Doctors have known that the drug tamoxifen can reduce the chances that women with high risk for breast cancer will develop the disease. But a better test is needed to find out who among the high-risk women would benefit from this preventive treatment and who would not.

An article in a recent issue of the Journal of the National Cancer Institute (Vol. 93, No. 23: 1791-17988) suggests that looking at breast fluid from high-risk women might help. This fluid could be analyzed under the microscope for abnormal cells, much like a pap smear.

Margaret Wrensch, PhD, and colleagues from the University of California at San Francisco and at Los Angeles have been examining breast fluid samples for 30 years. They reported on the follow up of women who were studied from 1972 through 1991.

These women had their breast fluid drawn in a process called nipple aspiration. Not all of the women were able to produce fluid for the test. The researchers determined whether the women later developed breast cancer, by looking at breast fluid.

The researchers were able to obtain and verify follow-up information on about 7,000 women, 400 of whom developed breast cancer. The researchers found that merely obtaining fluid from the women — whether the cells in the fluid were normal or showed serious changes — meant the women had a 50% greater risk of developing breast cancer at some time in the future than if no fluid could be obtained. The researchers did not have an explanation for this.

Even if the cells in the fluid were normal, there was still a 30% increase in the risk of developing breast cancer. If the cells showed either hyperplasia (overgrowth of normal cells) or atypical hyperplasia (the cells were abnormal but not yet cancerous), the risk was double that of women who produced no fluid.

For women who had a family history of breast cancer, the finding of hyperplasia in breast fluid increased breast cancer risk almost 3½ times. If atypical hyperplasia was seen in the cells of the breast fluid, the risk was increased 4½ times, compared to women without a family history.

The authors said that women younger than 55 years most readily produce breast fluid, and that is the group they believe should be selected for this procedure. They also suggested that if a woman had hyperplasia or atypical hyperplasia in breast fluid, and had previously had a benign traditional surgical breast biopsy, then there is a strong suggestion she is at higher risk.

In an editorial about the article in the same issue (Vol. 93, No. 23: 1762-1763), Carol Fabian, MD, and Bruce Kimler, PhD, from the University of Kansas Medical Center in Kansas City, Kan., urged caution in introducing these procedures into clinical practice.

They said that atypical hyperplasia appears to be associated with an increased short-term risk of developing breast cancer. However, these doctors are unsure if women whose breast fluid contains only normal cells, or those who don’t produce any breast fluid at all should get treatment, even if they are otherwise considered at high risk.

Recent reports indicate that better techniques, such as ductal lavage are available to obtain breast fluid samples.

Careful study of the women undergoing these procedures may provide important information to help lower the number of women who get breast cancer.

According to the American Cancer Society, breast cancer is the most common cancer among women, other than skin cancer. It is the second leading cause of cancer death in women, after lung cancer.

Breast cancer death rates declined significantly from 1992 to 1996, with the largest decrease in younger women — both white and black. This decline is probably the result of earlier detection and improved treatment.