Image-guided Stereotactic Radiotherapy Research Articles

Impact of Fractionation Regimen on Local Control Following Frameless Linear Accelerator-Based Image-Guided Stereotactic Radiosurgery and Radiotherapy for Intracranial Meningioma

ObjectivesStereotactic radiosurgery (SRS) is an established treatment for intracranial meningioma, yet this approach is often precluded by tumor size or proximity to critical structures. Fractionated radiotherapy may be employed to address these limitations. We performed a comparison of local control (LC) outcomes between three stereotactic techniques. MethodsA retrospective review was performed of 543 consecutive patients with 613 histologically-proven WHO grade I or radiographically-defined benign intracranial meningioma treated with SRS (median dose: 1250cGy) (n=211), fractionated SRS (FSRS) (2500cGy in 500cGy fractions) (n=170), or conventionally fractionated stereotactic radiotherapy (FSRT) (median dose: 5022cGy in <200cGy fractions) (n=232) in the definitive (n=475) or post-operative (n=138) setting between January 2008 and December 2021. Post-operative treatment was delivered upfront after a subtotal resection (n=43) or for recurrent disease (n=95). ResultsMedian follow-up per lesion was 8.0 years. LC for all lesions at 5/10/14 years was 97.4%/86.8%/86.8%. Base of skull location (p=0.01), tumor volume >5cc (p=0.01), and recurrent disease (p=0.02) were associated with inferior LC. No difference was observed in LC by fractionation regimen; LC at 5/10 years was 97.3%/85.7% for SRS, 97.5%/89.1% for FSRS, and 97.5%/86.3% for FSRT. Dose escalation above 1250cGy for SRS or above 5040cGy for FSRT did not result in improved LC. ConclusionsDurable LC was observed at long-term follow-up of intracranial meningioma treated with stereotactic radiosurgery and radiotherapy. LC outcomes were similar across the three fractionation regimens, suggesting that clinicians may tailor radiotherapy recommendations based on clinical factors without concern for reduced efficacy.

Geometric accuracy in patient positioning for stereotactic radiotherapy of intracranial tumors.

This study determines and compares the geometric setup errors between stereoscopic x-ray and kilo-voltage cone beam CT (CBCT) in phantom tests on a linear accelerator (linac) for image-guided (IG) stereotactic radiotherapy of intracranial tumors. Additionally, dose-volume metrics in the target volumes of the setup errors of CBCT were evaluated. A Winston-Lutz- and an anthropomorphic phantom were used. The mean deviation and root mean square error (RMSE) of CBCT and stereoscopic x-ray were compared. Dose-volume metrics of the planning target volume (PTV) and gross target volume (GTV) for CBCT were calculated. The RMSEs in the tests with the Winston-Lutz-Phantom were 0.3mm, 1.1mm and 0.3mm for CBCT and 0.1mm, 0,1 mm and<0.1mm for stereoscopic x-ray in the translational dimensions (right-left, anterior-posterior and superior-inferior). The RMSEs in the tests with the anthropomorphic phantom were 0.3mm, 0.2mm and 0.1mm for CBCT and 0.1mm, 0,1 mm and<0.1mm for stereoscopic x-ray. The effects on dose-volume metrics of the setup errors of CBCT on the GTV were within 1 % for all considered dose values. The effects on the PTV were within 5 % for all considered dose values. Both IG systems provide high accuracy patient positioning within a submillimeter range. The phantom tests exposed a slightly higher accuracy of stereoscopic x-ray than CBCT. The comparison with other studies with a similar purpose emphasizes the importance of individual IG installation quality assurance.

Long-term progression-free survival in a patient with inoperable pancreatic cancer following image-guided stereotactic ablative radiotherapy

Long-term progression-free survival in a patient with inoperable pancreatic cancer following image-guided stereotactic ablative radiotherapy

142: Assessment of Intrafraction Motion for Spine and Non-Spine Bone Metastases Treated with Image-Guided Stereotactic Ablative Radiotherapy Without 6 Degrees-of-Freedom Couch Correction

142: Assessment of Intrafraction Motion for Spine and Non-Spine Bone Metastases Treated with Image-Guided Stereotactic Ablative Radiotherapy Without 6 Degrees-of-Freedom Couch Correction

Single-institutional outcome-analysis of low-dose stereotactic body radiation therapy (SBRT) of adrenal gland metastases

BackgroundAdrenal gland metastases are a common diagnostic finding in various tumor diseases. Due to the increased use of imaging methods, they are diagnosed more frequently, especially in asymptomatic patients. SBRT has emerged as a new, alternative treatment option in the field of radiation oncology. In the past, it was often used for treating inoperable lung, liver, prostate, and brain tumors. Meanwhile, it is also an established keystone in the treatment of oligometastatic diseases. This retrospective study aims to evaluate the effect of low-dose SBRT in patients with adrenal metastases.MethodsWe analyzed a group of 31 patients with 34 adrenal gland lesions treated with low-dose SBRT between July 2006 and July 2019. Treatment-planning was performed through contrast-enhanced CT, followed by image-guided stereotactic radiotherapy using cone-beam CT. The applied cumulative median dose was 35 Gy; the median single dose was 7 Gy. We focused on local control (LC), progression-free survival (PFS), overall survival (OS), as well as acute and late toxicity.ResultsSeven adrenal gland metastases (20.6%) experienced local failure, 80.6% of the patients faced a distant progression. Fourteen patients were still alive. Median follow-up for all patients was 9.8 months and for patients alive 14.4 months. No treatment-related side-effects >grade 2 occurred. Of all, 48.4% suffered from acute gastrointestinal disorders; 32.3% reported acute fatigue, throbbing pain in the renal area, and mild adrenal insufficiency. Altogether, 19.4% of the patients faced late-toxicities, which were as follows: Grade 1: 12.9% gastrointestinal disorders, 3.2% fatigue, Grade 2: 9.7% fatigue, 6.5% headache, 3.2% loss of weight. The 1-year OS and probability of LF were 64 and 25.9%, respectively.ConclusionLow-dose SBRT has proven as an effective and safe method with promising outcomes for treating adrenal metastases. There appeared no high-grade toxicities >grade 2, and 79.4% of treated metastases were progression-free. Thus, SBRT should be considered as a therapy option for adrenal metastases as an individual therapeutic concept in the interdisciplinary discussion as an alternative to surgical or systemic treatment.

Intrafractional 6D head movement increases with time of mask fixation during stereotactic intracranial RT-sessions

BackgroundThe present study investigates the intrafractional accuracy of a frameless thermoplastic mask used for head immobilization during stereotactic radiotherapy. Non-invasive masks cannot completely prohibit head movements. Previous studies attempted to estimate the magnitude of intrafractional inaccuracy by means of pre- and postfractional measurements only. However, this might not be sufficient to accurately map also intrafractional head movements.Materials and methodsIntrafractional deviation of mask-fixed head positions was measured in five patients during a total of 94 fractions by means of close-meshed repeated ExacTrac measurements (every 1.4 min) conducted during the entire treatment session. A median of six (range: 4 to 11) measurements were recorded per fraction, delivering a dataset of 453 measurements.ResultsRandom errors (SD) for the x, y and z axes were 0.27 mm, 0.29 mm and 0.29 mm, respectively. Median 3D deviation was 0.29 mm. Of all 3D intrafractional motions, 5.5 and 0.4% exceeded 1 mm and 2 mm, respectively. A moderate correlation between treatment duration and mean 3D displacement was determined (rs = 0.45). Mean 3D deviation increased from 0.21 mm (SD = 0.26 mm) in the first 2 min to a maximum of 0.53 mm (SD = 0.31 mm) after 10 min of treatment time.ConclusionPre- and post-treatment measurement is not sufficient to adequately determine the range of intrafractional head motion. Thermoplastic masks provide both reliable interfractional and intrafractional immobilization for image-guided stereotactic hypofractionated radiotherapy. Greater positioning accuracy may be obtained by reducing treatment duration (< 6 min) and applying intrafractional correction.Trial registrationClinicaltrials.gov, NCT03896555, Registered 01 April 2019 - retrospectively registered.

197. Stereotactic Body Radiotherapy: Comparison between two IGRT systems

Purpose The aim of this work is to compare the residual setup errors measured with ExacTrac X-ray 6 degree-of-freedom (6D) and kilo-voltage cone-beam computed tomography (CBCT) for patients receiving stereotactic body radiotherapy (SBRT) at Fondazione IOM in collaboration with REM Radioterapia. The first device employs an infrared optical system that performs patients pre-positioning through body markers and isocenter coordinates, and an X-ray imaging system that verifies target position using bone anatomy. CBCT imaging allows positioning verification using not only bone anatomy but also soft tissues. Methods On a TrueBeam-Novalis STx treatment unit, from January to November 2017, 45 patients with extracranial tumours were treated with SBRT for a total of 53 lesions (some patients having more than one lesion) and 152 treatment sessions. Prescribing doses ranged from 24 to 60 Gy in 3 fractions or 20 Gy in a single fraction and planning techniques were dynamic conformal arc therapy or hybrid intensity modulated radiotherapy, with no-coplanar fields. All patients were initially located using personalized immobilization systems and setup corrections were determined and corrected by means of registrations of ExacTrac X-ray images with the corresponding digitally reconstructed radiographs using the ExacTrac 6D fusion. At the end of each treatment session, with the couch at 0°, the residual setup errors were determined by means of registrations of CBCT images with the planning CT using online 3D fusion and for each session, displacements were evaluated to analyse the residual setup errors. Results A modest difference in residual setup errors was found between ExacTrac system and CBCT (figure below). The average of the observed residual displacements for the three space directions, in absolute value, was 1.5 mm in vertical and in lateral directions, 1.2 mm in longitudinal direction. Conclusion This work showed the good agreement on the setup accuracy between ExacTrac X-ray and CBCT for patients treated with SBRT. The two systems present comparable precision, but ExacTrac offers additional benefits such the capability to quantify all rotational errors, fastest automated positioning in 6D even for no-coplanar fields and smaller doses, representing a valid alternative to CBCT with complementary information in image-guided stereotactic radiotherapy.

Introduction of image-guided stereotactic radiotherapy systems for small animals

The theory and application of small animal radiotherapy models is critical for the research and development of radiobiology and clinical radiotherapy. Considering universality and cost effects, mouse models are widely used to explore the radiobiological mechanisms of cancerous and normal tissues. In recent years, there has been tremendous progress in image-guided stereotactic radiotherapy equipment for small animals, which could simulate the human radiotherapy process. This article introduces stereotactic radiotherapy systems for small animals guided by different imaging modalities, such as cone-beam computed tomography and magnetic resonance imaging, and then reviews small animal fluorescence imaging technology and summarizes the application of different bioluminescence and fluorescence imaging equipment in small animal imaging systems. Finally, we put forward the prospect of optimization direction of radiotherapy equipment for small animals in future. Key words: Small animal radiotherapy system; Bioluminescence and Fluorescence; Reconstruction

Stereotactic ablative body radiotherapy for non-small-cell lung cancer: setup reproducibility with novel arms-down immobilization.

A clinical evaluation of the intrafraction and interfraction setup accuracy of a novel thermoplastic mould immobilization device and patient position in early-stage lung cancer being treated with stereotactic radiotherapy at the Beatson West of Scotland Cancer Centre, Glasgow, UK. 35 patients were immobilized in a novel, arms-down position, with a four-point Klarity™ (Klarity Medical Products, Ohio, US) clear thermoplastic mould fixed to a SinMed (CIVCO Medical solutions, lowa, US) head and neck board. A knee support was also used for patient comfort and support. Pre- and post-treatment kilovoltage cone beam CT (CBCT) images were fused with the planning CT scan to determine intra- and interfraction motion. A total of 175 CBCT scans were analysed in the longitudinal, vertical and lateral directions. The mean intrafraction errors were 0.05 ± 0.77 mm (lateral), 0.44 ± 1.2 mm (superior-inferior) and -1.44 ± 1.35 mm (anteroposterior), respectively. Mean composite three-dimensional displacement vector was 2.14 ± 1.2 mm. Interfraction errors were -0.66 ± 2.35 mm (lateral), -0.13 ± 3.11 mm (superior-inferior) and 0.00 ± 2.94 mm (anteroposterior), with three-dimensional vector 4.08 ± 2.73 mm. Setup accuracy for lung image-guided stereotactic ablative radiotherapy using a unique immobilization device, where patients have arms by their sides, has been shown to be safe and favourably comparable to other published setup data where more complex and cumbersome devices were utilised. There was no arm toxicity reported and low arm doses. Advances in knowledge: We report on the accuracy of a novel patient immobilization device.

Reirradiation using robotic image-guided stereotactic radiotherapy of recurrent head and neck cancer.

The purpose of this study was to examine the prognosis for patients with head and neck cancer after reirradiation using Cyberknife stereotactic body irradiation with special focus on mucosal ulceration. We conducted a retrospective multi-institutional review of 107 patients with previously irradiated head and neck cancer. The median follow-up time for all patients was 15 months, and the 2-year overall survival rate was 35%. Significant prognostic factors for overall survival were primary site (nasopharynx versus other sites), presence of ulceration, and PTV volume. Detailed analysis of ulceration showed a lower response rate (28%) in the ulceration (+) group than the ulceration (−) group (63%; P = 0.0045). The 2-year overall survival rates were 8% in the ulceration (+) group and 42.7% (P = 0.0001) in the ulceration (−) group, respectively. We recorded 22 severe toxicities, including 11 patients with carotid blow-out syndrome (CBOS), which was fatal in 9 patients. CBOS occurred in 6 patients with ulceration (6/25; 24%), and 5 patients experienced CBOS without ulceration (5/82; 6%; P=0.027). In conclusion, ulceration is an important prognostic factor, not only for adverse events but also for survival after reirradiation using CyberKnife.

Changes in Pulmonary Function Following Image-Guided Stereotactic Lung Radiotherapy: Neither Lower Baseline Nor Post-SBRT Pulmonary Function Are Associated with Worse Overall Survival

To determine changes in pulmonary function brought about by lung stereotactic body radiation therapy (SBRT). One hundred and twenty-seven patients were treated with lung SBRT using 48 to 60Gy in four to five fractions on a prospective trial. We obtained pulmonary function tests (PFTs) at baseline, 6 weeks, 3 months, 6 months, 9 months, 12 months, and 24 months after SBRT. Group mean PFT parameter values are reported. At baseline forced expiratory volume in 1 second (FEV1) was 1.5 l (67% predicted, range: 0.4-3.4 l), corrected diffusing capacity for carbon monoxide was 12.2 ml/min/mmHg (50.8% predicted, range: 3.3-27.2 ml/min/mmHg), and total lung capacity was 5.7 l (102.4% predicted, range: 3.1-9.1 l). At 12 months, there was decline in FEV1 (-4.1%; p = 0.01), corrected diffusing capacity for carbon monoxide (-5.2%; p = 0.027), forced vital capacity (-5.7%; p = 0.004), and total lung capacity (-3.6%; p = 0.039). Declines in FEV1 (-7.6%; p = 0.001) and forced vital capacity (-8.9%; p = 0.001) persisted at 24 months. Rates of pneumonitis were 3.1% and 0.8% for grades 2 and 3, respectively. There were no grade 3 PFT toxicities at 12 months. Lower PFTs at baseline and 1 year after SBRT did not predict for worse overall survival. As the largest cohort of patients with prospective follow-up PFT evaluation after lung SBRT, this supports the safety of SBRT in this population of predominantly medically inoperable patients. While statistically significant, nearly all declines in PFTs would be rated as a grade 1 on the Radiation Therapy Oncology Group scale, demonstrating safety. PFT declines were not associated with worse overall survival.

Outcome of Elderly Patients with Meningioma after Image-Guided Stereotactic Radiotherapy: A Study of 100 Cases.

Introduction. Incidence of meningioma increases with age. Surgery has been the mainstay treatment. Elderly patients, however, are at risk of severe morbidity. Therefore, we conducted this study to analyze long-term outcomes of linac-based fractionated stereotactic radiotherapy (FSRT) for older adults (aged ≥65 years) with meningioma and determine prognostic factors. Materials and Methods. Between October 1998 and March 2009, 100 patients (≥65, median age, 71 years) were treated with FSRT for meningioma. Two patients were lost to follow-up. Eight patients each had grade I and grade II meningiomas, and five patients had grade III meningiomas. The histology was unknown in 77 cases (grade 0). Results. The median follow-up was 37 months, and 3-year, 5-year, and 10-year progression-free survival (PFS) rates were 93.7%, 91.1%, and 82%. Patients with grade 0/I meningioma showed 3- and 5-year PFS rates of 98.4% and 95.6%. Patients with grade II or III meningiomas showed 3-year PFS rates of 36%. 93.8% of patients showed local tumor control. Multivariate analysis did not indicate any significant prognostic factors. Conclusion. FSRT may play an important role as a noninvasive and safe method in the clinical management of older patients with meningioma.

Image-guided stereotactic ablative radiotherapy for the liver: A safe and effective treatment

AimsStereotactic ablative body radiotherapy (SABR) is a non-invasive treatment option for inoperable patients or patients with irresectable liver tumors. Outcome and toxicity were evaluated retrospectively in this single-institution patient cohort. Patients and methodsBetween 2010 and 2014, 39 lesions were irradiated in 33 consecutive patients (18 male, 15 female, median age of 68 years). All the lesions were liver metastases (n = 34) or primary hepatocellular carcinomas (n = 5). The patients had undergone four-dimensional respiration-correlated PET-CT for treatment simulation to capture tumor motion. We analyzed local control with a focus on CT-based response at three months, one year and two years after treatment, looking at overall survival and the progression pattern. ResultsAll patients were treated with hypofractionated image-guided stereotactic radiotherapy. The equivalent dose in 2 Gy fractions varied from 62.5 Gy to 150 Gy, delivered in 3–10 fractions (median dose 93.8 Gy, alpha/beta = 10). The CT-based regression pattern three months after radiotherapy revealed partial regression in 72.7% of patients with a complete remission in 27.3% of the cases. The site of first progression was predominantly distant. One- and two-year overall survival rates were 85.4% and 68.8%, respectively. No toxicity of grade 2 or higher according to the NCI Common Terminology Criteria for Adverse Events v4.0 was observed. ConclusionSABR is a safe and efficient treatment for selected inoperable patients or irresectable tumors of the liver. Future studies should combine SABR with systemic treatment acting in synergy with radiation, such as immunological interventions or hypoxic cell radiosensitizers to prevent distant relapse.

Meningioma of the skull base: Long-term outcome after image-guided stereotactic radiotherapy

PurposeThe purpose of this study was to analyse the feasibility, safety, and long-term efficacy of linear accelerator-based fractionated stereotactic radiotherapy for meningiomas of the skull base. We evaluated the long-term clinical outcome of patients and identified prognostic factors after fractionated stereotactic radiotherapy. Patients and methodsBetween 10/1995 and 03/2009, 136 patients with a median age of 57 years with skull base meningioma received fractionated stereotactic radiotherapy. A total of 34 patients had a grade I meningioma, in 102 cases no histology was obtained (grade 0). Fractionated stereotactic radiotherapy was delivered as primary treatment for 57 patients and postoperatively for 79. The patients received a mean total dose of 56.95 (min/max 32.4/63)Gy. ResultsMedian follow-up was 44.9 months. Overall progression-free survival was 96.9% after 3 years, 93.8% after 5 years, and 91.5% after 10 years. Patients with unknown histology showed progression-free survival rates of 100%, 98.7%, and 93.5% at 3, 5, and 10 years and patients with biopsy-proven grade I meningioma showed rates of 100% after 3 years, 91.7% after 5 years and 85.9% after 10 years. Patients with adjuvant radiotherapy showed significantly worse progression-free survival rates than patients who had been treated with primary radiotherapy (P=0.043), progression-free survival rates were independent of tumour size. The most common acute grade I symptoms were headache, fatigue, and local alopecia. The most common chronic grade I symptoms were fatigue and headache. ConclusionsThis large study showed that fractionated stereotactic radiotherapy is an effective and safe treatment modality with high progression-free survival rates for intracranial meningioma. We identified “prior surgery” as significant poor prognostic factor.

Abstract 721: Suppression of orthotopic liver cancers by a combinatorial therapy of radiation and adenoviral vectors expressing interleukin 12

Abstract Hepatocellular carcinoma (HCC) is one of the leading causes of cancer death worldwide. Because of difficulty in early diagnosis, only a minority of HCC patients are candidates for resection or transplantation, the traditional curative treatments. Recent development of image-guided radiotherapy and stereotactic radiotherapy offer an alternative therapeutic option for HCC patients with advanced diseases. In addition to eradicate tumor cells via DNA double-strand breaks or induction of apoptosis, radiotherapy also induces immunogenic tumor cell death, releasing a variety of danger-signaling molecules, which may help induce adaptive immune responses against the irradiated local tumors as well as the non-irradiated metastatic tumors. To further increase the therapeutic effect and enhance the antitumor immune responses, we proposed to combine radiation therapy with interleukin 12 (IL-12), a cytokine which has the ability to sensitize suppressive tumor-associated bone marrow-derived stromal cells, enhancing their ability to stimulate CD4+ and CD8+ T cell responses. BALB/c mice were injected at the left liver lobe of 3 x 105 BNL cells, a murine HCC cell line. At day 10, when the tumor volume reaching about 50 mm3, the hepatic tumors were receiving the following treatment: (1) a single dose of radiation of 10 Gy delivering at a mean dose rate of 6.72 Gy/min, (2) a single intratumoral injection of 108 p.f.u. of adenoviral vectors encoding a single-chain murine IL-12 (Ad/IL-12), (3) a combination therapy of 10 Gy radiation and 108 p.f.u. Ad/IL-12, and (4) no treatment. At day 30, mice were sacrificed and the tumor volume was measured by a caliper. The tumors in the control none treated group grew progressively with a mean tumor volume of 2,797 ± 304 mm3. The single treatment of radiation or Ad/IL-12 resulted in objective tumor growth suppression, reducing the mean tumor volume to 367 ± 203 mm3 and 241 ± 204 mm3, respectively, but none of the tumors were regressed after the single agent treatment. In contrast, the combinatorial treatment of radiation and Ad/IL-12 led to a partial (&amp;gt; 50% regression) or complete tumor regression in 80% (8 of 10) of tumors and substantially delayed tumor growth in the tumor-bearing mice. Our preliminary data also showed that the combinatorial treatment of radiation and Ad/IL-12 induced antitumor immune responses and suppressed systemic metastasis. Mechanistic studies of the combinatorial treatment of radiation and Ad/IL-12 are under investigation. Our results suggest that a combinatorial treatment of radiation and IL-12 may represent an alternative therapy for advanced HCC. Citation Format: Mi-Hua Tao, Wen-Shan Tsao, Ping-Yi Wu. Suppression of orthotopic liver cancers by a combinatorial therapy of radiation and adenoviral vectors expressing interleukin 12. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 721. doi:10.1158/1538-7445.AM2014-721

The impact of 18 F-FET PET-CT on target definition in image-guided stereotactic radiotherapy in patients with skull base lesions.

Background18 F-fluoro-ethyl-tyrosine PET is gaining more indications in the field of oncology. We investigated the potentials of usage of FET-PET/CT in addition to MRI for definition of gross tumor volume (GTV) in stereotactic radiotherapy of lesions of skull base.MethodsWe included in a prospective setting 21 cases. An MRI was performed, completed by FET PET/CT. Different GTV’s were defined based on respective imaging tools: 1. GTVMRI, 2. GTV MRI /CT, 3. GTV composit (1 + 2), and GTVPET = GTV Boost. Lesions could be visualised by MRI and FET-PET/CT in all patients.ResultsFET tracer enhancement was found in all cases. Skull base infiltration by these lesions was observed by MRI, CT (PET/CT) and FET-PET (PET/CT) in all patients. Totally, brain tissue infiltration was seen in 10 patients. While, in 7 (out 10) cases, MRI and CT (from PET/CT) were indicating brain infiltration, FET-PET could add additional information regarding infiltrative behaviour: in 3 (out 10) patients, infiltration of the brain was displayed merely in FET-PET. An enlargement of GTVMRI/CT due to the FET-PET driven information, which revealed GTVcomposite , was necessary in 7 cases,. This enlargement was significant by definition (> 10% of GTVMRI/CT). The mean PET-effect on GTV counted for 1 ± 4 cm3. The restricted boost fields were based mainly on the GTVPET volume. In mean, about 8.5 cm3 of GTVMRI/CT, which showed no FET uptake, were excluded from target volume. GTVboost driven by only-PET-activity, was in mean by 33% smaller than the initial large treatment field, GTVcomposite, for those cases received boost treatment. FET-PET lead to significant (>10%) changes in the initial treatment fields in 11/21 patients and showed additional tumour volume relevant for radiation planning in 6/21 cases, and led to a subsequent decrease of more than 10% of the initial volumes for the boost fields.ConclusionThe implementation of FET PET into the planning procedures showed a benefit in terms of accurate definition of skull base lesions as targets for Image-guided stereotactic Radiotherapy. This has to be investigated prospectively in larger cohorts.

Image-guided stereotactic radiotherapy for patients with vestibular schwannoma

Local tumor control and functional outcome after linac-based stereotactic radiosurgery (SRS) and fractionated stereotactic radiotherapy (FSRT) for vestibular schwannoma (VS) were assessed. In all, 250 patients with VS were treated: 190patients with tumors < 2cm diameter underwent SRS and 60patients with tumors >2 to 3.5cm underwent FSRT. Dose prescription for all cases with SRS (n = 190, 76 %) was 13.5Gy. For FSRT, mainly two hypofractionated schedules (n = 60, 24 %) with either 7fractions of 5Gy (total dose: 35Gy; n = 35) or 11fractions of 3.8Gy (total dose: 41.8Gy; n = 16) were used. The primary endpoint was local tumor control. Secondary endpoints were symptomatic control and morbidity. The median follow-up was 33.8months. The 3-year local tumor control was 88.9 %. Local control for SRS and FSRT was 88 and 92 %, respectively. For FSRT with 35 and 41.8Gy, local control was 90 and 100 %, respectively. There were no acute reactions exceeding gradeI. In 61cases (24.4 % of the entire cohort), trigeminal neuralgia was reported prior to treatment. At last follow-up, 16.3 % (10/61) of those patients reported relief of pain. Regarding facial nerve dysfunction, 45patients (18 %) presented with symptoms prior to RT. At the last follow-up, 13.3% (6/45) of those patients reported a relief of dysesthesia. Using SRS to treat small VS results in good local control rates. FSRT for larger lesions also seems effective. Severe treatment-related complications are not frequent. Therefore, image-guided stereotactic radiotherapy is an appropriate alternative to microsurgery for patients with VS.

Commissioning and initial stereotactic ablative radiotherapy experience with Vero

The purpose of this study is to describe the comprehensive commissioning process and initial clinical performance of the Vero linear accelerator, a new radiotherapy device recently installed at UT Southwestern Medical Center specifically developed for delivery of image‐guided stereotactic ablative radiotherapy (SABR). The Vero system utilizes a ring gantry to integrate a beam delivery platform with image guidance systems. The ring is capable of rotating ± 60° about the vertical axis to facilitate noncoplanar beam arrangements ideal for SABR delivery. The beam delivery platform consists of a 6 MV C‐band linac with a 60 leaf MLC projecting a maximum field size of 15×15 cm2 at isocenter. The Vero planning and delivery systems support a range of treatment techniques, including fixed beam conformal, dynamic conformal arcs, fixed gantry IMRT in either SMLC (step‐and‐shoot) or DMLC (dynamic) delivery, and hybrid arcs, which combines dynamic conformal arcs and fixed beam IMRT delivery. The accelerator and treatment head are mounted on a gimbal mechanism that allows the linac and MLC to pivot in two dimensions for tumor tracking. Two orthogonal kV imaging subsystems built into the ring facilitate both stereoscopic and volumetric (CBCT) image guidance. The system is also equipped with an always‐active electronic portal imaging device (EPID). We present our commissioning process and initial clinical experience focusing on SABR applications with the Vero, including: (1) beam data acquisition; (2) dosimetric commissioning of the treatment planning system, including evaluation of a Monte Carlo algorithm in a specially‐designed anthropomorphic thorax phantom; (3) validation using the Radiological Physics Center thorax, head and neck (IMRT), and spine credentialing phantoms; (4) end‐to‐end evaluation of IGRT localization accuracy; (5) ongoing system performance, including isocenter stability; and (6) clinical SABR applications.PACS number: 87.53.Ly

Image-guided robotic stereotactic radiotherapy for synchronous cancer of maxillary gingiva and lung

The use of stereotactic body radiation therapy is rapidly increasing among patients with lung cancer not amenable to surgery. The authors report their experience using the CyberKnife system (Accuray Inc., Sunnyvale, CA, USA) as a treatment option for synchronous cancer of oral squamous cell carcinoma and a malignant lung tumour. An 88-year-old woman with two cancers (oral and lung masses) underwent CyberKnife treatment, with fiducial gold pins implanted using bronchoscopy. Toxicity was limited, and at the 2-year follow-up the lesions had not recurred.

Clinical development of Stereotactic ablative body radiotherapy (SABR-SBRT) with non-dedicated multivendor technologies

Image guided stereotactic radiotherapy (IGRT) is a treatment modality that combines a variety of new technologies from imaging, to treatment planning and treatment delivery. It has been the primary method of treatment for several cranial and extra cranial tumors, where accurate patient immobilization and setup, tumor delineation, complex treatment planning and pre-treatment imaging, are necessary for accurate treatment delivery. One important benefit of the introduction of IGRT in the clinic has been the transition to Stereotactic Ablative radiotherapy (SABR-SBRT).