Dosimetric Factors Related to Radiation Necrosis After 5-Fraction Radiosurgery for Patients With Resected Brain Metastases

• Type of Material: Article
• Authors: Daniel G. Tanenbaum, Emory University; Zachary Buchwald, Emory University; Jaymin Jhaveri, Emory University; Eduard Schreibmann, Emory University; Jeffrey Switchenko, Emory University; Roshan S. Prabhu, Carolinas HealthCare System; Mudit Chowdhary, Rush University; Mustafa Abugideiri, Emory University; Neil T. Pfister, Emory University; Bree Eaton, Emory University; Shannon Kahn, Emory University; Jeffrey Olson, Emory University; Hui-Kuo Shu, Emory University; Ian Crocker, Emory University; Walter J Curran, Emory University; Kirtesh R. Patel, Yale University
• Language: English
• Date: 2020-01-01
• Publisher: Elsevier Science Inc.
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2019 American Society for Radiation Oncology
• License: Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1016/j.prro.2019.09.014
• Title of Journal or Parent Work: Practical Radiology Oncology
• Volume: 10
• Issue: 1
• Start Page: 36
• End Page: 43
• Grant/Funding Information: Research reported in this publication was supported in part by the Biostatistics and Bioinformatics Shared Resource of Winship Cancer Institute of Emory University and National Institutes of Health and the National Cancer Institute under award number P30CA138292.
• Keywords: Science & Technology; PREDICTOR; PARADIGM; HYPOFRACTIONATED STEREOTACTIC RADIOTHERAPY; THERAPY; Oncology; Life Sciences & Biomedicine; SURGICAL RESECTION; RADIONECROSIS; SINGLE METASTASES; TUMORS; Radiology, Nuclear Medicine & Medical Imaging; CAVITY; VOLUME
• Research Categories: Health Sciences, Oncology

Abstract

Purpose: Stereotactic radiosurgery (SRS) is increasingly used in the management of patients with resected brain metastases (rBMs). A significant complication of this therapy can be radiation necrosis (RN). Despite radiation therapy dose de-escalation and the delivery of several rather than a single dose fraction, rates of RN after SRS for rBMs remain high. We evaluated the dosimetric parameters associated with radiographic RN for rBMs. Methods and Materials: From 2008 to 2016, 55 rBMs at a single institution that were treated postoperatively with 5-fraction linear accelerator–based SRS (25-35 Gy) with minimum 3 months follow-up were evaluated. For each lesion, variables recorded included radiation therapy dose to normal brain, location and magnitude of hotspots, clinical target volume (CTV), and margin size. Hotspot location was stratified as within the tumor bed alone (CTV) or within the planning target volume (PTV) expansion margin volume (PTV minus CTV). Cumulative incidence with competing risks was used to estimate rates of RN and local recurrence. Optimal cut-points predicting for RN for hotspot magnitude based on location were identified via maximization of the log-rank test statistic. Results: Median age for all patients was 58.5 years. For all targets, the median CTV was 17.53 cm3, the median expansion margin to PTV was 2 mm, and the median max hotspot was 111%. At 1 year, cumulative incidence of radiographic RN was 18.2%. Univariate analysis showed that max hotspots with a hazard ratio of 3.28 (P = .045), hotspots within the PTV expansion margin with relative magnitudes of 105%, 110%, and 111%, and an absolute dose of 33.5 Gy predicted for RN (P = .029, P = .04, P = .038, and P = .0488, respectively), but hotspots within the CTV did not. Conclusions: To our knowledge, this is the first study that investigated dosimetric factors that predict for RN after 5-fraction hypofractionated SRS for rBM. Hotspot location and magnitude appear important for predicting RN risk, thus these parameters should be carefully considered during treatment planning.