Authors
Elisabete Weiderpass et al

Title
Organochlorines and Endometrial Cancer

Journal
Cancer Epidemiology Biomarkers & Prevention Vol. 9,487-493, 2000

Summary
There is widespread concern that environmental pollutants such as dichlorodiphenyltrichloroethane (DDT) and polychlorinated biphenyls (PCBs) may cause or contribute to the development of cancer in humans. It is thought that, although weakly estrogenic, organochlorines may increase overall estrogen exposure and thus increase the risk of developing breast cancer. The authors of the present paper propose that because the endometrium is more sensitive to estrogenic stimulation than the breast, the adverse effects of estrogenic organochlorines should be more easily detected in the endometrium. Therefore the goal of this study was to test the hypothesis that elevated blood concentrations of specific organochlorines is associated with an increased risk of endometrial cancer. To test this hypothesis the authors carried out a population-based case-control study of organochlorine pesticides and PCB congeners in 154 endometrial cancer cases and 205 population controls in Sweden. Women 50-74 years of age, resident between February 1996 and November 1997 in 12 Swedish counties on the largest Swedish lakes were recruited into the study. It was assumed that the intake of organochlorine compounds through ingestion of contaminated fish would be higher in these counties than elsewhere in Sweden. Since hormone replacement therapy or prior hysterectomy are recognized risk factors for endometrial cancer, women reporting these were excluded from this study. Subsequently, 134 women with endometrial cancer were excluded because they had used hormone replacement therapy, leaving 154 cases in the study. The lipid portion of serum samples was analyzed for 10 organchlorine pesticides and 10 PCB congeners. Samples from cases were collected immediately after diagnosis and before surgery or any other cancer therapy. There was no difference between cases and controls regarding fish consumption patterns, but women in the control group reported more breast-feeding than cases (a major excretory route for organochlorine compounds).

Among DDT metabolites, the concentration of p, p'-DDE (the principal metabolite of p, p'-DDT) was highest (600-700ng/g lipid) and the average concentrations of other pesticides were usually lower by a factor of 10 or more. For all compounds, the range of exposure was substantial both among cases and controls. In unadjusted analyses, median concentrations of p,p'-DDT, p,p'-DDE, ß-HCH, and oxychlordane were higher among cases than controls. However, after adjustment for age and BMI in logistic regression, ORs were close to unity and there was no evidence of exposure-risk relationships across quartiles of contaminant concentrations. In the analyses of organochlorines as continuous variables, no associations were found between risk for endometrial cancer and any of the 10 pesticides evaluated. Among the 10 PCB congeners, CB153 had the highest concentration (mean ~ 236ng/g lipid), whereas CB28, CB52, and CB102 often had concentrations below the limit of quantification (2ng/g lipid). Unadjusted mean concentrations of CB28 and CB118 were higher among cases than controls. However, after adjustment there was no significant trend in risk. Finally, in the analysis of the 10 different PCB measurements in continuous form, there was no significant association between any of the congeners and endometrial cancer risk. On the other hand, after standardizing for lipid content in different tissues, the mean concentration of organochlorines in this study were in the lower range compared to those reported previously for controls in North American and European breast cancer studies, where sampling occurred in the late 1980s and early 1990s and average concentrations were 1,020-2,200 ng/g lipid for p,p'-DDE and 350-1,300 ng/g lipid for total PCBs. The somewhat lower average exposure in this study (sampling 1996-1997) at least partially reflects the continuous decline in Europe and North America after banning of these compounds. The data do not support the hypothesis that, in this population, organochlorine exposure increases the risk for endometrial cancer.