Advanced External Beam Stereotactic Radiotherapy for Skull Base Reirradiation

Authors

He Wang
Fahed M Alsanea
Dong Joo Rhee
Xiaodong Zhang
Wei Liu
Jinzhong Yang
Zhifei Wen
Yao Zhao
Tyler D Williamson
Rachel A Hunter
Peter A Balter
Tina M Briere
Ronald X Zhu
Anna Lee
Amy C Moreno
Jay P Reddy
Adam S Garden
David I Rosenthal
Gary B Gunn
Jack Phan

Language

English

Publication Date

2-5-2025

Journal

Cancers

DOI

10.3390/cancers17030540

PMID

39941906

PMCID

PMC11817895

PubMedCentral® Posted Date

2-5-2025

PubMedCentral® Full Text Version

Post-print

Abstract

Background/objectives: Stereotactic body radiation therapy (SBRT) for skull base reirradiation is particularly challenging, as patients have already received substantial radiation doses to the region, and nearby normal organs may have approached their tolerance limit from prior treatments. In this study, we reviewed the characteristics and capabilities of four advanced external beam radiation delivery systems and four modern treatment planning systems and evaluated the treatment plan quality of each technique using skull base reirradiation patient cases.

Methods: SBRT plans were generated for sixteen skull base reirradiation patients using four modalities: the GK plan for the Elekta Leksell Gamma Knife Perfexion/ICON, the CyberKnife (CK) plan for the Accuray CyberKnife, the intensity-modulated proton therapy (IMPT) plan for the Hitachi ProBeat-FR proton therapy machine, and the volumetric-modulated arc therapy (VMAT) plan for the Varian TrueBeam STx. These plans were evaluated and compared using two novel gradient indices in addition to traditional dosimetry metrics for targets and organs at risk (OARs). The steepest border gradient quantified the percent prescription dose fall-off per millimeter at the boundary between the target and adjacent critical structures. This gradient index highlighted the system's ability to spare nearby critical OARs. The volume gradient assessed the extent of dose spread outside the target toward the patient's body.

Results: All plans achieved comparable target coverage and conformity, while IMPT and VMAT demonstrated significantly better uniformity. The GK plans exhibited the highest border gradient, up to 20.9%/mm, followed by small-spot-size IMPT plans and CK plans. Additionally, IMPT plans showed the benefit of reduced dose spread in low-dose regions and the lowest maximum and mean doses to the brainstem and carotid artery.

Conclusions: The advanced external beam radiotherapy modalities evaluated in this study are well-suited for SBRT in skull base reirradiation, which demands precise targeting of tumors with highly conformal doses and steep dose gradients to protect nearby normal structures.

Keywords

stereotactic body radiation therapy, reirradiation, skull base cancer, external beam radiation therapy, Gamma Knife, CyberKnife, proton therapy, dose gradient, intensity-modulated proton therapy, volumetric modulated radiation therapy

Published Open-Access

yes

Recommended Citation

Wang, He; Alsanea, Fahed M; Rhee, Dong Joo; et al., "Advanced External Beam Stereotactic Radiotherapy for Skull Base Reirradiation" (2025). Faculty, Staff and Student Publications. 5331.
https://digitalcommons.library.tmc.edu/uthgsbs_docs/5331