Custom knowledge-based planning method to escalate tumor dose for stereotactic recurrent head and neck cancer with HyperArc delivery

Demonstrating the feasibility of dose escalation for stereotactic recurrent head and neck (RHN) cancers with a HyperArc-based RapidPlan (HARP) model using custom Simultaneous Integrated Boost Injector (SIBI) through Eclipse Scripting API (ESAPI) to facilitate automated treatment planning. Five previously treated RHN patients prescribed 30 to 35 Gy in 3 or 5 fractions, four single-lesion and one two-lesion, were retrospectively replanned with HyperArc geometry on a TrueBeam LINAC (6MV-FFF) using a HARP model with SIBI to escalate tumor dose. Escalation was achieved through the GTV and a central hotspot optimization structure being pushed toward 130% and 140% the prescription dose, respectively. To accommodate this escalation, PTV coverage objectives were lessened. After dose calculation using AcurosXB, the stereotactic plan was normalized to the original plan’s PTV D _95%. On average, the mean dose to the PTVs and GTVs received an 11.5% ± 5.1% and 25.0% ± 8.7% increase. Maximum GTV dose increased by 39.5% ± 10.2% and GTV D _99.9% increased by 16.4% ± 5.4%. Maximum dose to organs-at-risk (OARs) showed notable decreases for larynx (8.6 Gy), oral cavity (11.4 Gy), spinal cord (12.6 Gy), and parotids (11.4 Gy) for specific cases. Skin and brainstem saw maximum increases of 4.9 Gy and 3.4 Gy, respectively. Carotid artery dose was respected for all RHN plans, including plans with target overlap. All SIB plans were calculated automatically without user intervention in under 15 minutes on average. Patient-specific quality assurance results were clinically acceptable for RHN stereotactic radiotherapy delivery. Achieving an escalated stereotactic RHN dose without compromising nearby OARs has the potential to improve clinical outcomes through a possible increase in tumor local control while maintaining acceptable doses to OARs. Furthermore, the involvement of HyperArc, RapidPlan, and ESAPI allows for a standardized and streamlined clinical workflow, enabling resource-strained centers to deliver high-quality stereotactic RHN treatments without requiring extensive experience or time for manual planning.