Association between estrogen receptor concentration in breast cancer tissue and bone mineral density.

Both bone and the breast are major target tissues of estrogen actions. The biological actions of estrogen depend on the interaction between estrogen and estrogen receptors (ER) in the target tissues. Therefore, ER concentration in tissues such as breast cancer might be associated with the amount of bone mass. The present study was aimed to examine whether there is a relationship between ER concentration in breast cancer tissue (ER-BCA) and bone mineral density (BMD). Forty-seven pre-menopausal and 34 post-menopausal women with newly diagnosed breast cancer were studied. The ER-BCA ranged from 0 to 339 fmol/mg cytosol protein (mean +/- SD = 68.6 +/- 97.0). Pearson's correlation analyses showed that ER-BCA negatively correlated to BMD of the spine (r = -0.251, p = 0.024), forearm (r = -0.341, p = 0.002), hip (r = -0.373, p = 0.001) and total body (r = -0.317, p = 0.004) in all 81 women. In 47 pre-menopausal women, the ER-BCA negatively correlated to the hip (r = -0.455, p = 0.001) and total body (r = -0.395, p = 0.006) but not to the spine and forearm BMD. Whereas, in 34 post-menopausal women, the ER-BCA negatively correlated to forearm BMD (r = -0.399, p = 0.019). Stepwise multiple regression analyses showed that the ER-BCA independently correlated to hip BMD in all 81 women (r = -0.373, p < 0.01) and in pre-menopausal women (r = -0.486, p < 0.001) and independently correlated to forearm BMD in post-menopausal women (r = -0.399, p < 0.05). The results of this study suggest that the presence of high estrogen receptor concentration in breast cancer tissue might induce a deleterious effect on bone mass particularly in pre-menopausal women.