RESUMO
PURPOSE: PIWIL2, one of the PIWI gene subfamily, is now thought to be closely related to poor clinical outcomes in various cancers. The aim of this research was to comprehensively estimate its predictive value in the prognosis of cancer patients. METHODS: We thoroughly searched PubMed, Web of Science and Embase databases for eligible articles published until April 4th 2019, in which the association between cancer prognosis and PIWIL2 expression level was studied. Study qualities were assessed using NOS criteria. We performed analyses by Stata SE 12.0 and RevMan 5.3. The primary endpoints contained overall survival (OS), cancer-specific survival (CSS), metastasis-free survival (MFS), recurrence-free survival (RFS) and disease-free survival (DFS). RESULTS: Ten studies containing 2116 patients with 8 various solid cancers were finally included. The outcomes indicated that cancer patients with higher PIWIL2 expression level had significant shorter OS (HR:2.20, 95%CI:1.25-3.88, p=0.006), DFS/RFS/MFS (HR:2.96, 95%CI:1.68-5.23, p<0.001), CSS (HR: 2.12, 95%CI: 1.40-3.23, p<0.001) than cancer patients with lower PIWIL2 expression level. What's more, PIWIL2 over-expression was significantly correlated to more lymph node metastasis (LNM) (OR:1.61, 95%CI:1.28-2.02, p<0.001). And PIWIL2 expression was not significantly correlated with age, gender, differentiation, tumor invasion, tumor size, TNM stage and distant metastasis (DM). CONCLUSIONS: A higher expression level of PIWIL2 may predict a poorer prognosis of cancer patients. And its prognostic values are not significantly influenced by clinicopathological characters. Therefore, PIWIL2 could serve as a personalized prognostic predictor in cancers in the future.