(Saturday, 4/4/2020) [Mountain Time (GMT-6)]
Purpose: Spatially-fractionated radiotherapy (SFRT) treatment techniques produce high-dose peaks and low-dose valleys in an evenly interspaced pattern throughout targets, and has been historically utilized for large tumors with reported dramatic tumor response. Lattice is a modern 3D approach to SFRT that aims to create the dosimetric variation using small high-dose vertices inter-spaced with low dose vertices, and is best achieved with volumetric-modulated arc therapy (VMAT). This approach allows for spatially-restricted dose-escalation to stereotactic body radiation therapy (SBRT) doses and rapid dose fall-off within the tumor, and can harness the biological advantages of both Lattice SFRT and SBRT. The purpose of this study was to develop a systematic planning approach for Lattice SBRT and examine the dosimetric feasibility on a retrospective patient cohort.
Methods: A cohort of 12 patients, each with tumors = 10 cm in the axial dimension, was utilized in the IRB approved retrospective feasibility study. A lattice of evenly interspaced high-dose and low-dose spheres (1.5cm diameter) were manually placed within the GTV on the clinical CT simulation datasets with VMAT plans generated utilizing Eclipse 15.6 (Varian Medical Systems). The specified planning goals included coverage of 66.7Gy to the high-dose vertices and less than 28Gy (40% of high-dose prescription) within the low-dose vertices, treated in 5 fractions, with the PTV covered by a minimum of 20Gy. Dose objectives for OARs were taken from AAPM Task Group 101. Dosimetric and patient-specific quality assurance (QA) analysis were assessed by physicists prior to treatment following established clinical guidelines.
Results: The desired high- and low-dose variation was achieved for all patients, with all ROI objectives achieved.
Conclusion: A systematic planning procedure was developed to create safe and deliverable Lattice 3D SFRT plans. This is currently being evaluated in 2 clinical trials, one of which will be completing enrollment by February 2020.
Contact Email
