Further evidence that hormone-replacement therapy can increase a womans risk of breast cancer was reported yesterday by Seattle scientists.
Researchers at the Fred Hutchinson Cancer Research Center studied 537 Seattle-area 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.
Women who took an estrogen-progestin combination therapy for at least six months, and for an average of four years, had a 2.6-times higher incidence of a particular form of this malignancy known as lobular breast cancer.
While other studies have shown that hormone-replacement therapy can increase a womans risk of breast cancer, the Fred Hutchinson findings raised the question of whether the use of these hormones make some women more susceptible to this more uncommon type of breast cancer.
About 85 percent of 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.
An estimated 8.6 million women in the United States take the combination therapy treatment, and 12 million take estrogen alone. Hormone therapy reduces the risk of broken bones from osteoporosis and eases menopausal symptoms.
In women who have not had a hysterectomy, progestin is used to lower the risk of endometrial cancer.
Earlier studies have reported this higher risk of breast cancer among women using combination hormone therapy for at least five years but not among those using estrogen alone.
The Fred Hutchinson study, directed by Dr. Christopher Li, also showed that even some women who took hormones for a short period of time may be at higher risk.
"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.