Breast adipose tissue concentrations of polychlorinated biphenyls and other organochlorines and breast cancer risk

Numerous studies have examined the relationship between organochlorines and breast cancer, but the results are not consistent. In most studies, organo chlorines were measured in serum, but levels in breast adipose tissue are h igher and represent cumulative internal exposure at the target site for bre ast cancer. Therefore, a hospital-based case-control study was conducted in Ontario, Canada to evaluate the association between breast cancer risk and breast adipose tissue concentrations of several organochlorines. Women sch eduled for excision biopsy of the breast were enrolled and completed a ques tionnaire. The biopsy tissue of 217 cases and 213 benign controls frequency matched by study site and age in 5-year groups was analyzed for 14 polychl orinated biphenyl (PCB) congeners, total PCBs, and 10 other organochlorines , including p,p'-1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene. Multiple log istic regression was used to assess the magnitude of risk. While adjusting for age, menopausal status, and other factors, odds ratios (ORs) were above 1.0 for almost all organochlorines except five pesticide residues. The ORs were above two in the highest concentration categories of PCB congeners 10 5 and 118, and the ORs for these PCBs increased linearly across categories (Ps for trend less than or equal to 0.01). Differences by menopausal status are noted especially for PCBs 105 and 118, with risks higher among premeno pausal women, and for PCBs 170 and 180, with risks higher among postmenopau sal women, Clear associations with breast cancer risk were demonstrated in this study for some PCBs measured in breast adipose tissue.