The strength of a woman’s bones may be the most powerful predictor yet of her risk of breast cancer.
For the second time in recent months, a study found that older women with very strong, healthy bones run a sharply higher risk of breast cancer, a disease that kills 44,000 people in the United States annually.
Having strong bones is ordinarily thought to be a good thing, and the bones themselves are almost certainly not the problem. Rather, doctors believe healthy bones reflect a high lifetime exposure to estrogen, the female sex hormone also implicated in breast cancer.
“The suspected link is estrogen - not the kind that doctors give you when you enter menopause but the kind that is naturally occurring in the body during a woman’s premenopausal years,” Dr. Douglas Kiel said.
Kiel, a geriatrics specialist at the Hebrew Rehabilitation Center for the Aged in Boston, is co-author of a study in today’s issue of the New England Journal of Medicine. It found that older women with the strongest bones have almost four times the breast cancer risk of women with weak bones.
This could make bone strength the single most powerful predictor of breast cancer risk - even more telling than a family history of the disease, which increases risk two to three times.
Weak bones - a condition called osteoporosis - are extremely common among elderly women. Many are already routinely given a test for bone strength.
Kiel said he does not yet urge wholesale bone testing to estimate cancer risk. But he said that when the test is already done for other reasons, it can be combined with other known risk factors to help single out women who are at especially high risk.
Knowing their risk is especially great should encourage women to get yearly mammograms, which are recommended for all those over 50.
The findings were drawn from the Framingham Heart Study, which has followed the health of residents of a Boston suburb since 1948.
Kiel cautioned that the findings in no way mean that women shouldn’t try to keep their bones healthy. While estrogen production powerfully influences bone strength, exercise and calcium in the diet can also help keep bones strong and do not increase cancer risk.
Doctors routinely give estrogen to ease the hot flashes and other symptoms of menopause. Some stay on the supplements throughout old age as a way of preventing bone loss and heart disease, a far bigger killer than breast cancer.