Development and Validation of In-House Automatic VMAT Planning for Single Fraction and 5-Fraction Partial Breast Irradiation
Abstract
Purpose
To describe the development and validation of in-house automatic planning for VMAT partial breast irradiation (PBI) in either 1 or 5 fractions.
Methods
The Treatment Planning Automation System (TPAS) is an in-house platform that enables VMAT plans to be produced in Eclipse with automatic priority adjustments and iterative re-optimization if planning goals are not met. For this study, TPAS protocols were developed for 26 Gy in 5 fractions and 13 Gy in 1 fraction VMAT PBI using planning goals from the upcoming SHIFT-PB phase II clinical trial (ClinicalTrials.gov ID NCT06885671). Forty-nine clinical 5-fraction plans were replanned with TPAS for both 5 and 1 fraction treatments and compared via PTV and OAR planning goals, 95% and 50% conformity indices (CI), PTV homogeneity index (HI), and monitor units (MU). Time from TPAS plan submission to completion and number of iterative optimizations per plan were recorded.
Results
All TPAS plans achieved all planning goals for PTVs, lungs, heart, and uninvolved ipsilateral breast. Compared to manually planned 5-fraction plans, TPAS 5-fraction plans had significantly lower median heart V1.5Gy and V3Gy (p<0.001 for both), contralateral breast D0.035cc (p<0.001), 95% and 50% CI (p<0.001 for both) but higher median HI (p=0.004) and MU (p<0.001). 40 of 49 5-fraction and 36 of 49 1-fraction TPAS plans completed in a single optimization. The remainder underwent automated priority adjustments and iterative re-optimization, with a median (range) number of optimizations of 2 (2-9) for both 5 and 1-fraction plans. The median (range) time from TPAS plan submission to completion was 9.0 min (7.0-24.3 min) for 5-fraction and 8.7 min (6.3-20.8 min) for 1-fraction plans.
Conclusion
In-house automation of VMAT PBI with TPAS for 5 or 1 fraction plans is feasible, efficient, and may reduce dose to OARs compared to manual planning.