Main Session
Sep
27
PQA 01 - Gastrointestinal Cancer and Central Nervous System
2155 - Single Radiosurgery Prescription Increases Efficiency without Clinical Detriment in Patients with Multiple Brain Metastases of Varying Sizes: A Retrospective Review of Zero Margin, Frameless, Single-Isocenter, Multitarget Radiosurgery
Presenter(s)
Luke Moradi, MD - University of Alabama at Birmingham, Birmingham, AL
L. Moradi1, R. A. Popple1, R. Travis1, S. Marcrom2, J. Hoyle1, C. D. Willey1, H. Boggs1, J. A. Pogue1, J. M. Markert3, R. Sullivan1, K. Riley3, and J. B. Fiveash1; 1University of Alabama at Birmingham Department of Radiation Oncology, Birmingham, AL, 2University of Alabama at Birmingham, Department of Radiation Oncology,, Birmingham, AL, 3University of Alabama at Birmingham Department of Neurosurgery, Birmingham, AL
Purpose/Objective(s):
Single-fraction stereotactic radiosurgery (SRS) is typically used for tumors <2 cm, whereas fractionated SRS (fSRS) is preferred for larger tumors to reduce the risk of radionecrosis. In patients with mixed tumor sizes, generating separate treatment plans increases planning complexity, treatment time, and physics quality assurance (QA) requirements. Some centers instead use a single treatment plan, with fractionation determined by the largest lesion. This study evaluated whether local control of small brain metastases (<2 cm) is compromised when treated with fSRS rather than SRS.Materials/Methods:
This retrospective review included 496 patients with 2,460 brain metastases treated with SRS or fSRS. All tumors within a given plan were treated with the same number of fractions (1, 3, or 5), typically dictated by the largest lesion. Only tumors <2 cm were included, thereby excluding the larger lesions that prompted the use of fSRS. Treatments were delivered using single-isocenter, frameless, volumetric modulated arc therapy.Results:
One-year local control did not differ significantly between SRS and fSRS (96% vs. 97%; p = 0.326). Among the most common dose regimens, one-year local control was 94% with 18 Gy and 97% with 20 Gy SRS, compared with 99% for 9 Gy × 3 and 96% for 6 Gy × 5 fSRS. Overall freedom from grade =3 toxicity was 99%, with no significant difference between regimens (p = 0.258). On multivariable analysis, melanoma histology (HR 2.96; p = 0.004), breast cancer histology (HR 2.56; p = 0.007), and tumor volume (HR 1.68; p < 0.001) were associated with worse local control. Dose regimen was not a significant predictor of local control.Conclusion:
Using a single prescription/plan reduces planning complexity, treatment time, and physics QA burden. In this study, no differences in local control or toxicity were observed when small brain metastases were treated with SRS versus fSRS.