LAUSR

Literature searching concerns. Dr Zu-Bing Mei et al (2018) identify two studies that they claim are not included in our analysis despite meeting the inclusion criteria. Furthermore, they indicate that had these articles been included, the results of our meta-analysis may have been different. In order to clarify, we would like to point out that one of the cited articles (Saigusa et al, 2010) was identified by our search strategy; however, the authors did not include sufficient data for inclusion in our meta-analysis. The authors were contacted by email but did not respond to our request for further data. The second study identified by Mei et al (Yu et al, 2016) was not identified by our search strategy. This is likely because it was published in the same month as we ran our search strategy and therefore may not have been indexed at that time. On review of (Yu et al, 2016), the article reports on 54 osteosarcoma patients, demonstrating a significant association between elevated CXCL12 expression and overall survival (HR 2.64 (1.12–6.20)). This is a small study and the resultant effect estimate is associated with a reasonably wide confidence interval; it is unlikely to have significantly altered our overall survival estimates.