Letter: Radiation-Induced Changes After Stereotactic Radiosurgery for Brain Arteriovenous Malformations

To the Editor: We read with great interest the meta-analysis by Ilyas et al,1 which evaluated the incidence of radiation-induced changes (RICs) and identified the risk factors. The authors suggested a high rate of RICs after the treatment of stereotactic radiosurgery (SRS); moreover, the unruptured Arteriovenous malformations (AVMs) and repeat SRS were associated with a higher rate of radiological RIC, and AVMs in deep location had a higher risk of symptomatic RIC. However, there were some issues that should be discussed. Firstly, some studies, which shared the same series of patients, were included in this meta-analysis. A study by Kano et al (2017)2 collected 755 patients with AVMs who underwent single-stage SRS in University of Pittsburgh medical center, from 1987 to 2012; the age of patients ranged from 3 to 79 yr. However, another study by Kano et al (2012)3 was also conducted in University of Pittsburgh medical center from 1987 to 2006, including 155 AVMs patients (<18 yr) who underwent single-stage SRS. The patients in the Kano et al (2012)3 study were a subset of the patients in the other Kano et al (2017)2 study; however, the authors pooled these duplicate data in the symptomatic RIC group and the permanent RIC group, which may affect the results. Thus, the study by Kano et al (2012)3 should not be included.FIGURE.: The association of deep location and permanent radiation-induced changes in AVMs patients underwent SRS.Secondly, the authors suggested that no factor was associated with permanent RIC (Figure1); however, some previous studies2,4 showed that AVMs with a deep location, including basal ganglia, thalamus, and brainstem, had a higher permanent RIC rate. Thus, we pooled the data of 9 studies, which regarded the relationship of deep location and permanent RIC rate, and found the deep location was associated with a higher permanent RIC rate (odds ratio: 5.35, 95% conflict of interest: 2.98-9.61, P < .001, Figure 1), without heterogeneity (P = .64, I2 = 0%). Thirdly, there were some errors in their Table 1.1 The study by Hanakita et al (2015)5 was conducted in the University of Tokyo Hospital (Japan), not in the USA. Moreover, the study by Parkhutik et al (2013)6 included 83 (81.4%) patients undergoing single-session SRS and 19 (18.6%) patients treated by second SRS, not only by single-session SRS, which may need revision. Disclosure The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.