Menstrual Cycle Variation in Mammographic Breast Density: So Who Cares?

Extract

So who cares? Is it really important that there is a 4% excess in the proportion of women with mammographically “extremely dense breasts” in the luteal phase of the menstrual cycle compared with the follicular phase? For that is what White et al. (1) have clearly shown in this issue of the Journal in a study based on an analysis of 2591 menstruating women who had screening mammograms in a health maintenance organization during the last 7 months of 1996.

My opinion is that this excess is important. As White et al. (1) point out, increased mammographic density is associated with decreased mammographic sensitivity and decreased mammographic specificity. Both of these operating characteristics put younger women at a disadvantage compared with older women in terms of benefiting from the early detection of breast cancer. As for the small size of the effect (4% overall), it is often overlooked that a small effect on a large population can have an impact far greater than a large effect on a small population. When millions of women are being encouraged to seek mammographic screening in their forties, even a small effect may prove to be important.