Breast density has emerged as an important research area in breast cancer for two reasons:  Dense breasts are a risk factor for breast cancer, and on mammograms dense breasts can mask breast cancers, making some tumors difficult to detect.  Clinical trials of oral tamoxifen have shown that people who have the greatest reduction in breast density also have the greatest reduction in breast cancer risk, noted Banu K. Arun, M.D., of the University of Texas MD Anderson Cancer Center, who is leading a second tamoxifen gel clinical trial.  Participants in this study will apply the 4-OHT gel or placebo gel to the breasts for a year. “We are measuring mammographic breast density and hoping to see a decrease,” said Dr. Arun.

Source:  NCI