Levels of circulating polychlorinated biphenyls and mammographic breast density

Background: Polychlorinated biphenyls (PCBs) are ubiquitous chemicals found in the environment that accumulate in body fat and exhibit endocrine-disrupting properties. These compounds are therefore suspected of influencing breast cancer risk, but results from studies are inconsistent. To further clarify the role of PCBs in the etiology of breast cancer, the present study aimed to examine the relation of 24 PCB congener levels, which were considered individually and in combinations, with mammographic density, one of the risk factors most strongly associated with breast cancer.

Materials and methods: Plasma PCB levels were measured by gas chromatography coupled to mass spectrometry in 106 post-menopausal women for whom mammographic density was measured using a computer-assisted method.

Results: Spearman correlation coefficients adjusted for potentially confounding factors (rs) show that while levels of total PCBs do not appear to be correlated with the percentage mammographic density (rs=-0.19, p=0.08), an increase in the plasma levels of congeners nos. 153, 183, 196 and combined Wolff group 3 PCBs is negatively correlated with the percentage mammographic density (rs=-0.24, p=0.03; rs=-0.30, p=0.004; rs=-0.22, p=0.04; and rs=-0.22, p=0.04 respectively).

Conclusion: Our results suggest that an increase in the plasma levels of some PCB congeners, in particular cytochrome P450 1A1 inducers, is associated with lower mammographic density in post-menopausal women.