For many women with breast cancer, tamoxifen, a drug that inhibits the hormone estrogen, can be a lifesaver.  

The medicine has been used for decades to fight breast cancers that need estrogen to grow--about 75% of all breast cancers. Unfortunately, breast cancer cells can sometimes become resistant to tamoxifen, a dismal development for patients.

How do the cancer cells do it? Sherene Loi of the Peter MacCallum Cancer Centre in Australia is looking for the genes that underlie tamoxifen resistance.

Post menopausal women who take hormones for more than five years to relieve symptoms such as hot flashes have twice the risk of developing breast cancer as women who do not take estrogen and progestin to replace their own dwindling supplies, according to a new analysis of over 16,000 post-menopausal woman. The women were all in a 15-year study that was halted more than three years early in 2002 because of a clear link between the hormone replacement therapy (HRT) and the disease.

Researchers reported Saturday at the San Antonio Breast Cancer Symposium in Texas that taking HRT for just two years also hikes the odds of developing the disease. But the good news is that the risk dips when the women go off the drugs. The new data comes from a the Women's Health Initiative, a study launched by the National Institutes of Health in 1991 to gauge the effects of the hormone therapy and other factors on heart disease, bone fractures, and breast and colorectal cancer.  There had been earlier studies showing that HRT might prevent osteoporosis (bone-thinning ) and protect the heart. Researchers, however, abruptly stopped the study after finding that it did not guard against heart disease and that there was a 26 percent higher risk of breast cancer among the women taking hormones.

Doctors know that women who have dense breasts have as much as six times the risk of breast cancer as those who have less dense breasts. But they haven’t been quite sure why.

New research presented today at the San Antonio Breast Cancer Symposium offers possible clues: Biopsies of healthy women showed differences in the cells of dense and nondense tissue that may contribute to the development of tumors.

Mayo Clinic docs performed mammograms and biopsies on 60 women ages 45-85 with no history or symptoms of breast cancer. Data that's come back from about half of them showed that dense breast tissue was composed of 6 percent epithelial cells, which line the milk glands and ducts, compared to just 1 percent in the nondense tissue. Some 64 percent of the dense tissue was made up of stroma, or connective tissue, compared to 20 percent in the nondense tissue. And dense tissue was comprised of 30 percent fat, versus 80 percent in nondense tissue.

Voters know a little bit more about Republican vice presidential nominee Sarah Palin’s health as they head to the polls today. According to a two-page letter released by her physician last night, Palin, 44, is in "excellent health and has no known health problems that would interfere with her ability to carry out the duties and obligations of vice president of the United States." 

Until now, Americans knew next to nothing about Palin’s health, other than that she gave birth to five children, the youngest of whom was born with Down Syndrome in April. (People with Down Syndrome have an extra copy of chromosome 21, and have mental and sometimes physical deficits, including heart abnormalities.) According to Palin's doctor, Cathy Baldwin-Johnson, the births were the only time the veep wannabe has been hospitalized.