Author: Shane McCarthy, Damodar Pokhrel, William St. Clair, Eddy S Yang 👨🔬
Affiliation: University of Kentucky, Department of Radiation Medicine 🌍
Purpose: Demonstrating the feasibility of dose escalation for stereotactic recurrent head and neck (RHN) cancers through the deployment of a Hyper-Arc Based RapidPlan (HARP) model through an Eclipse Scripting API (ESAPI) script to allow automated custom target optimization objective injection.
Methods: Five previously treated RHN patients prescribed 30-35 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 custom objective injection to escalate tumor dose. Escalation was facilitated through the GTV and a central hotspot optimization structure being pushed towards 130% and 140% the prescription dose, respectively. To accommodate this escalation, PTV coverage objectives were modified. After dose calculation using AcurosXB, the stereotactic plan was normalized to the original plan’s PTV D95%.
Results: On average, the mean dose to the PTVs and GTVs received a 11.5% ± 5.1% and 25.0% ± 8.7% increase. Maximum GTV dose increased by 39.5% ± 10.2% and GTV D99.9% increased by 16.4% ± 5.4%. Maximum dose to 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 plans were calculated automatically without user intervention in 14.4 ± 3.3 minutes.
Conclusion: 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 without a higher risk of radionecrosis. 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 radiation treatments without requiring extensive experience or time for planning.