June 1, 2000 SEATTLE (AP) - Use of a hormone-replacement therapy with estrogen and progestin can more than double the risk of a form of breast cancer, researchers reported today in the journal Cancer.
Scientists at the Fred Hutchinson Cancer Research Center studied 537 King County women at least 50 years old who had breast cancer from 1988 to 1990. They were compared with 492 women who had not had the disease.
Scientists found a 2.6-fold higher incidence of lobular breast cancer in women who took the combination therapy for at least six months and an average of four years.
The reason only one form of cancer increased is "a question for the future: Do some women have certain characteristics that make them more susceptible to lobular cancer when using replacement therapy?" said Dr. Christopher Li, the study's lead author.
About 85 percent of invasive breast cancer cases are in the ducts that carry milk to the nipple. Lobular cancer occurs in the milk-producing lobules and affects about 10 percent of breast-cancer cases.
About 8.6 million women in the United States take the combination therapy treatment and 12 million take estrogen alone.
The hormones reduce the risk of broken bones from osteoporosis and ease menopausal symptoms. In women who have not had a hysterectomy, progestin is used to lower the risk of endometrial cancer.
Earlier studies, including two this year, indicated a heightened risk of breast cancer among women using combination hormone therapy for at least five years but not among those using estrogen alone.
In a related study, Li found a 35 percent increase in lobular cancer between 1988 and 1995.
"Although preliminary, our studies suggest that the incidence of lobular breast cancer is increasing nationwide and that the use of postmenopausal hormone replacement therapy, specifically the use of combined estrogen plus progestin preparations, may be contributing to this increase," Li said.
He said more studies were required to confirm the findings.
Copyright 2000 The Associated Press. All rights reserved.
