Field Of Stereotactic Radiosurgery Research Articles

Trends in Stereotactic Radiosurgery for Intracranial and Spinal Pathologies: Analysis of the Top 100 Most Cited Articles.

There is a plethora of papers on the role of stereotactic radiosurgery (SRS) in various benign and malignant intracranial tumors, and it is possible to overlook the most important and landmark studies. Thus, the necessity of citation analysis arises, which reviews the most cited articles and recognizes the impact made by these articles. Utilizing the 100 most cited articles describing the use of SRS for intracranial and spinal pathologies, this article aims to provide meaningful information regarding the historical trends and recent directions in which this field is headed. We performed a search of the Web of Science database using the keywords "stereotactic radiosurgery," "gamma knife," "GKRS," "gamma knife radiosurgery," "LINAC," and "Cyberknife" on May 14, 2022. Our search retrieved a total of 30,652 articles published between the years 1968 and 2017. The top 100 cited articles were arranged in descending order based on citation count (CC) and citation per year (CY). The journal with the largest number of publications as well as citation count was the International Journal of Radiation Oncology Biology Physics (n = 33), followed by Journal of Neurosurgery (n = 25). The most cited article was authored by Andrews, which was published in 2004 in The Lancet (1699 CC, 89.42 CY). Flickinger, with 25 papers and 7635 total citations, was the author with the highest impact. Lunsford, with 25 publications and total citations of 7615, was a close second. The USA was the leading country with the maximum number of total citations (n = 23,054). Ninety-two articles described the use of SRS for intracranial pathologies (metastases, n = 38; AVM, n = 16; vestibular schwannoma, n = 9; meningioma, n = 8; trigeminal neuralgia, n = 6; sellar lesion, n = 2; glioma, n = 2; functional, n = 1; and procedure related, n = 10). Eight studies describing spinal radiosurgery were included, out of which four were on spinal metastases. Citation analyses of the top 100 articles revealed that the focus of research in the field of SRS started with functional neurosurgery and progressed to benign intracranial tumors and AVMs. More recently, central nervous system (CNS) metastases have received the maximum attention with 38 articles, including 14 randomized controlled trials finding a place in the top 100 cited articles. Presently, the use of SRS is concentrated in developed countries. Efforts need to be made for more widespread use in developing nations to bring the maximum possible benefits of this focused noninvasive treatment to a wider population.

Historical Progress of Stereotactic Radiation Surgery.

Radiosurgery and stereotactic radiotherapy have established themselves as precise and accurate areas of radiation oncology for the treatment of brain and extracranial lesions. Along with the evolution of other methods of radiotherapy, this type of treatment has been associated with significant advances in terms of a variety of modalities and techniques to improve the accuracy and efficacy of treatment. This paper provides a comprehensive overview of the progress in stereotactic radiosurgery (SRS) over several decades, and includes a review of various articles and research papers, commencing with the emergence of stereotactic techniques in radiotherapy. Key clinical aspects of SRS, such as fixation methods, radiobiology considerations, quality assurance practices, and treatment planning strategies, are presented. In addition, the review highlights the technological advancements in treatment modalities, encompassing the transition from cobalt-based systems to linear accelerator-based modalities. By addressing these topics, this study aims to offer insights into the advancements that have shaped the field of SRS, that have ultimately enhanced the accuracy and effectiveness of treatment.

Self-Shielding Gyroscopic Radiosurgery—A First Clinical Experience, Case Series, and Dosimetric Comparison

Self-shielding gyroscopic radiosurgery (GRS) represents a technical innovation in the field of stereotactic radiosurgery. GRS does not require a radiation vault and is optimized for radiosurgical treatments. Reports on its usage are limited. We describe the first clinical experience of GRS at our institution to assess the application of GRS in the treatment of cranial tumors. Moreover, we perform a dosimetric comparison to robotic radiosurgery (RRS) with vestibular schwannoma (VS) GRS patients. Patients who were treated with GRS between July and November 2021 were included. Patient, tumor, and dosimetric characteristics were retrospectively summarized and analyzed. Forty-one patients with 48 intracranial tumors were included. Tumor entities mostly comprised VS, brain metastases, and meningiomas. The median prescription dose and isodose line were 13.5Gy and 50.0% for benign neoplasia versus 20Gy and 60.0% for malignant tumors, respectively. The mean planning target volume was 1.5 cubic centimeters. All patients received a single-fraction treatment without encountering any technical setup difficulties. Treatment plan comparisons with RRS revealed comparable plan characteristics, dose gradients, and organs at risk doses. Significant differences were detected concerning the new conformity index and number of monitor units per treatment (both P<0.01). This case series provides more evidence on the usage of self-shielding GRS in the management of cranial tumors. Dosimetric comparisons for VS cases revealed mostly equivalent dosimetric characteristics to RRS. Further clinical and physical analyses for GRS are underway.

Pattern of disease progression following stereotactic radiosurgery in malignant glioma patients

IntroductionThe clinical benefit of stereotactic radiosurgery (SRS) in the treatment of malignant glioma remains controversial. We analyzed failure patterns of malignant gliomas following SRS to identify the clinical implications of SRS against these malignancies. Materials and methodsWe retrospectively reviewed 58 consecutive patients who received SRS with a gamma knife for their malignant glioma from January 2013 to December 2018. A total of 51 patients were available for analysis of failure patterns. Failure patterns were defined by the recurrent tumors’ spatial relation to SRS target as follows: in-field local recurrence, remote recurrence, and leptomeningeal seeding. If patients demonstrated several types of failure patterns simultaneously, we categorized them as a combined failure pattern. ResultsIn-field local recurrence was found in 47.1% of patients. Other types of failure patterns were as follows: remote recurrence (19.6%), leptomeningeal seeding (13.7%), and combined failure pattern (19.6%). The majority of patients (52.9%) experienced disease progression beyond the radiation field of SRS, which implies limited efficacy of local therapy against these invasive tumors. The prognosis of patients differed according to failure pattern and patients with local recurrence had better survival outcomes compared to other types of disease progression (p-value = 0.0015, log-rank test). ConclusionsThis study illustrated that SRS could not improve survival of malignant gliomas significantly even when it had some effect within radiation field. Our findings support utilizing a multidisciplinary treatment strategy to improve the prognosis of malignant gliomas and suggest that SRS is one element of that treatment strategy.

SU-F-T-570: Comparison of Synthetic Diamond, Microionization Chamber, and Radiochromic Film for Absolute Dosimetry of VMAT Radiosurgery

Purpose: Patient specific quality assurance of stereotactic radiosurgery (SRS) plans is challenging because of small target sizes and high dose gradients. We compared three detectors for dosimetry of VMAT SRS plans. Methods: The dose at the center of seventeen targets was measured using a synthetic diamond detector (2.2 mm diameter, 1 µm thickness), a 0.007 cm3 ionization chamber, and radiochromic film. Measurements were made in a PMMA phantom in the clinical geometry – all gantry and table angles were delivered as planned. The diamond and chamber positions were offset by 1 cm from the film plane, so the isocenter was shifted accordingly to place the center of the target at the detector of interest. To ensure accurate detector placement, the phantom was positioned using kV images. To account for the shift-induced difference in geometry and differing prescription doses between plans, the measurements were normalized to the expected dose calculated by the treatment planning system. Results: The target sizes ranged from 2.8 mm to 34.8 mm (median 14.8 mm). The mean measurement-to-plan ratios were 1.054, 1.076, and 1.023 for RCF, diamond, and chamber, respectively. The mean difference between the chamber and film was −3.2% and between diamond and film was 2.2%. For targets larger than 15 mm, the mean difference relative to film was −0.8% and 0.1% for chamber and diamond, respectively, whereas for targets smaller than 15 mm, the difference was −5.3% and 4.2% for chamber and diamond, respectively. The difference was significant (p=0.005) using the two-sample Kolmogorov-Smirnov test. Conclusion: The detectors agree for target sizes larger than 15 mm. Relative to film, for smaller targets the diamond detector over-responds, whereas the ionization chamber under-responds. Further work is needed to characterize detector response in modulated SRS fields.

Quality of search strategies reported in systematic reviews published in stereotactic radiosurgery.

Systematic reviews require comprehensive literature search strategies to avoid publication bias. This study aimed to assess and evaluate the reporting quality of search strategies within systematic reviews published in the field of stereotactic radiosurgery (SRS). Three electronic databases (Ovid MEDLINE(®), Ovid EMBASE(®) and the Cochrane Library) were searched to identify systematic reviews addressing SRS interventions, with the last search performed in October 2014. Manual searches of the reference lists of included systematic reviews were conducted. The search strategies of the included systematic reviews were assessed using a standardized nine-question form based on the Cochrane Collaboration guidelines and Assessment of Multiple Systematic Reviews checklist. Multiple linear regression analyses were performed to identify the important predictors of search quality. A total of 85 systematic reviews were included. The median quality score of search strategies was 2 (interquartile range = 2). Whilst 89% of systematic reviews reported the use of search terms, only 14% of systematic reviews reported searching the grey literature. Multiple linear regression analyses identified publication year (continuous variable), meta-analysis performance and journal impact factor (continuous variable) as predictors of higher mean quality scores. This study identified the urgent need to improve the quality of search strategies within systematic reviews published in the field of SRS. This study is the first to address how authors performed searches to select clinical studies for inclusion in their systematic reviews. Comprehensive and well-implemented search strategies are pivotal to reduce the chance of publication bias and consequently generate more reliable systematic review findings.

Inception of a national multidisciplinary registry for stereotactic radiosurgery.

Stereotactic radiosurgery (SRS) represents a multidisciplinary approach to the delivery of ionizing high-dose radiation to treat a wide variety of disorders. Much of the radiosurgical literature is based upon retrospective single-center studies along with a few randomized controlled clinical trials. More timely and effective evidence is needed to enhance the consistency and quality of and clinical outcomes achieved with SRS. The authors summarize the creation and implementation of a national SRS registry. The American Association of Neurological Surgeons (AANS) through NeuroPoint Alliance, Inc., started a successful registry effort with its lumbar spine initiative. Following a similar approach, the AANS and NeuroPoint Alliance collaborated with corporate partners and the American Society for Radiation Oncology to devise a data dictionary for an SRS registry. Through administrative and financial support from professional societies and corporate partners, a framework for implementation of the registry was created. Initial plans were devised for a 3-year effort encompassing 30 high-volume SRS centers across the country. Device-specific web-based data-extraction platforms were built by the corporate partners. Data uploaders were then used to port the data to a common repository managed by Quintiles, a national and international health care trials company. Audits of the data for completeness and veracity will be undertaken by Quintiles to ensure data fidelity. Data governance and analysis are overseen by an SRS board comprising equal numbers of representatives from the AANS and NeuroPoint Alliance. Over time, quality outcome assessments and post hoc research can be performed to advance the field of SRS. Stereotactic radiosurgery offers a high-technology approach to treating complex intracranial disorders. Improvements in the consistency and quality of care delivered to patients who undergo SRS should be afforded by the national registry effort that is underway.

O04 * DIFFUSION WEIGHTED MRI DISCRIMINATES PRIMARY CANCER TYPE AND OUTCOME IN BRAIN METASTASES

INTRODUCTION: Diffusion weighted MRI (DWI) is a powerful technique for non-invasive assessment of many solid cancers. We investigated whether pre-operative DWI characteristics of cerebral metastases correlate with patient outcomes. METHOD: Retrospective analysis of 76 metastases with DWI performed pre-operatively at 1.5T. Apparent Diffusion Coefficient (ADC) maps were generated and measurements were taken from the tumour, peritumoral region, across the brain-tumour interface (ADC transition coefficient or (ATC)) and in normal white matter. Outcome measures were overall survival (OS) and time to local recurrence (PFS). Tissue was assessed to determine cellularity. RESULTS: ADC changes in the tumour and peritumoral region differed between metastases of different primaries. Metastases with higher tumour ADC values were associated with longer OS and PFS. This was also demonstrated in the most common brain metastasis, lung adenocarcinoma (n = 36). Tumours with a sharp change in ADC across their boundary (high ATC) had a significantly shorter OS, 6.8 months (95% CI 5.3 - 8.4) as compared to those with a low ATC and hence diffuse boundary (11.2 months, 95% CI 8.3 - 14.0, Log rank Chi-Square = 4.19, p = 0.041). The ATC was the only imaging metric which independently predicted overall survival in multivariate analysis (hazard ratio 0.54, 95% CI 0.3 - 0.97, p = 0.04). Cellularity was positively related to ATC and inversely related to tumour ADC. CONCLUSION: DWI demonstrates changes in the tumour, tumour edge and peritumoral region which are not visible on routine MRI. ADC maps could be used to predict patient outcomes more accurately and plan surgical margins or stereotactic radiosurgery fields.

Evaluation of linear accelerator (LINAC)-based stereotactic radiosurgery (SRS) for cerebral cavernous malformations: a 15-year single-center experience

BACKGROUND AND OBJECTIVESSurgery is the principal treatment for safely accessible hemorrhagic and symptomatic cavernous malformations. Nevertheless, the role of linear accelerator (LINAC)-based stereotactic radiosurgery (SRS) in the management of high-risk, symptomatic cavernoma lesions warrants further refinement. In this study, we evaluate the use of LINAC-based SRS for cerebral cavernous malformations (CMs) and report our 15-year single-center experience.DESIGN AND SETTINGSA retrospective study from the Department of Radiation Oncology and the Department of Neurosurgery at Gulhane Military Medical Academy and Medical Faculty, Ankara from April 1998 to June 2013.PATIENTS AND METHODSFifty-two patients (22 females and 30 males) with cerebral CM referred to our department underwent high-precision single-dose SRS using a LINAC with 6-MV photons. All patients had at least 1 bleeding episode prior to radiosurgery along with related symptoms. Median dose prescribed to the 85% to 95% isodose line encompassing the target volume was 15 Gy (range, 10–20).RESULTSOut of the total 52 patients, follow-up data were available for 47 patients (90.4%). Median age was 35 years (range, 19–63). Median follow-up time was 5.17 years (range, 0.08–9.5) after SRS. Three hemorrhages were identified in the post-SRS period. Statistically significant decrease was observed in the annual hemorrhage rate after radiosurgical treatment (pre-SRS 39% vs post-SRS 1.21, P<.0001). Overall, there were no radiosurgery-related complications resulting in mortality.CONCLUSIONLINAC-based SRS may be considered as a treatment option for high-risk, symptomatic cerebral CM of selected patients with prior bleeding from lesions located at surgically inaccessible or eloquent brain areas.

Best of International Stereotactic Radiosurgery Society Congress 2013: Stereotactic Body Radiation Therapy. Part II: Nonspinal Tumors

The 11th biennial International Stereotactic Radiosurgery Society Congress represented another historical gathering of professionals in the field of stereotactic radiosurgery. This congress was held on 16-20 June 2013 in Toronto (ON, Canada), and the chairman was Arjun Sahgal, co-chair was Michael Schwartz and president of the society was Jean Regis. The congress attracted 550 attendants from all over the world and over 300 abstracts were presented. Among the abstracts presented, 62 (36 oral) were pertaining to stereotactic body radiation therapy (SBRT). Exciting new findings were presented by colleagues from North America, Europe and Asia. This short conference scene (part II) provides a summary of the best abstracts on SBRT for nonspinal tumors presented in the congress. A separate conference scene on SBRT for spinal tumors (part I) also appears in this issue of Future Oncology.

Best of International Stereotactic Radiosurgery Society Congress 2013: Stereotactic Body Radiation Therapy. Part I: Spinal Tumors

The 11th biennial International Stereotactic Radiosurgery Society Congress represented another historical gathering of professionals in the field of stereotactic radiosurgery. This congress was held on 16-20 June 2013 in Toronto (ON, Canada), and the chairman was Arjun Sahgal, the co-chair was Michael Schwartz and president of the society was Jean Regis. The congress attracted 550 attendants from all over the world and over 300 abstracts were presented. Among the abstracts presented, 62 (36 oral) were pertaining to stereotactic body radiation therapy (SBRT). Exciting new findings were presented by colleagues from North America, Europe and Asia. This short conference scene (part I) provides a summary of the best abstracts on SBRT for spinal tumors presented in the congress. A separate conference scene on SBRT for nonspinal tumors (part II) also appears in this issue of Future Oncology.

SU‐GG‐T‐451: Clinical Evaluation of New BrainLab Image Guided Frameless SRS System

Purpose: To evaluate the results and accuracy of Image Guided Frameless SRS. Method and Materials: A new image guided frameless system for Novalis has been installed at our institution for Stereotactic Radiosurgery (SRS) treatment. The main features of the system are its utilization of an Infrared camera, a pair of kV x‐ray, and a 6D couch for patient setup. The system works at any couch angle. The tracking computer will generate DRRs for the corresponding couch angle and compares them with OBI kV images to determine the shift corrections in 6 Dimensions (3 Translational and 3 Rotational). The shift corrections are carried out by the 6D robotic couch, The same process is repeated to confirm the correction was successful, and that further correction is no longer needed. The same process is required for every couch angle during the SRS treatment. The SRS fields are shaped by employing either BrainLab micro MLC or BrainLab cones. We have treated various types of brain tumors including trigeminnal nerves. Results: The system is very intutive, and in general only one OBI guided frameless correction procedure is needed for each couch angle. The OBI kV images obtained for confirmation of correction on average show that the mean deviation by automatic imaging fusion computer are 0.5±1, 0.2±1 and 0.3±1 degree for pitch, roll and yaw, 0.3±0.3, 0.3±0.4, 0.2±0.8 mm for longitudinal, lateral and vertical translation movement. Included are the pre and post trigeminal nerve MRI scan that shows clearly that we hit the target of planned treatment. Conclusion: The new type of BrainLab' Image Guided Framless SRS system coupled with an 6D robotic couch, imaging at any couch angles, is accurate, and easy to use. Initial experience shows that clinical results are equivalent to the Frame based SRS system.

Techniques in dosimetry and 3‐D treatment planning for stereotactic radiosurgery/radiotherapy

The goal of this work was to improve stereotactic radiosurgery (SRS) dose calculation and dosimetry techniques.\sMonte Carlo techniques were used to calculate and PTW diamond detectors were used to measure SRS dose distributions.\sA method of calculating dose distribution using sector‐integration of Monte Carlo‐generated pencil beam kernels is proposed.\sThis technique can be used both for circular and irregular fields.\sIt is especially useful in calculating the dosimetry for irregular fields, where the shape of the treatment field is determined during planning.\sMonte Carlo techniques were confirmed as reliable references for calculation of the dose distribution of SRS fields.\sDiamond detectors were found to be potentially ideal for SRS.\sThey yield more accurate results than the commonly used silicon diodes, ionization chambers, film or thermoluminescence dosimetry.\sBioeffect planning, as a rather new approach, was introduced in which treatment plans can be evaluated according to the bioeffect distribution rather than the dose distribution.\sDose can be converted to biologically effective dose using the alpha/beta ratio from the linear‐quadratic model.\sEstimates of TCP and NTCP can also be obtained using the Alpha, Beta values, dose‐volume histogram data, and in the case of normal tissue the partial volume of the organ irradiated.