Reduced HRT may have cut U.S. breast cancer rates: study

The reduced use of hormone replacement therapy (HRT)in 2002 may have produced a sharp drop in U.S. breast cancer rates in 2003,U.S. researchers suggested Thursday.

There was a seven per cent relative decline in breast cancer incidence between 2002 and 2003, which equates to 14,000 fewer cases in the U.S., scientists from the University of Texas M. D. Anderson Cancer Center reported at the San Antonio Breast Cancer Symposium.

But the drop was 12 per cent in women between 50-69 who had been diagnosed with estrogen receptor positive breast cancer —the kind that depends on hormones for tumour growth.

"Something went right in 2003, and it seems that it was the decrease in the use of hormone therapy, but from the data we used we can only indirectly infer that is the case," Peter Ravdin, a biostatistics professor at M. D. Anderson, said in a release.

Hormone replacement therapy is generally prescribed to relieve the symptoms ofmenopause.

"Research has shown that ER [Estrogen Receptor]-positive tumors will stop growing if they are deprived of the hormones," he said. Half the women over 50 using hormone replacement therapy [HRT] in 2002 stopped after a major U.S. study concluded that long-term use of estrogen and progestin, the hormones used in the therapy, significantly increased risks of breast cancer, strokes and heart attacks.

'Remarkable finding'

The idea "makes perfect sense" because hormone replacement therapy had been proposed as a possible factor in the increasing rates of breast cancer, said senior investigator Donald Berry, also a professor at M. D. Anderson. "Now, the possibility that the effect is much greater than originally thought all along is plausible, and that is a remarkable finding."

But the researchers stressed that their results are based solely on population statistics, and they cannot reach any definitive conclusions. "Epidemiology can never prove causation," Berry said, but after looking at other possible causes,the researchers believe that only the drop in the use of HRT explains the decline in the cancer statistics.

Researchers from M.D. Anderson, the National Cancer Institute and Harbor UCLA Medical Center, studied data from nine U.S. regions and found that rates of breast cancer rose from 1990 to 2002. But by the end of 2003, there was a seven per cent decrease.

The Canadian Cancer Society, which keeps track of statistics, saidthat Canadian breast cancer rates are not similarly declining. Therewas a very small dip from 2002 to 2003, but it wasnot dramatic and the overall trend still shows a steady increase in breast cancer.