Hypofractionated stereotactic radiotherapy for brain metastases: a dosimetric and treatment efficiency comparison between volumetric modulated arc therapy and intensity modulated radiotherapy

Validation of esophageal cancer treatment methods from 3D-CRT, IMRT, and Rapid Arc plans using custom Python software to compare radiobiological plans to normal tissue integral dosage

Background

The aim was to develop in-house software that is able to calculate and generate the biological plan evaluation of the esophagus treatment plan using the Niemierko model for normal tissue complication probability and tumor control probability. The Niemierko model can be applied for esophagus cancer treatment plan to estimate the tumor control probability (TCP) and the normal tissue complication probability (NTCP) using different planning techniques. The equivalent uniform dose (EUD) and effective volume parameters were compared with organ at risk. Subsequently, EUD and TCP parameter were compared with tumor volume for all five different planning techniques.

Materials and methods

Ten cases for esophageal cancer were included in this study. For each patient, five treatment plans were generated. The Anisotropic analytical algorithms (AAA) were used for dose calculation for the three-dimensional conformal radiation therapy (3D-CRT), intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) techniques. The in-house developed radiobiological plan evaluation software using python programming is used for this study which takes a dose volume histogram (DVH) text file as an input file for biological plan evaluation.

Results and Conclusion

EUD, NTCP, TCP and effective volume were calculated from the Niemierko model using the in-house developed python based software and compared with treatment monitor units (MU) with all five different treatment plan. The best technique is quantified as benchmarked out of other different qualities of treatment. The four field 3D-CRT treatment plan is found to be the best suited from the perspective of biological plan index evaluation among the other planning techniques.

Frameless Stereotactic Radiosurgery With Linear Accelerator (LINAC)-Based Technology for Brain Metastases: Outcomes Analysis in 141 Patients

Objectives Brain metastases (BM) are the most common intracranial tumors in adults. Surgery and frame-based stereotactic radiosurgery (SRS) are well-described treatment options. Frameless SRS is an emerging BM treatment option offering fewer side effects. The aim of this study was to describe the therapeutic outcomes and toxicity of frameless SRS with linear accelerator (LINAC)-based technology for BM treatment in our institution. Materials and methods We performed a retrospective study including all adult patients treated with frameless SRS with LINAC-based technology for BM between October 2010 and July 2016. Patients were followed routinely with MRI scans at three-month intervals. Primary endpoints were progression-free survival, local control, overall survival, and toxicity related to the treatment. All survival times were computed with the Kaplan-Meier method. All cumulative incidences were computed using competing risk analyses. Results A total of 194 metastatic lesions in 141 patients were treated in a 69-month interval. At the time of analysis, 33 patients were still alive, with a median follow-up time of 25.1 months. The overall median survival was 8.7 months. The median progression-free survival was 5.3 months. Local recurrence as a first event was 25% and 38% at one and two years, respectively, while distant brain recurrence as a first event was 18% and 21%. Death before any brain event occurred in 31% of patients. The cumulative incidence of radiation necrosis as a first brain event was 2% at one and two years. Conclusions The treatment of BM with LINAC-based frameless SRS in our institution had an overall and progression-free survival comparable with the literature for frameless SRS and for conventional frame-based SRS while being less invasive and more comfortable for the patient. In our study, frameless SRS with LINAC technology seems to be safe for BM treatment with minimal rates of radiation necrosis.

Radiosurgery and stereotactic irradiation of multiple and contiguous brain metastases: A practical proposal of dose prescription methods and a literature review

PURPOSE

In literature, there are no guidelines on how to prescribe dose in the case of radiosurgery (SRS) or stereotactic irradiation of multiple and adjacent BM. Aim of this work is to furnish practical proposals of dosimetric methods for multiple neighboring BM, and to make a literature review about the SRS treatment of multiple BM, comparing radiotherapy techniques on the basis of different dosimetric parameters.

MATERIALS AND METHODS

A theoretical proposal of dosimetric approaches to prescribe dose in case of multiple contiguous BM is done. A literature review between 2010 and 2020 was performed on MEDLINE and Cochrane databases according to the PRISMA methodology, with the following keywords dose prescription, radiosurgery, multiple BM. Papers not reporting dosimetric solutions to irradiate multiple BM were excluded.

RESULTS

Only one article in the literature reports a practical modality of dose prescription for multiple adjacent BM. Thus, we proposed other five practical solutions to prescribe radiation dose in case of two or more neighboring BM, describing advantages and drawbacks of each method in terms of different dosimetric parameters. The literature review about dosimetric solutions to irradiate multiple BM led to 56 titles; 14 articles met the chosen criteria and we reported their results in terms of dosimetric indexes and low doses to the normal brain tissue.

CONCLUSIONS

The six dosimetric approaches here described can be used by physicians for multiple contiguous BM, depending on the clinical situation. These methods may be applied in clinical studies to better evaluate their usefulness in practice.

Significant correlation between gross tumor volume (GTV) D98% and local control in multifraction stereotactic radiotherapy (MF-SRT) for unresected brain metastases

BACKGROUND

Stereotactic radiotherapy (SRT) should be applied with a biologically effective dose with an α/β of 12 (BED₁₂) ≥ 40 Gy to reach a 1-year local control (LC) ≥ 70%. The aims of this retrospective study were to report a series of 81 unresected large brain metastases treated with Linac-based multifraction SRT according to the ICRU 91 and to identify predictive factors associated with LC.

METHODS

Included in this study were the first 81 brain metastases (BM) consecutively treated with Linac-based volumetric modulated arc therapy (VMAT) multifraction SRT from 2017 to 2019. The prescribed dose was 33 Gy for the GTV and 23.1 Gy (70% isodose line) for the PTV in 3 fractions (3f). Mean BM largest diameter and GTV were 25.1 mm and 7.2 cc respectively. Mean follow-up was 10.2 months.

RESULTS

LC was 79.7% and 69.7% at 1 and 2 years respectively. Significant predictive factors of LC were GTV D_98% (HR = 0.84, CI 95% = 0.75-0.95, p = 0.004) and adenocarcinoma as the histological type (HR = 0.29, CI 95% = 0.09-0.96, p = 0.042) in univariate and multivariate analysis. A threshold of 29 Gy for GTV D_98% was significantly correlated to LC (1-year LC = 91.9% for GTV D_98% ≥ 29 Gy vs 69.6% for GTV D_98% < 29 Gy (p = 0.030)), corresponding to a BED₁₂ = 52.4 Gy. No tumor progression was observed for a BED₁₂ ≥ 53.4 Gy, corresponding to a GTV D_98% ≥ 20 Gy /1f and GTV D_98% ≥ 29.4 Gy 3f. Median OS was 15 months. Symptomatic radionecrosis occurred in 4.9% of cases.

CONCLUSION

The GTV D_98% is a strong reproducible significant predictive factor of LC for brain SRT. Dose prescription should lead to a GTV BED_{12 98%} ≥ 52.4-53.4 Gy to significantly improve LC, corresponding to respectively a GTV D_98% ≥ 19.7-20 Gy/1f and 29-29.4 Gy/3f.

Hypofractionated stereotactic radiotherapy for large brain metastases: Optimizing the dosimetric parameters

PURPOSE

Stereotactic radiotherapy plays a major role in the treatment of brain metastases (BM). We aimed to compare the dosimetric results of four plans for hypofractionated stereotactic radiotherapy (HFSRT) for large brain metastases.

MATERIAL AND METHODS

Ten patients treated with upfront NovalisTx® non-coplanar multiple dynamic conformal arcs (DCA) HFSRT for≥25mm diameter single BM were included. Three other volumetric modulated arc therapy (VMAT) treatment plans were evaluated: with coplanar arcs (Eclipse®, Varian, VMATc_Eclipse®), with coplanar and non-coplanar arcs (VMATnc_Eclipse®), and with non-coplanar arcs (Elements Cranial SRS®, Brainlab, VMATnc_Elements®). The marginal dose prescribed for the PTV was 23.1Gy (isodose 70%) in three fractions. The mean GTV was 27mm³.

RESULTS

Better conformity indices were found with all VMAT techniques compared to DCA (1.05 vs 1.28, P<0.05). Better gradient indices were found with VMATnc_Elements® and DCA (2.43 vs 3.02, P<0.001). High-dose delivery in healthy brain was lower with all VMAT techniques compared to DCA (5.6 to 6.3 cc vs 9.4 cc, P<0.001). Low-dose delivery (V5Gy) was lower with VMATnc_Eclipse® or VMATnc_Elements® than with DCA (81 or 94 cc vs 110 cc, P=0.02).

CONCLUSIONS

NovalisTx® VMAT HFSRT for≥25mm diameter brain metastases provides the best dosimetric compromise in terms of target coverage, sparing of healthy brain tissue and low-dose delivery compared to DCA.

Dosimetric quality and delivery efficiency of robotic radiosurgery for brain metastases: Comparison with C-arm linear accelerator based plans

The incidence of brain metastases is increasing and various treatment modalities exist for brain metastases. The aim of this study was to investigate the dosimetric quality and delivery efficiency of robotic radiosurgery (CyberKnife) for multiple brain metastases compared with C‐arm linear accelerator (linac) based plans. C‐arm linac based plans included intensity‐modulated radiation therapy (IMRT), volumetric modulated arc therapy (VMAT) and non‐coplanar VMAT with 1, 3 and 5 non‐coplanar arcs, respectively (NC1, NC3 and NC5). For 20 patients, six plans with a prescription dose of 30 Gy in three fractions were generated. The gradient index (GI), conformity index (CI), maximum dose (D_max) of organs at risk (OARs), normal brain tissue volume (V_3 Gy–V_24 Gy), monitor units (MUs) and beam on time (BT) were evaluated. The GI of CyberKnife plans (3.60 ± 0.70) was lower than IMRT (6.21 ± 2.26, P < 0.05), VMAT (6.04 ± 1.93, P < 0.05), NC1 (5.16 ± 1.71, P < 0.05), NC3 (5.02 ± 1.59, P < 0.05) and NC5 (5.03 ± 1.72, P < 0.05). The CI of the VMAT plans (both coplanar and non‐coplanar) was larger than IMRT and CK plans. The D_max for most OARs of the CyberKnife plan was lower than the C‐arm linac based plans, although some differences were not statistically significant. The normal brain tissue volume of CyberKnife plan was lower than the C‐arm linac based plans, and the normal brain tissue volume of non‐coplanar VMAT plans was lower than IMRT and VMAT plans at high‐moderate dose level. However, the MUs and BT of CyberKnife plans was more than C‐arm linac based plans. CyberKnife plan was better than C‐arm linac based plans in protecting normal brain tissue and OARs for patients with multiple brain metastases. C‐arm linac based plan with non‐coplanar arc provided better protection of normal brain tissue than coplanar plan. However, the BT of CyberKnife plan was longer than C‐arm linac based plans.

Dosimetric and Radiobiological Comparison of External Beam Radiotherapy Using Simultaneous Integrated Boost Technique for Esophageal Cancer in Different Location

Objectives: To compare treatment plans of intensity modulated radiotherapy (IMRT), volumetric modulated arc radiotherapy (VMAT), and helical tomotherapy (HT) with simultaneous integrated boost (SIB) technique for esophageal cancer (EC) of different locations using dosimetry and radiobiology. Methods: Forty EC patients were planned for IMRT, VMAT, and HT plans, including 10 cases located in the cervix, upper, middle, and lower thorax, respectively. Dose-volume metrics, conformity index (CI), homogeneity index (HI), tumor control probability (TCP), and normal tissue complication probability (NTCP) were analyzed to evaluate treatment plans. Results: HT showed significant improvement over IMRT and VMAT in terms of CI (p = 0.007), HI (p < 0.001), and TCP (p < 0.001) in cervical EC. IMRT yielded more superior CI, HI and TCP compared with VMAT and HT in upper and middle thoracic EC (all p < 0.05). Additionally, V30 (27.72 ± 8.67%), mean dose (1801.47 ± 989.58cGy), and NTCP (Niemierko model: 0.44 ± 0.55%; Lyman-Kutcher-Burman model: 0.61 ± 0.59%) of heart in IMRT were sharply reduced than VMAT and HT in middle thoracic EC. For lower thoracic EC, the three techniques offered similar CI and HI (all p > 0.05). But VMAT dramatically lowered liver V30 (9.97 ± 2.84%), and reduced NTCP of lungs (Niemierko model: 0.47 ± 0.48%; Lyman-Kutcher-Burman model: 1.41 ± 1.07%) and liver (Niemierko model: 0.10 ± 0.08%; Lyman-Kutcher-Burman model: 0.17 ± 0.17%). Conclusions: HT was a good option for cervical EC with complex target coverage but little lungs and heart involvement as it achieved superior dose conformity and uniformity. Due to potentially improving tumor control and reducing heart dose with acceptable lungs sparing, IMRT was a preferred choice for upper and middle thoracic EC with large lungs involvement. VMAT could ameliorate therapeutic ratio and lower lungs and liver toxicity, which was beneficial for lower thoracic EC with little thoracic involvement but being closer to heart and liver. Individually choosing optimal technique for EC in different location will be warranted.

Dosimetric characterization of hypofractionated Gamma Knife radiosurgery of large or complex brain tumors versus linear accelerator-based treatments

OBJECTIVE Noninvasive Gamma Knife (GK) platforms, such as the relocatable frame and on-board imaging, have enabled hypofractionated GK radiosurgery of large or complex brain lesions. This study aimed to characterize the dosimetric quality of such treatments against linear accelerator-based delivery systems that include the CyberKnife (CK) and volumetric modulated arc therapy (VMAT). METHODS Ten patients treated with VMAT at the authors' institution for large brain tumors (> 3 cm in maximum diameter) were selected for the study. The median prescription dose was 25 Gy (range 20-30 Gy) in 5 fractions. The median planning target volume (PTV) was 9.57 cm³ (range 1.94-24.81 cm³). Treatment planning was performed using Eclipse External Beam Planning V11 for VMAT on the Varian TrueBeam system, Multiplan V4.5 for the CyberKnife VSI System, and Leksell GammaPlan V10.2 for the Gamma Knife Perfexion system. The percentage of the PTV receiving at least the prescription dose was normalized to be identical across all platforms for individual cases. The prescription isodose value for the PTV, conformity index, Paddick gradient index, mean and maximum doses for organs at risk, and normal brain dose at variable isodose volumes ranging from the 5-Gy isodose volume (V5) to the 15-Gy isodose volume (V15) were compared for all of the cases. RESULTS The mean Paddick gradient index was 2.6 ± 0.2, 3.2 ± 0.5, and 4.3 ± 1.0 for GK, CK, and VMAT, respectively (p < 0.002). The mean V15 was 7.5 ± 3.7 cm³ (range 1.53-13.29 cm³), 9.8 ± 5.5 cm³ (range 2.07-18.45 cm³), and 16.1 ± 10.6 cm³ (range 3.58-36.53 cm³) for GK, CK, and VMAT, respectively (p ≤ 0.03, paired 2-tailed t-tests). However, the average conformity index was 1.18, 1.12, and 1.21 for GK, CK, and VMAT, respectively (p > 0.06). The average prescription isodose values were 52% (range 47%-69%), 60% (range 46%-68%), and 88% (range 70%-94%) for GK, CK, and VMAT, respectively, thus producing significant variations in dose hot spots among the 3 platforms. Furthermore, the mean V5 values for GK and CK were similar (p > 0.79) at 71.9 ± 36.2 cm³ and 73.3 ± 31.8 cm³, respectively, both of which were statistically lower (p < 0.01) than the mean V5 value of 124.6 ± 67.1 cm³ for VMAT. CONCLUSIONS Significantly better near-target normal brain sparing was noted for hypofractionated GK radiosurgery versus linear accelerator-based treatments. Such a result supports the use of a large number of isocenters or confocal beams for the benefit of normal tissue sparing in hypofractionated brain radiosurgery.

Treatment of brain oligometastases with hypofractionated stereotactic radiotherapy utilising volumetric modulated arc therapy

Stereotactic radiosurgery (SRS) is commonly used to treat brain metastases, particularly in the oligometastatic setting. This study analyses our initial experience in treating oligometastatic brain disease using Volumetric Modulated Arc Therapy (VMAT) to deliver hypofractionated stereotactic radiotherapy (HFSRT). Sixty-one patients were treated with HFSRT with a median dose of 24 Gy (range 22-40 Gy) in a median of three fractions (range 2-10 fractions). With a median follow-up of 23 months, the local control rate was 74 % for the entire cohort. Local control was 87 % for patients who had surgery with no radiological evidence of residual disease followed by HFSRT compared with 69 % in patients treated with HFSRT alone. The overall median time post radiotherapy to local failure was 8.6 months and to extracranial failure was 7.9 months. The mean time to distant brain failure was 9.9 months. Twenty-two patients (36 %) died during the study with median time to death of 4.4 months. Median overall survival (OS) from treatment was 21 months and 12 month OS was 60 %. Our experience with HFSRT using VMAT for oligometastatic brain metastases in the post-operative setting demonstrates comparable local control and survival rates compared with international published data. In the intact brain metastasis setting, local control using the dose levels and delivery in this cohort may be inferior to radio-surgical series. Local control is independent of histology. Careful selection of patients remains critical.

On the cutting edge of intensity modulated radiotherapy and simultaneous integrated boost (IMRT-SIB): The case of a patient with 8 brain metastases

BACKGROUND

Patients with multiple brain metastases, especially those with more than 3 lesions, usually undergo to palliative whole brain (WB) radiotherapy (RT).

METHODS

A breast cancer patient with 8 brain metastases was treated on the brain by a radical RT regimen. Prescription doses were according to the simultaneous integrated boost-intensity modulated radiation therapy (SIB-IMRT) technique with all lesions as well brain irradiated simultaneously in 20 daily fractions. Doses of 40.0 Gy (2.0 Gy/fraction) and 50.0 Gy (2.5 Gy/fraction) were prescribed to the whole brain and to eight individual metastases, respectively.

RESULTS

Mean volume of the eight metastases was 8.1 cc (range: 3.8-10.1 cc). For all lesions, the volume receiving 95% of prescribed dose was 100% and dose homogeneity was within 3%. Moreover, maximum doses were less than 105% of prescribed dose, while average mean dose to lesions was 50.6 Gy (range: 49.7-51.5 Gy). Whole brain mean dose was 45.2 Gy. Maximum doses to brainstem and optic chiasma were limited to 44.5 Gy and 42.9 Gy, respectively, while maximum doses to eyes, lens and optic nerves were limited to 9.2 Gy, 4.9 Gy and 41.0 Gy, respectively. From a clinical point of view, subsequent MRI brain controls showed a complete clinical response. Forty months after treatment the patient is disease free and shows no late brain and skin toxicities.

CONCLUSION

This case demonstrates the technical feasibility of a SIB-IMRT treatment in patients with more than 3 brain metastases.

Stereotactic radiosurgery (SRS) with volumetric modulated arc therapy (VMAT): interim results of a multi-arm phase I trial (DESTROY-2)

AIMS

To present the interim results of a phase I trial on stereotactic radiosurgery (SRS) delivered using volumetric modulated arc therapy (VMAT) in patients with primary or metastatic tumours in different extracranial sites.

MATERIALS AND METHODS

Patients were enrolled in different arms according to tumour site and clinical stage, and sequentially assigned to a given dose level. Acute toxicity, tumour response and early local control were investigated and reported.

RESULTS

One hundred lesions in 65 consecutive patients (male/female: 30/35, median age: 66 years; range: 40-89) were treated. Of these 100 lesions, 21 were primary or metastatic lung tumours, 24 were liver metastases, 30 were bone metastases, 24 were nodal metastases and one was a primary vulvar melanoma. The prescribed dose ranged from 12 (BED(2Gy,α/β:10) = 26.4 Gy) to 28 Gy (BED(2Gy,α/β:10) = 106.4 Gy) to the planning target volume. Twenty-one patients (32.3%) experienced grade 1-2 acute toxicity, which was grade 2 in only two cases. The overall response rate based on computed tomography/magnetic resonance imaging was 52% (95% confidence interval 40.1-63.2%) and based on positron emission tomography scan was 90% (95% confidence interval 76.2-96.4%). As of November 2013, the median duration of follow-up was 11 months (range = 1-38). Recurrence/progression within the SRS-VMAT treated field was observed in nine patients (total lesions = 18): the inside SRS-VMAT field local control expressed on a per lesion basis was 87.8% at 12 months and 71.9% at 24 months.

CONCLUSIONS

The maximum tolerable dose has not yet been reached in any study arm. SRS-VMAT resulted in positive early clinical results in terms of tumour response, local control rate and acute toxicity.

Geometric and dosimetric uncertainties in intracranial stereotatctic treatments for multiple nonisocentric lesions

The purpose of this study was to determine the effects of geometric uncertainties of patient position on treatments of multiple nonisocentric intracranial lesions. The average distance between lesions in patients with multiple targets was determined by a retrospective survey of patients with multiple lesions. Retrospective patient imaging data from fractionated stereotactic patients were used to calculate interfractional and intrafractional patient position uncertainty. Three different immobilization devices were included in the positioning study. The interfractional and intrafractional patient positioning error data were used to calculate the geometric offset of a lesion located at varying distances from the mechanical isocenter for treatments of multiple lesions with a single arc, assuming that no intrafractional position correction is employed during an arc rotation. Dosimetric effects were studied using two representative lesions of two sizes, 6 mm and 13 mm maximum dimensions, and prescribed to 20 Gy and 18 Gy, respectively. Distances between lesions ranged from < 10 mm to 150 mm, which would correspond to a range of isocenter to lesion separations of < 10 mm to 75 mm, assuming an isocenter located at the geometric mean. In the presence of a full six degree of freedom patient correction system, the effects of the intrafractional patient positioning uncertainties were less than 1.8 mm (3.6 mm) for 1σ (2σ) deviations for lesion spacing up to 75 mm assuming a quadratic summation of 1σ and 2σ. Without the benefit of a six DOF correction device, only correcting for three translations, the effects of the intrafractional patient positioning uncertainties were within 3.1 mm (7.2 mm) for 1σ (2σ) deviations for distances up to 75 mm. 1σ and 2σ deviations along all six axes were observed in 3.6% and 0.3%, respectively, of 974 fractions analyzed. Dosimetric effects for 2 mm and 4 mm offsets were most significant for the small lesion with minimum dose (Dmin) decreasing from 20 Gy to 13.6 Gy and 5.7 Gy and volume receiving the prescription (V_20Gy) reducing from 100% to 57% and 16%, respectively. The dosimetric effects on the larger lesion were less pronounced with Dmin reducing from 18 Gy to 17.5 Gy and 14.2 Gy, and V_18Gy reducing from 100% to 98.3% and 85.4%, for 2 mm and 4 mm offsets, respectively. In the 1σ scenario (3.6% of patients) angular uncertainties in patient positioning can introduce 1.0 mm shifts in the location of the lesion position at distances of 75 mm, compared to an isocentric treatment even with a full six DOF correction. Without the ability to correct angular positioning errors, a lesion positioned 75 mm away from the mechanical isocenter can be located in 3.6% of patients > 3.0 mm distant from the planned position. Dosimetric results depend upon the distance from isocenter and the size of the target. Single isocenter treatments for multiple lesions should be considered only when full six DOF corrections can be applied, the intrafractional immobilization precision is well quantified, and a PTV expansion is included for more distant lesions to account for unavoidable residual patient positioning uncertainties.

PACS number: 87.55.Qr, 87.53.Ly, 87.55.D‐

Extracranial radiosurgery with volumetric modulated arc therapy: Feasibility evaluation of a phase I trial

The aim of this study was to report early clinical experience in stereotactic body radiosurgery (SBRS) delivered using volumetric intensity modulated arc therapy (VMAT) in patients with primary or metastatic tumors in various extra-cranial body sites. Each enrolled subject was included in a different phase I study arm, depending on the tumor site and the disease stage (lung, liver, bone, metastatic), and sequentially assigned to a particular dose level. Technical feasibility and dosimetric results were investigated. The acute toxicity, tumor response and early local control were also studied. In total, 25 lesions in 20 consecutive patients (male/female, 11/9; median age, 67 years; age range, 47-86 years) were treated. Of these 25 lesions, 4 were primary or metastatic lung tumors, 6 were liver metastases, 8 were bone metastases and 7 were nodal metastases. The dose-volume constraints for organs at risk (OARs) were observed in 19 patients using a single-arc technique. Only in one patient were two arcs required. The treatment was performed without interruption or any other technical issues. The prescribed dose ranged from 12-26 Gy to the planning target volume (PTV). Delivery time ranged from 4 min to 9 min and 13 sec (median, 6 min and 6 sec). No incidence of grade 2-4 acute toxicity was recorded. The overall response rate was 48% (95% confidence interval (CI), 24.2-70.2) based on computed tomography (CT)/magnetic resonance imaging (MRI) and 89% (95% CI, 58.6-98.7) based on the positron emission tomography (PET) scan. SBRS delivered by means of VMAT allowed the required target coverage to be achieved while remaining within the normal tissue dose-volume constraints in the 20 consecutive patients. VMAT-SBRS resulted in adequate technical feasibility; the maximum tolerable dose has not yet been reached in any study arm.

Volumetric modulated arc therapy: a review of current literature and clinical use in practice

Volumetric modulated arc therapy (VMAT) is a novel radiation technique, which can achieve highly conformal dose distributions with improved target volume coverage and sparing of normal tissues compared with conventional radiotherapy techniques. VMAT also has the potential to offer additional advantages, such as reduced treatment delivery time compared with conventional static field intensity modulated radiotherapy (IMRT). The clinical worldwide use of VMAT is increasing significantly. Currently the majority of published data on VMAT are limited to planning and feasibility studies, although there is emerging clinical outcome data in several tumour sites. This article aims to discuss the current use of VMAT techniques in practice and review the available data from planning and clinical outcome studies in various tumour sites including prostate, pelvis (lower gastrointestinal, gynaecological), head and neck, thoracic, central nervous system, breast and other tumour sites.