Reproducibility of Deep-Inspiration Breath Hold treatments on Halcyon (TM) performed using the first clinical version of AlignRT InBore (TM): Results of CYBORE study

Background and purpose: To investigate the reproducibility of deep-inspiration breath hold (DIBH) breast cancer treatments on Halcyon (TM) performed using the first clinical version of AlignRT InBore (TM) (Vision RT Ltd., London, UK), a Halcyon's SGRT dedicated solution. Materials and methods: The ease and feasibility of DIBH treatments was retrospectively investigated for the initial 22 left breast cancer patients treated on Halcyon (TM) using AlignRT InBore (TM). Setup time, Cone beam computed tomography (CBCT) imaging and analysis time as well as overall treatment time were recorded. Online and offline review of CBCT images was undertaken to verify the compliance of breast, heart, spine, sternum and diaphragmatic domes positions. Results: Mean duration of patient setup, CBCT analysis and overall treatment time were 4 min, 1.1 min and 14 min respectively. Online review of 520 CBCT acquisitions by therapists showed minimal positioning shifts with AlignRT InBore (TM) guidance with mean value of vertical, longitudinal, and lateral shifts of 1.7 mm, -1.7 mm, and -0.2 mm respectively. Meanwhile, offline review of 115 CBCTs by the radiation oncologist, showed reproducible breath hold (BH) with average deviation of breast, heart, spine, sternum and diaphragmatic domes respectively within 2.4 mm, 2.9 mm, 3.3 mm, 3.2 mm and 4.5 mm in magnitude. Conclusion: AlignRT InBore (TM) allows for accurate and reproducible DIBH on Halcyon (TM) with breast and heart organs' positions within 3 mm in magnitude of expected position and fully compliant with planning margins (5 mm anisotropic CTV-PTV margins).