Using an Auto-Planned VMAT-TBI Technique for Myeloablative Autologous Hematopoietic Stem Cell Transplantation for Scleroderma (The STAT-2 Trial)

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Abstract Objectives The STAT-2 trial mandates lung and kidney sparing to 25% of the prescription dose and image guidance for kidney localization, posing challenges for institutions using conventional two-dimensional (2D) Total body irradiation (TBI) techniques. This study demonstrates implementation of an auto-planned volumetric modulated arc therapy-total body irradiation (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 head-first supine position and 2-isocenter anteroposterior and posteroanterior plans in feet-first supine position. A custom rotational platform facilitated patient orientation changes. Cone-Beam Computed Tomography provided image guidance for lung and kidney localization. Dosimetric indices for lungs 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±0.4 Gy, respectively. Lungs_eval and kidney D mean were 2.6±0.1 Gy and 2.9±0.5 Gy, respectively. Eight anatomical dose points throughout the body met the prescription criteria within ±10% consistent with the trial constraint. The treatment was well tolerated with minor post-treatment toxicities (G1 diarrhea, G2 nausea, and G1 mucositis). Conclusions Average lung and kidney point dose constraints were achieved for the three patients. Dose–Volume Histogram 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.

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