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Nipple fluid flags breast cancer risk.

One in nine American women will develop breast cancer at some time during her life. The most common malignancy affecting women, breast cancer killed almost 45,000 women in the United States last year alone. Unfortunately, physicians have no routine procedure for determining which symptomless women are at increased risk of this disease. But a team of San Francisco-area researchers has just reported results of a promising prognostic approach: painless extraction of sloughed-off breast cells.

"Someday this kind of approach is going to be enormously important," says Mary-Claire King, an epidemiologist at the University of California, Berkeley.

Beginning in 1973, epidemiologist Nicholas L. Petrakis of the University of California, San Francisco, and his co-workers began recruiting volunteers for a breast cancer screening survey. Over the next seven years, they attempted to siphon off small amounts of breast fluid from 2,701 white women, using a nipple aspirator similar to the breast pumps used by many nursing mothers.

In the breasts of adult women, even those who have never given birth, "there is some [fluid] secretion and reabsorption going on all the time," Petrakis notes. These secretions, which resemble the colostrum produced by new mothers, also harbor some cells from the tissue in which breast cancers form. Petrakis' team extracted a drop or two of these secretions from the nipples of most volunteers, none of whom was pregnant, lactating or suffering from breast cancer.

Between June 1988 and April 1991, the researchers tracked down and then surveyed 87 percent of the former volunteers, 104 of whom had developed breast cancer. Nearly all women age 55 or older during testing fit into the same cancer-incidence group, regardless of whether the researchers had been able to obtain breast secretions; only those whose secretions contained highly abnormal breast cells at the time of testing faced a higher risk of cancer.

However, a significant elevation in breast cancer appeared among volunteers under 55 who possessed extractable fluid, especially those whose secretions contained abnormal cells. Compared with younger volunteers whose breasts emitted no fluid, women whose sampled secretions contained even healthy cells faced a 6.4-fold increase in cancer risk. Younger women whose secretions showed hyperplasia (mild or moderately proliferating normal cells) faced 9.5 times the cancer risk of women not expressing fluid, and those whose cells appeared more precancerous (described as atypical hyperplasia) faced 16.3 times the risk.

These findings appear in the Jan. 15 American Journal of Epidemiology, released last week.

Why should breasts with no extractable fluid be less prone to cancer? Higher levels of secretions may increase the exposure of breast tissue to cancer-fostering chemicals in the body, the researchers suggest. Biochemical tests they performed on extracted fluids showed that the secretions contain hormones, cholesterol and cholesterol-oxidation products. What's more, Petrakis says, secretion from "8 percent or so of the women came up positive in the Ames test," a bacterial assay to identify possible carcinogens.

But "having been a subject giving breast fluid from time to time, I know that sometimes you can get fluid and sometimes you can't," says King; so an inability to express fluid may not be "a lifelong feature." She also believes the current technique's sensitivity "is way too low" for clinical reliability: By not drawing from all breast-secretion ducts, it may miss many precancerous lesions.

The technique nonetheless offers "a very useful research tool," says David Thomas of the Fred Hutchinson Cancer Research Center in Seattle.
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Author:Raloff, J.
Publication:Science News
Date:Mar 14, 1992
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