To gauge estrogen’s effect on mammograms, the UW researchers tracked the experiences of nearly 8,800 participants in a breast-cancer screening program in western Washington state. The results, published in the May 15 Journal of the National Cancer Institute, suggest that when women over 50 take estrogen, with or without progesterone, they’re 71 percent more likely than nonusers to get false reports of possible tumors, prompting needless anxiety and additional testing. The study was too small to measure the danger of real tumors being missed by mammography. But the researchers note that five of the seven study subjects whose tumors went undetected were current or former estrogen users.
For women at special risk of breast cancer, the new findings could take some of the shine off estrogen-replacement therapy. But for most women, the benefits still vastly outweigh the risks. The hormone provides such a strong shield against heart disease and osteoporosis that experts say it would extend life expectancy even if it made mammography useless.
