Mammograms accurate throughout menses

CHICAGO, Nov. 29 (UPI) -- Changes in breast density during a woman's menstrual cycle aren't sufficient to impair the accuracy of mammograms, according to a new study.

Mammography is an established screening tool for breast cancer, but dense breast tissue can obscure small tumors and thereby lower the chance a tumor will be detected if present, said Victoria J. Edmond of Indiana University School of Medicine in Indianapolis. Using hormone replacement therapy tends to increase breast density, so some researchers have wondered if normal monthly hormonal fluctuations might also change breast density.

In a small study of 50 premenopausal women, Edmond and her colleagues report that there are no significant differences in the density of a woman's breasts during her menstrual cycle. They took mammograms of each woman's left breast 10 to 13 days after her period began and -- calculating back from the woman's expected menses -- again 2 to 5 days before menstruation. There were no significant differences in breast density between the two mammograms according to two radiologists who were not aware of the timing of the mammograms. In addition, a computerized evaluation of the percent of dense breast tissue measured on a digitized image showed no significant differences, Edmond reported at the annual meeting of the Radiological Society of North America.

Therefore, "timing of a woman's mammogram based on phase of menstruation should not improve sensitivity" of the screening, she said.

Breast density is just one of many things that affect the timing of mammograms, said Mark A. Helvie, director of the division of breast imaging at the University of Michigan in Ann Arbor. For example, many women report that their breasts are less tender in the week or so immediately following menstruation, so mammograms may be more comfortable during that time period. In addition, if a mammogram follows a period, possible pregnancy-associated changes in breast density can be ruled out.

However, none of these factors may make that much of a difference, Helvie told UPI. "The reality of most sites is that you schedule screening mammograms a year or so out, and most women find it impossible to predict [menses] that far in the future."