Evaluation of the association between vitamin D and lung cancer skin metastasis: A protocol for systematic review

Background: This study aims to investigate the association between vitamin D (VD) and lung cancer skin metastasis (LCSM). Methods: The following databases will be retrieved from the beginning to the present of each database without language limitation: PUBMED, EMBASE, Cochrane Library, Web of Science, CBM, and CNKI. The reference lists of included trials and other sources will also be checked. Two researchers will independently undertake literature selection, data collection, and study quality evaluation. We will utilize a fixed or random-effect model to pool the data according to the heterogeneity test. The RevMan 5.3 software will be used to analyze the data and perform meta-analysis. Results: This study will summarize high quality study to explore the association between VD and LCSM. Conclusion: The findings of this study will help to judge whether there is association between VD and LCSM. Ethics and dissemination: No research ethical approval is required in this study, because it will only analyze published data. It is expected to disseminate through a peer-reviewed journal. Study registration: osf.io/ph2au.