Work

Transmission beam planning for improved robustness and efficiency in proton therapy for head and neck cancer

Year: 2025

Type: article

Abstract: Background and purpose: Optimizing head and neck cancer (HNC) plans with single-energy proton beams that fully traverse the patient (transmission beams) can improve robustness and delivery efficiency, complementing conventional approaches. Materials and Methods: Experimental measurements, validated with Monte Carlo (MC) simulations, were carried out on a uniform water-equivalent plastic phantom (RW3) containing a metal component (2-Euro coins) irradiated with a single high energy proton field (228.6 MeV) to verify the transmission beam concept. 28 nasopharyngeal cancer (NPC) intensity modulated proton therapy (IMPT) were then optimized with nine coplanar single-energy fields (228.6 MeV), positioning the Bragg peaks well beyond the patient body, so called transmission beam mode. These plans (IMPT-TB) were compared to conventional IMPT and volumetric modulated arc therapy (VMAT) photon plans in terms of dose distributions quality, expected organ at risk (OAR) toxicity, robustness and delivery time. Results: Transmission beams minimized dose perturbation by metal objects (∼7% max relative variation at 18 cm depth). IMPT-TB plans achieved comparable dose distribution and expected toxicities to IMPT, increasing the dose bath (+96 % vs. IMPT) but remaining significantly lower than VMAT (-31.4 %). For 94 % of patients (N = 26), IMPT-TB met at least one additional dose constraint that the corresponding IMPT plan failed to satisfy. Moreover, in the analyzed subgroup (N = 5), IMPT-TB plans delivered with our synchrotron exhibit a 67 % reduction in beam time compared to IMPT plans. Conclusions: IMPT-TB plans demonstrated enhanced robustness and significantly faster delivery compared to IMPT. Transmission beams could be clinically implemented, also in conjunction with standard IMPT, for proton radiation treatment of NPC.

Source: Physics and Imaging in Radiation Oncology

DOI: 10.1016/j.phro.2025.100777