Breast Pump Helps Signal Cancer Risk

Noninvasive technique finds clues in nipple fluid

TUESDAY, Dec. 4, 2001 (HealthDayNews) -- A variation of the breast pump could help doctors determine which women are at increased risk of breast cancer by catching telltale tissue changes that presage the disease well before it would otherwise appear.

Scientists in San Francisco say women with any fluid at all, and especially those with abnormal cells in the samples, are likelier to develop breast cancer in the coming years. The fluid can be easily gathered with a modified pump like the kind women use to extract milk, although not all women produce breast fluid when they aren't lactating. A report on the pump study appears in the latest issue of the Journal of the National Cancer Institute.

"I think it needs to be used with caution, but the nice thing about it is it's quick, it's inexpensive, it's well tolerated, and one could conceivably do this at any doctor's office," says Bruce Kimler, a radiation oncologist at the University of Kansas Medical Center in Kansas City.

Kimler, co-author of an editorial accompanying the journal article, says the method isn't meant to take the place of mammography or other diagnostic tools, but rather to give doctors insight into which women are likely to undergo cancerous breast changes in the relatively near future.

"What we're looking for is a state, and that state is associated with multiple changes that could end up as breast cancer," he says.

The American Cancer Society projects that 192,000 women will be diagnosed with invasive breast cancer this year, and more than 40,000 will die from the disease.

Because the overwhelming majority of breast cancers begin in the organ's milk ducts, oncologists have tried to search for early signs of renegade cells in the fluid that washes through the channels. Although precancerous changes appear quite early, tumors typically don't grow large enough to be detected by hand or mammography for about a decade, experts say.

Ductal lavage is one new technique to scour breast fluid for the first warnings of cancer. However, this approach requires local anesthesia and a needle to draw the liquid and is currently recommended only for women at high risk of tumors, for instance, those with a strong family history of the disease or who carry BRCA gene mutations.

But breast pumps can also obtain duct fluid. In an earlier study, scientists at the University of California at San Francisco showed that women with varying forms of abnormal cells in nipple fluid, or aspirate, gathered from pumps were between 2.5 and 4.9 times more likely to develop breast cancer than women who didn't produce enough fluid to measure.

The latest work, led by UCSF epidemiologist Margaret Wrensch, extends that study, which included more than 3,600 non-lactating women since the 1970s. It adds results from another 3,200 women from whom fluid samples were taken between 1981 and 1991. Both groups were followed through March 1999.

Forty percent of women in the two pools didn't pump nipple aspirate on three attempts. But those who did were about 50 percent more likely to develop breast cancer.

What was in the samples was even more revealing. The presence of normal cells in aspirate elevated the risk of cancer by 30 percent over those who didn't produce fluid. And if the cells were abnormal, the odds of developing breast cancer during follow-up, which lasted as long as 27 years, were twice that for women with dry nipples. Women with abnormal cells in aspirate were about 60 percent more likely than those with normal cells to go on to develop breast cancer.

Overall, 7.8 percent of the women in the original group, and 3.5 percent of the later additions, got breast cancer by the end of the study. Such low numbers indicate why even a positive fluid test shouldn't precipitate more than watchful waiting, Kimler says.

"Cells that are just abnormal that are collected in aspirate fluid does not mean that there is anything else there now," he says.

The California scientists admit that needle aspiration may cast a wider net for breast cell changes that pumps miss when women don't secrete fluid. On the other hand, they say, the needle approach is invasive, more likely to cause complications, and is less amenable to mass use.

"We strongly support the efforts of clinical investigators to find applications for this easy-to-perform, noninvasive procedure," they write.

George Casale, a cancer researcher at the Epply Institute at the University of Nebraska Medical Center in Omaha, is hoping to improve on the analysis of nipple aspirate. Casale has been developing a cloned protein, called an antibody, that has an immune reaction to a form of estrogen in breast fluid. The hormone is believed to play a role in the formation of sporadic, as opposed to inherited, breast cancers, which make up 95 percent of all such tumors.

"If this works the way I hope it works, it would be far, far more accurate than mammography," Casale says. What's more, it could have the power to detect breast cancer at its earliest stages, whereas mammography can only find tumors that are large enough to show up on X-rays.

What To Do

To find out more about breast cancer, try the National Cancer Institute or the Centers for Disease Control and Prevention.

For more on ductal lavage, try Johns Hopkins University.

SOURCES: Interviews with Bruce Kimler, Ph.D., professor of radiation oncology, University of Kansas Medical Center, Kansas City; George Casale, Ph.D., research associate professor, Epply Institute, University of Nebraska Medical Center, Omaha; Dec. 5, 2001, Journal of the National Cancer Institute
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