By Alexandra Goho

As Time Goes By...

By Alexandra Goho

In the 1980s, the rate at which doctors diagnosed women with new breast cancers rose dramatically and continued rising throughout the 1990s. Researchers attributed this increase to more women receiving mammograms, which can detect tumors too small to be felt through physical examination. But suddenly, starting in 2003, breast cancer rates began to drop.

A widespread halt in the use of hormone replacement therapy by postmenopausal women is the most likely explanation for the sudden decline, says medical oncologist Eric Winer, of the Dana-Farber Cancer Institute in Boston. Doctors began to take their patients off the drugs after a 2002 study found that women who used hormone therapy had an increased risk of developing invasive breast cancer. Subsequent studies later showed that a drop in the use of hormone therapy after 2002 coincided with a decrease in breast cancer incidence rates.

Some researchers have suggested that the hormones may trigger or hasten the growth of small cancers. If discontinuing hormone use only slows cancer growth, rather than stopping it altogether, incidence rates may eventually rise again as now slower-growing tumors are found.