Letter regarding Wen X.Y. et al. entitled “Matrix metalloproteinase 2 expression and survival of patients with osteosarcoma: a meta-analysis”
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In a recent issue of Tumor Biology, Xiaoyang Wen and his workmates published an article  entitled “Matrix metalloproteinase 2 expression and survival of patients with osteosarcoma: a meta-analysis”. In this study, the investigators performed a meta-analysis to derive a precise estimate of the prognostic role of MMP2 expression in patients with osteosarcoma. The investigators concluded that osteosarcoma patients with high MMP2 expression have poorer prognosis compared with those with low MMP2 expression. However, we have several opinions that we would like to raise to the investigators.
Firstly, the investigators just searched three electronic databases (PubMed, EMBASE, and Wanfang databases). The small number of required papers would be an important limitation of the review. We hope that more electronic databases can be systematically searched. In the same time, the investigators had not focused specifically on the issue of the completeness of the search strategy report for databases. They just described the retrieval strategy by using the keywords such as, “osteosarcoma” or “osteosarcomas”, and “MMP2” or “matrix metalloproteinase-2”. We suggest that the investigators should provide us the details of the retrieval strategy and the flowchart of selection.
Secondly, in the results section, the investigators just provide us a forest plot to clarify the prognostic role of MMP2 expression in patients with osteosarcoma. Inexplicably, what dose the forest plot and the RR value mean. In our opinion, the investigators should clarify its prognostic role with forest plots of 5-year overall survival (OS) rate and 5-year disease free survival (DFS) rate.
Thirdly, the investigators included five cohort studies [2, 3, 4, 5, 6] including 297 patients with osteosarcoma. However, the investigators did not provide us any characteristics of these eligible studies. We suggest that the investigators should provide us its characteristics in tables to make us read the meta-analysis well.
Finally, the investigators did not follow the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). As a minor suggestion, adding PRISMA checklist some summery could make this manuscript better.
Moreover, more studies with larger sample size are needed to get a more precise estimate of the prognostic role of MMP2 expression in osteosarcoma.
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