Abstract
Introduction
The aim of this study was to analyze the impact of inhomogeneous versus homogeneous
dose distribution on local control (LC) and radionecrosis (RN) in patients treated
with fractionated stereotactic radiotherapy (SRT) for newly-diagnosed brain metastases
(BM).
Patients and methods
From 2014 to 2017, 134 patients (median age 61 years) underwent SRT for BM (n = 114 with ≤2, n = 20 with 3–6 BM) at our institution. Treatment was delivered using volumetric modulated
arc therapy on a linear accelerator. Ninety-one consecutive patients (BM = 136) were
irradiated at a dose of 21–23.1 Gy in 3 fractions delivered homogeneously (99% of
the dose had to cover 99% of the planning target volume (PTV)) (group 1) whereas the
following 43 patients (BM = 72) received an inhomogeneous dose of 10 or 11 Gy prescribed
to the isocenter with the 70% isodose line covering the PTV (group 2). Variables analyzed
included dose distribution, age, gender, histology, diagnosis-specific Graded Prognostic
Assessment score, number of brain metastases, presence of extracranial metastases,
and tumor volumes.
Results
After a median follow-up of 12.4 months (range, 1.4–33.1), the 1-year LC and RN rate
were 78% and 7.5% in group 1 and 93% and 0% in group 2, respectively (p = 0.005). In multivariate analysis, improved LC was significantly correlated with
SRT dose distribution (p = 0.009) and tumor volume (p = 0.03). The number of metastases (p = 0.03) and SRT dose distribution (p = 0.04) were both associated with increased risk of RN.
Conclusion
SRT delivered with inhomogeneous dose distribution resulted in better LC and a lower
risk of RN compared to homogeneous distribution.
Keywords
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Article info
Publication history
Published online: July 15, 2018
Accepted:
June 29,
2018
Received in revised form:
May 24,
2018
Received:
March 8,
2018
Identification
Copyright
© 2018 Elsevier B.V. All rights reserved.
