Practical radiation oncology | 2019
Assessing Functionality and Benefits of Comprehensive Dose Volume Prescriptions: An International, Multi-Institutional, Treatment Planning Study in Spine Stereotactic Body Radiation Therapy.
Abstract
PURPOSE\nThis study aimed to assess the effectiveness of multiple dose-volume specifications in minimizing interinstitutional, target-prescribed, dose variations for spine stereotactic body radiation therapy (SBRT).\n\n\nMETHODS AND MATERIALS\nSeven institutions with a total of 10 treatment apparatuses participated in this study. SBRT plans for 3 representative spinal metastases were generated using 2 different protocols (Protocols 1 and 2) for target dose. While using just 2 target dose objectives (doses delivered to 95% and maximum point dose) in Protocol 1, 3 target dose constraints (doses delivered to 95% and 50% and maximum point dose) were defined in Protocol 2 with the intent to decrease target dose variation. A dose-volume histogram analysis was performed for the evaluated planning target volume (PTVevl) and critical neural structures such as the spinal cord and cauda equina.\n\n\nRESULTS\nDoses to the organs at risk were all maintained at the maximal tolerance in both protocols; however, the interinstitutional variation of the PTVevl dose-volume histograms was significantly decreased with Protocol 2. Furthermore, the mean PTVevl covered by the prescription dose was increased from 73.0% in Protocol 1 to 85.8% in Protocol 2. There were no differences in the mean values of the nearly maximum dose of the critical neural structures between 2 protocols.\n\n\nCONCLUSIONS\nIn spine SBRT with the emphasis on preservation of critical neural structures, the target prescribed dose should be defined by using multiple dose-volume objectives to minimize user and apparatus-dependent dose variabilities for the spinal metastases that are adjacent to the critical neural structures.