Leila Jouybari, Marzieh Saei Ghare Naz, Akram Sanagoo, Faezeh Kiani, Fatemeh Sayehmiri, Kourosh Sayehmiri, Ali Hasanpour Dehkordi

Breast cancer (BC) is responsible for a large proportion of incidence of cancer in the world. Identifying the risk factors contributing to the incidence of BC is crucial to find efficient preventive and management strategies for this disease. Several studies have examined Arsenic (As), Cadmium (Cd), and Nickel (Ni) as risk factors for BC. The present study aimed at studying the link between As, Cd, and Ni concentrations and BC by using a meta-analysis. All case-control studies addressing the relationship between As, Cd, and Ni concentrations with BC were identified through electronic search databases (Scopus, ISI Web of Science, PubMed, EmBase, and Cochrane Library). The relevant data obtained from these papers were analyzed by a random-effects model. The heterogeneity of studies was secured by using I2 index. Funnel plots and Egger's test were used to examine publication bias. In the present study, due to different measurement methods used for measuring As, Cd, and Ni, the concentration of these elements was measured in various subgroups (1: plasma, 2: breast tissue, and 3: scalp hair and nail) of individuals with BC and healthy subjects. The overall integration of data from the 3 groups led to the conclusion that there was a significant difference in Cd and Ni statuses between healthy and BC patients; the standard mean difference was 2.65 (95% CI: 1.57-3.73; P=0.000) and 2.06 (95% CI: 1.20-3.32; P=0.000), respectively. Whereas, there was no significant statistical difference in As status between healthy subjects and BC patients; the standard mean difference between them being 0.52 (95% CI: -0.12-1.16; P=0.114). The present study indicates that there is a direct and positive association between Cd and Ni concentrations and BC risk. It is a warning to health care providers and policy makers to find viable solutions and take requisite measures to reduce BC risk in the society.