3447 - Using an Auto-Planned VMAT-TBI Technique for Myeloablative Autologous Hematopoietic Stem Cell Transplantation for Scleroderma (the STAT-2 Trial)
Presenter(s)
C. Hui1, I. O. Romero2, E. A. Simiele3, S. Arai4, S. M. Hiniker5, M. S. Binkley5, R. T. Hoppe5, and N. Kovalchuk6; 1University of California - Irvine, Irvine, CA, 2Stanford University School of Medicine, Palo Alto, CA, 3University of Alabama Birmingham School of Medicine, Birmingham, AL, 4Stanford University, Stanford, CA, 5Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA, 6Department of Radiation Oncology, Stanford University, Stanford, CA
Purpose/Objective(s): The STAT-2 trial mandates lung and kidney sparing to 25% of prescription dose and image guidance for kidney localization, posing challenges for institutions using conventional 2D TBI techniques. This study demonstrates implementation of an auto-planned VMAT-TBI technique to facilitate STAT-2 patient enrollment and improve dissemination of modern TBI.
Materials/Methods: Our institution clinically implemented and automated VMAT-TBI treatment planning, and adapted scripts to meet STAT-2 trial requirements. Three patients were treated with 3-isocenter VMAT plans in HFS position and 2-isocenter AP/PA plans in FFS position. A custom rotational platform facilitated patient orientation changes. CBCT provided image guidance for lung and kidney localization. Dosimetric indices for lung and kidneys were retrospectively reviewed for three patients. Point doses were recorded at the head, neck, shoulder, mid-mediastinum, lumbar spine, hip, knee, and ankle to confirm dose uniformity.
Results: For a prescription dose of 8 Gy in 4 fractions, the average point doses for lungs and kidneys were 1.9±0.2 Gy and 1.9±0.4Gy, respectively. Lungs eval and kidney Dmean were 2.6±0.1 Gy and 2.9±0.5 Gy, respectively. Eight anatomical dose points throughout the body met prescription criteria within ±10%consistent with trial constraint. The treatment was well tolerated with minor post-treatment toxicities (G1 diarrhea, G2 nausea, G1mucositis).
Conclusion: Average lung and kidney point dose constraints were achieved for the three patients. DVH dose metrics were achieved on average within 0.60 Gy for lungs eval and 0.90 Gy for kidney volumes. VMAT-TBI offers superior treatment delivery for scleroderma patients, eliminating the need for heavy physical blocks and complexity of kidney localization. Auto-planning scripts are freely available on GitHub for wider VMAT-TBI adoption.