses were higher with IRIS plans (1.13 versus 1.16; p = 0.03). For liver tumors, InCise 2 MLC plans reached higher GI values (0.32 versus 0.29; p < 0.01). PTV minimum and mean doses were higher with IRIS plans (0.85 versus 0.93; p < 0.01 and 1.17 versus 1.2; p = 0.046, respectively). OAR’s mean dose for bowel, left-right kidney and healthy liver tissue were lower with MLC plans (0.02 versus 0.04, 0.02 versus 0.05, 0.07 versus 0.10, and 0.20 versus 0.21; p < 0.01, respectively). Shorter delivery time was reached with InCise 2 MLC for both groups (38 versus 56 min, and 42 versus 56 min; p < 0.01, for brain and liver, respectively). Results of this study showed that second generation MLC plans for intracranial and liver targets were dosimetrically feasible. The main advantages of InCise 2 MLC are the improved dose gradient and delivery time.

Stereotactic body radiation therapy for clinically localized prostate cancer

Background. In the last decade, we observed a significant increase in the number of patients undergoing radiotherapy for prostate cancer (PC). It became possible with the development of new equipment that can significantly increase radiation efficiency and reduce the frequency and severity of side effects. Active investigation of new fractionation regimens led to the development of stereotactic radiotherapy (StR) technique. In this article, we describe our own experience of using StR in patients with localized PC.Material and methods. The study included 48 patients treated with CyberKnife robotic radiosurgery system. The patients received a total dose of 36.25 Gy delivered in 5 fractions.Results. At a median follow-up of 24 months, the estimated four-year prostate-specific antigen (PSA) relapse-free survival rate was 95.8 %. The median PSA nadir was 0.48 ng/mL. We observed no grade III–IV side effects (either early or late).Conclusion. Our results suggest that the use of StR allows achieving good biochemical control comparable to that achieved by other methods and demonstrates comparable and sometimes even lower toxicity.

Do SABR-related toxicities for lung cancer depend on treatment delivery?

Stereotactic ablative radiation therapy for lung cancer is an advanced technique where tumours are ablated with hypofractionated radiation doses, with a high degree of accuracy. The aim of this paper is to review the available literature and to discuss the SABR-induced toxicities for lung malignancies as a function of radiation delivery technique. A Medline search was conducted to identify the appropriate literature to fulfil the aim of this review and data from all applicable papers were collated and analysed. The most common techniques of SABR delivery employ linear accelerators, CyberKnife robotic radiosurgery system, TomoTherapy and the Novalis beam surgery system. Linear accelerator-based treatments give rise to a variety of toxicities that are strongly dependent on both patient-related factors and planning/dosimetry-related factors. The limited number of studies using CyberKnife reported low grade toxicities. Grade three toxicities mainly include fatigue and chest pain, usually in less than 10% of patients. All treatment techniques presented show efficiency in SABR delivery with various toxicities which, at this stage, cannot render one technique better than the other. For more conclusive results, well-designed phase three randomised clinical trials are required with better patient selection criteria, including dose and fractionation, treatment machine and technique, along with the consistent selection of a common toxicity grading criterion.

Participating in an International Stereotactic Radiotherapy Patient Registry: The Establishment of Data Collection Pathways.

AimTo describe data collection pathways and practical challenges experienced by an academic comprehensive cancer centre aiming to record clinical data for patients being treated with a novel radiotherapy treatment modality.MethodsVarious options to capture data from all patients treated with the CyberKnife Robotic Radiosurgery System at Sir Charles Gairdner Hospital (SCGH) in Western Australia were explored. An international multicenter web-based secure database established and maintained by the Radiosurgery Society the RSSearch® Patient Registry was selected. Data were collected and entered over four contiguous phases, with either opt-in or opt-out consent and the completion of Patient Reported Outcome questionnaires for specific sub-groups.ResultsBetween April 2014 and June 2016, 461 patients at Sir Charles Gairdner Hospital were enrolled in the RSSearch® Patient Registry with the collection of over 17,500 data items. From 461 patients enrolled, 447 patients were treated with the CyberKnife Robotic Radiosurgery System. The majority of patients were treated for either a malignant primary (43.2%) or metastatic disease (39.4%). The establishment of matrix organisational processes for data collection led to the development of improved workflow patterns and data collection pathways.ConclusionsThis article describes the processes developed by a single centre to establish an efficient system for data collection and participation in an international registry. The opt-out approach was more efficient in terms of patient recruitment compared to the informed-consent method used in earlier phases. The experience of this single centre may help inform other institutions considering data collection options for assessments of new or novel treatments.

Integration of Functional MRI and White Matter Tractography in CyberKnife Radiosurgery.

Purpose:To investigate the efficacy of the integration of functional magnetic resonance imaging and diffusion-tensor imaging tractography data into CyberKnife radiosurgery for intracranial tumor management.Materials and Methods:Functional neuroimaging, anatomical magnetic resonance imaging, and computed tomography images of patients with brain lesions in critical areas were acquired before radiosurgery. The acquired data sets were coregistered using the MIM image fusion software module and then were imported into the CyberKnife Robotic Radiosurgery System (Multiplan 4.0.2) for delineating the target, organs at risk, and possible nearby functionally relevant cortical and subcortical areas. Radiation dose distributions with and without the functionally relevant cortical and subcortical areas into the optimization process were developed and compared.Results:There were significant differences between the treatment plans with and without the functionally relevant cortical and subcortical areas into the optimization process. An average 22.71% reduction in the maximum dose to functional areas was observed. No neurological complication due to radiation damage was observed in the follow-up period.Conclusion:The functional neuroimaging could be easily and reliably integrated into the CyberKnife treatment planning. Consideration of functional structures and fiber tracts during treatment planning could clinically reduce the radiation doses to these critical structures, thereby preserving its unique function of brain.

A Dose-Volume Response Model for Brain Metastases Treated With Frameless Single-Fraction Robotic Radiosurgery: Seeking to Better Predict Response to Treatment.

Purpose/Objective(s):To establish a dose–volume response relationship for brain metastases treated with single-fraction robotic stereotactic radiosurgery and identify predictors of local control.Materials/Methods:We reviewed a prospective institutional database of all patients treated for intact brain metastases with stereotactic radiosurgery alone using the CyberKnife robotic radiosurgery system from 2012 to 2015. Tumor response was determined based on Response Evaluation Criteria In Solid Tumors version 1.1. Survival was estimated using the Kaplan-Meier method. Logistic regression modeling was used to identify predictors of outcome and establish a dose–volume response relationship. Receiver operating characteristic curves were constructed to evaluate the predictive capability of the relationship.Results:There were 357 metastases evaluated in 111 patients with a median diameter of 8.14 mm (2.00-40.77 mm). At 6 and 12 months, local control was 86.9% and 82.2%, respectively. For lesions of similar volumes, higher maximum dose, mean dose, and minimum dose (all P values <.05) predicted for better local control. Tumor volume and diameter were strongly correlated, and a dose–volume response relationship was constructed using mean dose per lesion diameter (Gy/mm) that was predictive of local control (odds ratio: 1.34, 95% confidence interval: 1.06-1.70). Area under the receiver operating characteristic curve for local control and mean dose by volume was 0.6199 with a threshold of 2.05 Gy/mm (local failure 7.6% above and 17.3% below 2.05 Gy/mm).Conclusion:A dose–volume response relationship exists for brain metastases treated with robotic stereotactic radiosurgery. Mean dose per volume is strongly predictive of local control and can be potentially useful during stereotactic radiosurgery plan evaluation while respecting previously established dose constraints.

Motion compensation for robotic lung tumour radiotherapy in remote locations: A personalised medicine approach

The purpose of this work is to integrate the concept of patient-in-the-closed-loop application with tumour treatment of cancer-diagnosed patients in remote areas. The generic closed loop control objective is effective synchronisation of the radiation focus to the movement of a lung tissue tumour during actual breathing of the patient. This is facilitated by accurate repositioning of a robotic arm manipulator, i.e. we emulate the Cyberknife Robotic Radiosurgery system. Predictive control with disturbance filter is used in this application in a minimalistic model design. Performance of the control structure is validated by means of simulation using real recorded breathing patterns from patients measured in 3D space. Latency in communication protocol is taken into account, given telerobotics involve autonomous operation of a robot interacting with a human being in different location. Our results suggest that the proposed closed loop control structure has practical potential to individualise the treatment and improves accuracy by at least 15%.

Target delineation and optimal radiosurgical dose for pituitary tumors.

Stereotactic radiosurgery (SRS) delivered as either single-fraction or multi-fraction SRS (2–5 fractions) is frequently employed in patients with residual or recurrent pituitary adenoma. The most common delivery systems used for SRS include the cobalt-60 system Gamma Knife, the CyberKnife (CK) robotic radiosurgery system, or a modified conventional radiotherapy machine (linear accelerator, LINAC). Tumor control and normalization of hormone hypersecretion have been reported in 75–100 % and 25–80 % of patients, respectively. Hypopituitarism is the most commonly reported late complication of radiation treatment, whereas other toxicities occur less frequently. We have provided an overview of the recent available literature on SRS in patients with a pituitary adenoma. Critical aspects of pituitary irradiation, including target delineation and doses to organs at risk, optimal radiation dose, as well as the long-term efficacy and toxicity of SRS for either nonfunctioning or secreting pituitary adenomas are discussed. Single-fraction SRS represents an effective treatment for patients with a pituitary adenoma; however, caution should be used for lesions > 2.5–3 cm in size and/or involving the anterior optic pathway. Future studies will be necessary to optimize target doses and critical organ dose constrains in order to reduce the long-term toxicity of treatments while maintaining high efficacy.