A meta-analysis of zinc levels in breast cancer

BACKGROUND: Breast cancer is the most commonly occurring neoplasm in females, comprising 16% of all female cancers worldwide. Various studies indicate some discrepancies regarding zinc (Zn) levels in various samples of breast cancer patients. OBJECTIVE: The present study evaluated by meta-analysed the published data for Zn levels analyzed in breast tissue, plasma, serum, and hair samples and its relationship with breast cancer. METHODS: The present meta-analysis included 36 studies, all of which were published in the years between 1984 to 2017 and selected by searching the databases MEDLINE, EMBASE, Cochrane Library, PubMed, Scopus, and the ISI Web of Knowledge. The articles were analyzed, and I² statistics were used to examine heterogeneity. The objective analysis was performed on data from the 36 studies, with total 1699 study subjects and 2009 controls. RESULTS: Significant statistical differences overall were observed, based on a random effects model (SMD (95 % CI), -0.78[-1.40, -0.16], P = 0.014). Data from 19 of these studies indicated significant statistical differences between cancerous patients and controls with regard to serum and plasma Zn concentration (SMD [(95 %CI): -1.61(-2.43, -0.79)]. There was a significant statistical difference between the breast tissue and hair as regards Zn status (SMD (95%CI): 2.32(1.42, 3.21)) and (SMD (95v%CI): -1.80(-3.41, -0.20), respectively. Zn concentration levels typically decreased in blood and hair samples of patients with breast cancer, whereas it was elevated in tumor tissues. CONCLUSIONS: There is a significant relationship between lowered serum Zn concentrations and risk of breast cancer onset or recurrences in women, but because of high heterogeneity, we recommend other primary studies.