HIGH NATURAL ESTROGEN LEVELS LINKED TO INCREASED RISK OF BREAST CANCER

Breast cancer is two to four times more likely to develop in women who have high levels of natural estrogen, New York University School of Medicine researchers report.

In a study published Wednesday in the Journal of the National Cancer Institute, the scientists say that a comparison of estrogen levels in stored blood samples of 130 women with breast cancer with frozen specimens from 251 cancer-free women of the same age showed a strong correlation between the natural hormone and the disease."In the highest exposure group, we observe between a two- and fourfold increase in breast cancer," said Dr. Paolo G. Toniolo of NYU. "The implication is that whatever in the environment may push the level of hormones in a woman's body to a higher level may cause her risk of breast cancer to increase."

The study is the largest yet to address the relationship between natural estrogen and breast cancer, said Toniolo. It is based on blood samples that were drawn years before any breast cancer was diagnosed. The specimens were frozen for up to 51/2 years and then thawed to perform the analysis, he said.

Toniolo said the study results cannot be related to any cancer risk that might be linked to estrogen therapy, the practice of giving postmenopausal women hormone drugs to combat bone thinning or heart disease.

Women in the study had a mean age of 58.9 years and all had been in menopause for at least six months, based on the absence of a menstrual cycle.

Levels of estrogen of all of the women were within what is considered a normal range, said Toniolo, but the levels were up to 32 percent higher among those with breast cancer.

Robert Smith, Ph.D., an epidemiologist with the American Cancer Society, said the research is important because it is the first large study that specifically confirms the link between natural estrogen and breast cancer.

Though there have been studies implying a connection, said Smith, "there really has been a paucity of direct evidence linking endogenous estrogens to breast cancer."