Comparison of deliverable IMRT and VMAT for spine metastases using a simultaneous integrated boost

Abstract

Objective: To effectively treat spine metastases, significant dose must be delivered to regions surrounding the spinal cord. We present a study comparing both step-and-shoot intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) techniques to deliver a concomitant hypofractionated prescription dose to the diseased region and to the involved vertebrae.Methods: Seven-field IMRT and a single arc VMAT were inversely planned on five (two cervical and three thoracic) spinal metastatic patients. Planning target volumes PTVm (macroscopic) and PTVe (elective involved vertebrae) and associated organs at risk were localised. Mean doses of 35 Gy to PTVm and 20 Gy to PTVe were prescribed in five fractions. Dose statistics, estimated delivery time and results of verification using Delta 4 (ScandiDos, Uppsala, Sweden) were compared.Results: Deliverable plans were achieved with both IMRT and VMAT. The coverage to PTV was similar for both IMRT and VMAT (p50.5) and the dose to the regions adjacent to the spinal cord was 1% higher with VMAT (p50.04). The mean delivery time for VMAT was 3.5min compared with 10.5min for IMRT. Fewer monitor units were required to deliver IMRT than to deliver VMAT. The median (range) percentage of measured points with a g-index ,1 with 3%/3 mm was 100 (99.9-100)% for IMRT and 100 (88.5-100)% for VMAT.Conclusion: Both VMAT and IMRT can deliver the concomitant hypofractionated regime proposed, and both offer different benefits in dose delivery. IMRT is currently preferred for its superior pre-treatment verification results and shorter planning times. Advances in knowledge:This study explores the feasibility of delivering tumouricidal doses of radiation to metastatic spine disease in the vicinity of the spinal cord.

Use of Imaging in the Management of Metastatic Spine Disease With Percutaneous Ablation and Vertebral Augmentation

“…We strive to ablate the entire volume of T2 and STIR hyperintensity and enhancement on MRI, including an additional 3-mm margin to account for microscopic tumor spread [36]. In many cases, the abnormal signal intensity on MRI extends beyond the margins of osteolysis or sclerosis evident on CT images (Fig.…”

Treatment planning of VMAT and step‐and‐shoot IMRT delivery techniques for single fraction spine SBRT: An intercomparative dosimetric analysis and phantom‐based quality assurance measurements

“…When comparing ssIMRT and VMAT for spine SBRT, previous studies have used research replans . While it is important to keep the same anatomy, research replans are different from clinical plans; research replans are not planned under the same clinical stress (limited time/resources) and do not undergo the scrutiny of treating radiation oncologists.…”

Plan averaging for multicriteria navigation of sliding window IMRT and VMAT

“…State-ofthe-art optimization of VMAT plans lags behind that of static beam IMRT. [9][10][11] Also, it is less obvious at the outset that the technique described will work in the VMAT setting, whereas for static beam delivery, our trajectory averaging technique results in exact fluence map and dose averaging.…”