Effect of Target Changes on Target Coverage and Dose to the Normal Brain in Fractionated Stereotactic Radiation Therapy for Metastatic Brain Tumors

Hideharu Miura, PhD; Masahiro Kenjo, MD, PhD; Yoshiko Doi, MD, PhD; Taro Ueda, MD; Minoru Nakao, PhD; Shuichi Ozawa, PhD; Yasushi Nagata, MD, PhD

Advances in Radiation Oncology (Nov 2023)

Effect of Target Changes on Target Coverage and Dose to the Normal Brain in Fractionated Stereotactic Radiation Therapy for Metastatic Brain Tumors

Hideharu Miura, PhD,
Masahiro Kenjo, MD, PhD,
Yoshiko Doi, MD, PhD,
Taro Ueda, MD,
Minoru Nakao, PhD,
Shuichi Ozawa, PhD,
Yasushi Nagata, MD, PhD

Affiliations

Hideharu Miura, PhD: Hiroshima High-Precision Radiation therapy Cancer Center, 3-2-2, Futabanosato, Higashi-ku Hiroshima, 732-0057, Japan; Department of Radiation Oncology, Institute of Biomedical & Health Sciences, Hiroshima University, 1-2-3 Kasumi Minami-ku Hiroshima-shi, Hiroshima 734-8553, Japan; Corresponding author
Masahiro Kenjo, MD, PhD: Hiroshima High-Precision Radiation therapy Cancer Center, 3-2-2, Futabanosato, Higashi-ku Hiroshima, 732-0057, Japan; Department of Radiation Oncology, Institute of Biomedical & Health Sciences, Hiroshima University, 1-2-3 Kasumi Minami-ku Hiroshima-shi, Hiroshima 734-8553, Japan
Yoshiko Doi, MD, PhD: Hiroshima High-Precision Radiation therapy Cancer Center, 3-2-2, Futabanosato, Higashi-ku Hiroshima, 732-0057, Japan; Department of Radiation Oncology, Institute of Biomedical & Health Sciences, Hiroshima University, 1-2-3 Kasumi Minami-ku Hiroshima-shi, Hiroshima 734-8553, Japan
Taro Ueda, MD: Hiroshima High-Precision Radiation therapy Cancer Center, 3-2-2, Futabanosato, Higashi-ku Hiroshima, 732-0057, Japan
Minoru Nakao, PhD: Hiroshima High-Precision Radiation therapy Cancer Center, 3-2-2, Futabanosato, Higashi-ku Hiroshima, 732-0057, Japan; Department of Radiation Oncology, Institute of Biomedical & Health Sciences, Hiroshima University, 1-2-3 Kasumi Minami-ku Hiroshima-shi, Hiroshima 734-8553, Japan
Shuichi Ozawa, PhD: Hiroshima High-Precision Radiation therapy Cancer Center, 3-2-2, Futabanosato, Higashi-ku Hiroshima, 732-0057, Japan; Department of Radiation Oncology, Institute of Biomedical & Health Sciences, Hiroshima University, 1-2-3 Kasumi Minami-ku Hiroshima-shi, Hiroshima 734-8553, Japan
Yasushi Nagata, MD, PhD: Hiroshima High-Precision Radiation therapy Cancer Center, 3-2-2, Futabanosato, Higashi-ku Hiroshima, 732-0057, Japan; Department of Radiation Oncology, Institute of Biomedical & Health Sciences, Hiroshima University, 1-2-3 Kasumi Minami-ku Hiroshima-shi, Hiroshima 734-8553, Japan

Journal volume & issue: Vol. 8, no. 6
p. 101264

Abstract

Read online

Purpose: We evaluated the dosimetric effect of tumor changes in patients with fractionated brain stereotactic radiation therapy (SRT) on the tumor and normal brain using repeat verification magnetic resonance imaging (MRI) in the middle of the treatment period. Methods and Materials: Fifteen large intracranial metastatic lesions with fractionated SRT were scanned employing standardized planning MRI (MRI-1). Repeat verification MRI (MRI-2) were performed during the middle of the irradiation period. Gross tumor volume (GTV) was defined as the volume of the contrast-enhancing lesion on T1-weighted MRI with gadolinium contrast agent. The doses to the tumor and normal brain were evaluated on the MRI-1 scan. Beam configuration and intensity on the initial volumetric modulated arc therapy plan were used to evaluate the dose to the tumor and the normal brain on MRI-2. We evaluated the effect of D98% (percent dose irradiating 98% of the volume) on the GTV using the plans on the MRI-1 and MRI-2 scans. For the normal brain, the V90%, V80%, and V50% (volume of the normal brain receiving >90%, 80%, and 50% of the prescribed dose, respectively) were investigated. Results: Three (20% of the total) and 4 (26% of the total) tumors exhibited volume shrinkage or enlargement changes of >10%. Five (33% of the total) tumors exhibited volume shrinkage and enlargement changes of <10%. Three tumors (20% of the total) showed no volume changes. D98% of the GTV increased in patients with tumor shrinkage because of dose inhomogeneity and decreased in patients with tumor enlargement, with a coefficient of determination of 0.28. The V90%, V80%, and V50% increase with decreasing tumor volumes and were linearly related to the tumor volume difference with a coefficient of determination values of 0.97, 0.98, and 0.97, respectively. Conclusions: Repeat verification MRI for brain fractionated SRT during the treatment period should be considered to reduce the magnitude of target underdosing or normal brain overdosing.

Published in Advances in Radiation Oncology

ISSN: 2452-1094 (Online)
Publisher: Elsevier
Country of publisher: United States
LCC subjects: Medicine: Medicine (General): Medical physics. Medical radiology. Nuclear medicine; Medicine: Internal medicine: Neoplasms. Tumors. Oncology. Including cancer and carcinogens
Website: http://www.journals.elsevier.com/advances-in-radiation-oncology/

About the journal