Incorporating Variable RBE in IMPT Optimization for Ependymoma

Authors

Hadis Moazami Goudarzi
Gino Lim
David Grosshans
Radhe Mohan
Wenhua Cao

Publication Date

1-1-2024

Journal

Journal of Applied Clinical Medical Physics

Abstract

PURPOSE: To study the dosimetric impact of incorporating variable relative biological effectiveness (RBE) of protons in optimizing intensity-modulated proton therapy (IMPT) treatment plans and to compare it with conventional constant RBE optimization and linear energy transfer (LET)-based optimization.

METHODS: This study included 10 pediatric ependymoma patients with challenging anatomical features for treatment planning. Four plans were generated for each patient according to different optimization strategies: (1) constant RBE optimization (ConstRBEopt) considering standard-of-care dose requirements; (2) LET optimization (LETopt) using a composite cost function simultaneously optimizing dose-averaged LET (LET

RESULTS: We found that the LETopt plans consistently achieved increased LET in tumor targets and similar or decreased LET in critical organs compared to other plans. On average, the VarRBEopt plans achieved lower mean and maximum doses with both constant and variable RBE in the brainstem and spinal cord for all 10 patients. To compensate for the underdosing of targets with 1.1 RBE for the VarRBEopt plans, the hRBEopt plans achieved higher physical dose in targets and reduced mean and especially maximum variable RBE doses compared to the ConstRBEopt and LETopt plans.

CONCLUSION: We demonstrated the feasibility of directly incorporating variable RBE models in IMPT optimization. A hybrid RBE optimization strategy showed potential for clinical implementation by maintaining all current dose limits and reducing the incidence of high RBE in critical normal tissues in ependymoma patients.

Keywords

Child, Humans, Proton Therapy, Radiotherapy Dosage, Relative Biological Effectiveness, Linear Energy Transfer, Ependymoma, Radiotherapy Planning, Computer-Assisted, Organs at Risk, ependymoma, IMPT, LET, optimization, RBE

Comments

PMID: 37985962