INCREASED CONCENTRATIONS OF OCTACHLORODIBENZO-P-DIOXIN IN CASES WITH BREAST-CANCER - RESULTS FROM A CASE-CONTROL STUDY

Organochlorines are persistent and highly lipophilic environmental con taminants which bioaccumulate in the food chain. Some of these chemica ls, 2,2-bis(p-chlorophenyl)-1,1,1-trichloroethane (DDT) and polychlori nated biphenyls (PCBs), have been suggested to be of significance in t he aetiology of breast cancer. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TC DD) is an anti-oestrogen in animal studies and should thus lower the r isk of breast cancer. The other isomers of polychlorinated dibenzo-p-d ioxins (PCDDs) or the chemically related polychlorinated dibenzofurans (PCDFs) have not been tested regarding carcinogenesis of the breast. The purpose of this study was to investigate whether PCDDs or PCDFs in fluence the risk for breast cancer. Consecutive patients who underwent surgery for a breast disease between 1993 and 1995 were recruited for the study. Cases were 22 patients with infiltrative breast cancer and controls were 19 patients operated for a benign breast disease during the same time period. Approximately 10 g of breast tissue free from t umour was taken from the specimen and frozen until analysis. Fat was e xtracted, cleaned and analysed with a high-resolution gas chromatograp h coupled to a high-resolution mass spectrometer. Median concentration s of octachlorinated dibenzo-p-dioxin (OCDD) were 598 (170-14,880) and 396 (103-1,847) pg/g lipid in the cases and in the controls, respecti vely. In a multivariate logistic regression analysis controlling for o ther risk factors for breast cancer increased odds ratio (OR) was obta ined for OCDD: 401-1000 pg/g lipid yielded OR 3.8, 95% confidence inte rval (CI) 0.4-39, > 1000 pg/g lipid gave OR 5.2, CI 0.4-72. When the l ipid OCDD variable was examined as a continuous risk factor there was a 1.09 (9%), CI 0.95-1.25, increase in the adjusted OR for breast canc er per 100 unit (pg/g lipid) increase in OCDD. No differences were fou nd between cases and controls for the other six tested PCDDs. Mean con centration of TCDD was in the cases 3.6 (1.0-7.9) and in the controls 3.3 (1.1-6.3) pg/g lipid. For PCDFs no significant differences were fo und between cases and controls. The results were not changed if oestro gen or progesterone receptor status, S-phase fraction and DNA ploidy w ere considered. Breast tissue concentration of OCDD was increased in c ancer patients, whereas the concentrations of other PCDDs and PCDFs we re equal in cases and controls.