S Mein*, B Kopp, T Tessonnier, J Liermann, S Harrabi, J Debus, C Schoemers, A Abdollahi, T Haberer, A Mairani,

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  S Mein

SU-J-206-4 (Sunday, 7/10/2022) 4:00 PM - 5:00 PM [Eastern Time (GMT-4)]

Room 206

Purpose: To develop and evaluate spot-scanning hadron arc (SHArc) therapy, the first arc delivery technique for light and heavy ions. Single and multi-ion optimization strategies were investigated using protons (p), helium (⁴He), carbon (¹²C), oxygen (¹⁶O) and/or neon (²⁰Ne) ion beams.

Methods: SHArc treatment design and optimization procedures were developed for efficient and robust delivery (Fig 1a). SHArc treatments were optimized and surveyed for various clinical indications using single (p, ⁴He, ¹²C, ¹⁶O, or ²⁰Ne) and multi-ion (¹²C+⁴He, ¹⁶O+⁴He or ²⁰Ne+⁴He) strategies: glioblastoma, skull-base chordoma, prostate carcinoma pancreatic adenocarcinoma, and non-small cell lung carcinoma. Dosimetric and biophysical features were evaluated against reference clinical plans using photon and particle therapy, i.e., volumetric modulated arc therapy (VMAT) and intensity modulated particle therapy (IMPT). A model for hypoxia-induced radio-resistance was developed and applied to investigate impact of LET on effective dose. Treatment times for step-and-shoot delivery were estimated.

Results: SHArc plans exhibited a low-dose bath outside the target volume with a reduced maximum dose in normal tissues compared to single and multi-field plans. Compared to VMAT, SHArc planning substantial reduced mean dose in normal tissue (∆≈40-70%). Substantial increases in min and max LET in the GTV were possible with SHArc compared to IMPT, indicating a potential means for mitigating tumor radio-resistance using LET enhancement with ¹²C, ¹⁶O, or ²⁰Ne ions. Multi-ion arc plans achieved similar distributions with highly homogenous physical dose and RBE in the target volume (Fig 1b). Estimated delivery times for SHArc ranged from 8 to 15 minutes.

Conclusion: The first arc treatment delivery technique for light and heavy ions beams is proposed. Evidence suggests that through arc delivery of high-LET particle beams, SHArc and multi-ion therapy may offer unique clinical benefits. SHArc treatments may improve local control by mitigating impact of radio-resistance factors such as tumor hypoxia.

Keywords

Heavy Ions, LET, RBE

Taxonomy

TH- External Beam- Particle/high LET therapy: Other particle therapy

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