Room: ePoster Forums
Purpose: Dynamic conformal arc therapy (DCAT) using multiple isocenters has been used as an alternative to whole-brain radiation therapy to treat multiple brain metastases in the past. Starting in 2010, Duke University Medical Center has gradually switched to a single-isocenter technique to treat these patients using volumetric modulated arc therapy (VMAT) on Eclipse version 13.6. The purpose of this project is to create a single-isocenter plan using DCAT, previously used with multiple isocenters, to compare with the current standard of care at Duke University Medical Center: single-isocenter VMAT. We want to determine if a potential multiple brain mets patient could benefit more from DCAT instead of VMAT, which is currently used for all multiple brain mets patients at Duke University Medical Center.
Methods: Single-isocenter DCAT plans were created for 40 multiple brain mets patients who received single-isocenter VMAT at Duke University Medical Center from 2016 to 2018, randomly selected based only on number of metastases, from 2 to 14. DCAT plans were created using protocols with 5 couch positions, a 4Â° minimum collimator angle, and 100Â° arcs on BrainLab Elementsâ€™ Multiple Brain Mets SRS version 1.5. For comparison, we determined the conformity index, gradient index, V3Gy, and V5Gy from each plan.
Results: The previously delivered VMAT plans had an average conformity index of 1.47 and gradient index of 8.57. Average whole-brain V3Gy and V5Gy were 14.07% and 5.80%, respectively. In comparison, using DCAT the conformity index was 1.75 and the gradient index was 6.87. Whole-brain V3Gy and V5Gy were 11.25% and 5.59%, respectively.
Conclusion: Overall, VMAT plans had higher conformity indexes with lower gradient indexes at the cost of healthy brain protection compared to DCAT. Patients in need of lower whole-brain doses may benefit from DCAT, but results are case-by-case.