Multifraction Stereotactic Radiosurgery to Large Brain Metastases: Is This Scheme Effective and Safe?

Abstract

Many fractionation regimens have been described for the treatment of large brain metastases with stereotactic radiosurgery (SRS). The purpose of this analysis is to demonstrate the efficacy and the tolerance of multifraction stereotactic radiosurgery (mSRS), 3 fractions, in patients with large brain metastases. Were reviewed all patients with brain metastases treated with mSRS (3 fractions) at a single institution. Patients with large brain metastases were the majority population, but patients who were not appropriate candidates for single fraction SRS were treated with mSRS and included as well. Prognostic factors including Ds-GPA, Score Index for Radiosurgery (SIR), number of lesions, systemic disease status, primary site, PTV volume, dose (3 schemes were used due a constraint of the organ at risk - 7 Gy, 8 Gy or 9 Gy/fraction), use of whole brain radiotherapy (WBRT) either pre or post SRS, surgery and the use of systemic therapy were all evaluated. The toxicity was graded using the CTCAE V. 4.0. Kaplan- Mayer and Log-Rank test were used for survival curve calculations. Chi-square test was used for comparative analysis with a significance level of 0.05. Between March 2015 and November 2018, 86 patients were enrolled, of which 2 were excluded due to loss to follow-up and 144 lesions treated. The median follow-up was 9.0 months. The patient characteristics are shown in Table 1. The overall survival (OS) at 12 and 24 months was 43% and 21.6%, respectively, with a median overall survival of 10 months. Death due to neurological failure was 14.5%. Local control at 12 months was 81.3%, with 47.6% developing new lesions after the first mSRS. There wasn’t a correlation between local control and dose/fraction, PTV volume and the other factors. There were 4 patients with acute grade 3 toxicity (paresthesia), reversible with corticosteroids. The most common symptom was headache, grade 1 and 2, (23.5%). Eight patients had grade 1-2 seizures. The radionecrosis rate was 9.5%, and four patients had symptomatic radionecrosis. The PTV volume average was 20.87 cc (1-140 cc). In multivariate analysis, Ds-GPA, SIR, KPS, primary site (melanoma and breast were better) and systemic progression status had a statistically significant effect on OS. The dose/fraction and PTV volume did not correlate with toxicity or radionecrosis. This mSRS scheme of 3 fractions to large brain metastases showed good local control with low complication rates, in the studied population. In our retrospective analysis of 84 patients, we conclude that this 3 fraction mSRS is safe and effective. A prospective trial is warranted to compare and evaluate the best SRS regimens for this approach.Abstract 2160; Table 1Patients CharacteristicsAge (median)54.5 y (22-81)Numb. Lesions: 1 - 3; >3;91.6%/ 8.4%Ds-GPA 0-1; 1.5 - 2.5; >2.5;23.8%/ 29.8%/ 46.4%/Primary Lung; Breast; Melanoma; Others;39.3%/ 28.6%/ 8.3%/ 23.8%Fractionation 7 Gy x 3; 8 Gy x 3; 9 Gy x 3;8.3%/ 29.8%/ 61.9%/WBRT Pre mSRS; Pos mSRS; No;13.1%/ 23.8%/ 63.1%/ Open table in a new tab