Bone mass levels may be another indicator to determine a woman's risk of developing breast cancer, researchers have discovered.

Postmenopausal women with the highest bone mass face a 3.5 times greater chance of developing breast cancer, compared with those with the lowest levels.

It seems likely that women with the highest bone mass after menopause have had HRT (hormone replacement therapy) and have been exposed to high levels of estrogen. While doctors have known that high levels of estrogen are a risk factor for breast cancer, it has been hard to determine the risk because of fluctuations in estrogen levels during the menstrual cycle.

To test the theory, researchers from Boston University studied 1,373 women aged between 47 and 80 who had no history of breast cancer. Of the 91 patients who went on to develop breast cancer, most were in the higher quartiles of bone mass levels (NEJM 1997; 336: 611-7).

Estrogen treatment given early in the menopause and carried into late life is likely to achieve the highest levels of bone density, researchers have found. But benefits were almost as great when treatment is started when the woman is 60 (JAMA, 1997; 277: 543-7).

For more information, see the WDDTY Guide to the Menopause, and vol 4, nos 9 and 10.