Abstract
INTRODUCTION: The aim of this meta-analysis was to summarize the evidence on the serum/plasma leptin concentrations in breast cancer (BC) patients, as well as the associations between leptin G-2548A gene polymorphisms and susceptibility to BC. MATERIAL AND METHODS: Potentially relevant studies about serum/plasma leptin levels and leptin G-2548A gene polymorphism were selected using the electronic databases PubMed, EMBASE and The Cochrane Library (from January 1 1995 to Jun 30 2017, no language restrictions). The potential sources of heterogeneity were assessed by the Q statistic and quantified using I(2) ; publication bias was qualitatively assessed by funnel plot and quantitatively assessed by Egger's linear regression test. RESULTS: A total of 1141 articles were retrieved after database searches, and 27 studies with 9516 subjects (4542 BC patients/4974 controls) were finally included. The results indicated that BC patients had significantly higher leptin levels compared with healthy controls (SMD = 1.65, 95% CI: 1.21-2.09, p < 0.001), but there was no association between leptin G-2548A polymorphism and BC (OR = 1.05, 95% CI: 0.80-1.39, p = 0.722). Subgroup analyses demonstrated increased leptin levels in BC patients of different region, race, body mass index and waist circumference. CONCLUSIONS: Our results revealed a significantly higher leptin level in BC patients than in healthy controls, but no association between leptin G-2548A polymorphism and BC susceptibility was found.