DDE BURDEN AND BREAST CANCER RISK

Abstract

The exposure to DDT in relation to breast cancer (BC) risk received increasing attention since the beginning of the 90's. Contradicting results are published regarding the supposed relationship between body burden levels of p,p'-DDE -the main DDT metabolite- and BC. In this paper we argue that such conflict might be explained by methodological differences crosswise those studies. To such aim a meta-analysis of 22 articles was performed using the DerSimonian and Laird method for random effects models. The Q-statistic was used to identify heterogencity in the outcome variable across different studies. The gradient of p,p'-DDE exposure in epidemiological studies was homogenized to ng/g. The potential for publication bias was examined with the Begg's test and methodological features of studies are then discussed. The summary odds ratio for selected studies was 0.97 (95% CI, 0.87–1.09) in which the gradient of exposure ranged from 84.37 to 12,948 ng/g. No overall heterogeneity in the OR (c2 = 27.93; df = 23; p = 0.218) was observed. Neither the design of the study, nor the lack for breastfeeding control or the type of biological specimen where p,p'-DDE levels were measured, were causes of heterogeneity throughout the studies. Evidence of publication bias was not found (p = 0.253). These results do not lend support to the idea that a relationship between p,p'-DDE and BC risk could exist. Nevertheless, the exposure to DDT during critical periods of human development, from conception to adolescence, and individual variations in the metabolizing enzymes of DDT or its derivatives are still questions to be researched in regards to adult BC.