A Global Regional Comparison of the Risk of Breast Cancer in Woman Using Oral Contraceptives-Systematic Review and Meta-Analysis.

: Incidence of breast cancer (BrCa) may be correlated with country development, with a rise in cases anticipated in regions of the world that are currently undergoing an economic transformation. Herein, differences with regard to the occurrence of breast cancer between individual countries may depend on the distribution of risk factors, the level of early detection, also ethnicity and race, as well as clinical characteristics. The aim of our study was to identify and then investigate observational studies in which the risk of breast cancer was associated with the use of oral hormonal contraceptives (OCs), with particular emphasis on geographic region, and to conduct a systematic review and meta-analysis of the obtained data. : RR (relative risk) was calculated and displayed in forest plots for visual interpretation. Accordingly, 74 studies involving a total of 198,579 women were eligible for inclusion in the meta-analysis. This is the first meta-analysis to comprehensively summarize the evidence between OC use and BrCa risk in connection with geographical region. : The cumulative results of the meta-analysis for specific parts of the world are: Africa (RR = 1.16, = 0.216) and the Americas (RR = 1.03, = 0.597); Asia (RR = 1.29, = 0.014); European countries (RR = 1.01, = 0.904); and Middle East countries (RR = 1.29, = 0.043). Subgroup analyses showed an increased risk of BrCa for the analyzed variables that depended upon the geographical region. : Our meta-analysis suggests that OC use may be associated with a higher BrCa risk, although a statistically significant association was not found for all geographical regions of the world.