A small study suggests that timing Researchers Investigate Whether Timing of Mammogram Could Influence Accuracy (dateline April 4, 2001) | Breast Health News | Imaginis - The Women's Health & Wellness Resource Network

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Researchers Investigate Whether Timing of Mammogram Could Influence Accuracy (dateline April 4, 2001)

A small study suggests that timing mammograms according to a woman’s menstrual cycle may help improve the accuracy of the exam. According to the researchers, breast tissue is often less dense early in the menstrual cycle, and less density could make it easier to detect breast cancer on mammogram films. However, the American Cancer Society finds limitations to the study and says that having a mammogram is more important than scheduling it to coincide with the early phase of the menstrual cycle.

Breast tissue density shows up as white areas on a mammogram film and this density can eclipse breast cancer, which also shows up as white areas on the film. To determine whether cyclic changes in breast density warrant specific attention to the timing of mammograms, researchers from the University of Southern California Norris Comprehensive Cancer Center examined breast density measurements in 11 healthy women between the ages of 30 and 45.

While the average changes in breast density throughout the women’s menstrual cycles were small (an average of 1.2%), 6 out of the 11 women in the study had significant changes in breast density (between 1.4% and 7.8%). Therefore, the researchers conclude that pre-menopausal women who have annual screening mammograms  may benefit from scheduling the exam during the early days of their menstrual cycle (the week immediately after menstruation). Many physicians already recommend that women with sensitive breasts have their mammograms at this time because the breasts tend to be less tender.

While the American Cancer Society calls the results of the study interesting, the research does not warrant a change in screening recommendations. According to Robert Smith, PhD, Director of Cancer Screening for the American Cancer Society, there are a number of limitations to the study. Of importance, the researchers only examined changes in breast density during the menstrual cycle. They did not examine the accuracy of the mammography performed.

Also, the size of the study was very small: only 11 women participated, none of whom had breast cancer. The average age of the women in the study was 35, despite that fact that annual screening mammograms are not recommended for women under 40 years of age. In general, older women tend to have less dense breast tissue than younger women, especially after menopause when the glandular tissue of the breast is largely replaced with fatty tissue.

Furthermore, four of the women in the study did not experience any changes in breast tissue density during their menstrual cycles. This suggests that the degree of change varies from woman to woman, and thus, the timing of mammography may not provide a benefit for some women.

According to Dr. Smith, it is important that women schedule annual mammograms beginning at age 40. At some facilities, it is necessary to schedule mammograms weeks or months in advance, and it may not be possible to time the mammogram to a woman’s menstrual cycle. This should not deter women from receiving mammograms, said Dr. Smith. However, some women do find the exam to be more comfortable during the early phase of the menstrual cycle.

Mammography detects approximately 85% of all breast cancers and is the only exam approved by the U.S. Food and Drug Administration (FDA) to help detect breast cancer in women with no signs of the disease such as a lump.

Guidelines for early breast cancer detection:

  • All women between 20 and 39 years of age should practice monthly breast self-exams and have physician performed clinical breast exams at least every three years.
  • All women 40 years of age and older should have annual screening mammograms, practice monthly breast self-exams, and have yearly clinical breast exams. The clinical breast exam should be conducted close to and preferably before the scheduled mammogram.
  • Younger women with a family or personal history of breast cancer should talk to their physicians about beginning annual mammograms before age 40.

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