HRT Raises Risk of Lobular Breast Cancer
Study ID's type of tumor tied to combined therapy
TUESDAY, Dec. 3, 2002 (HealthDayNews) -- The National Institutes of Health pulled the plug on a massive study earlier this year after women taking combined hormone therapy were found to have an increased incidence of breast cancer.
Now a new study has identified which type of breast cancer may be associated with the combined hormone replacement therapy, or that which includes estrogen and progestin.
Research appearing in the Dec. 15 issue of the journal Cancer finds that women on combined hormone therapy are at an increased risk for lobular breast cancer.
Lobular and ductal breast cancer are two of the more common forms of breast cancer. Although lobular carcinoma is less aggressive than ductal, it has been on the rise since the 1980s. The use of combined hormone replacement therapy increased during the same time period, leading some to speculate that it might be responsible for the increase.
"It's kind of a bad news/good news thing," says Janet Daling, lead author of the study and a professor of epidemiology at Fred Hutchinson Cancer Research Center in Seattle. "[Lobular carcinoma] is a little more difficult to diagnose because you don't pick it up as often on mammograms, but it has a good prognosis. It appears to be highly related to the continuous combined hormone therapy."
Hormone replacement therapy (HRT) is taken by women to relieve symptoms of menopause. While the hormone estrogen is actually responsible for ameliorating hot flashes and vaginal dryness, it also increases the risk of cancer of the uterine lining. Adding progestin to the mix effectively eliminates that risk. HRT is given one of two ways: continuous (meaning every day or almost every day of every month) or sequential (less often than every day).
This study, called the Women's Contraceptive and Reproductive Experiences (CARE) Study, looked at about 4,500 postmenopausal women aged 35 to 64 who had been diagnosed with their first incidence of breast cancer. They were compared to a control group of postmenopausal women who had no history of breast cancer.
In interviews, all the women were asked to recall information on various aspects of their medical history, including type of hormone therapy used, pattern of use, dose and total duration.
Women who used combined hormone replacement therapy for six months to five years were 1.6 times more likely to get lobular carcinoma. Women who used it for more than five years were twice as likely to be diagnosed with the cancer, compared with women who never used it.
The risk was also greater with continuous hormone therapy, or that which is delivered daily for 25 or more days each month. Women on this type of hormone replacement therapy for five years or more had a 2.5 times greater risk of lobular breast cancer. After adjusting for the age at which menopause began, the increase rose to 3.2 times.
Sequential combined hormone replacement therapy was associated with a 1.5 times greater risk for lobular cancer. "There was very little risk with sequential HRT," Daling says.
Dr. Clifford Hudis, chief of the breast cancer medicine service at Memorial Sloan-Kettering Cancer Center in New York City, cautions against giving too much weight to the findings. This latest research was a case-control study in which women were asked to remember details of their history, and there was no actual control over the dispensing of the medication. The gold standard in medical research remains the prospective randomized trial. "This is the highest standard because presumably bias doesn't influence who takes or doesn't take the medicine," Hudis says.
The results of this study apply only to women under the age of 65. Daling has just finished another study looking at women aged 65 to 79 and, in this group, sequential HRT seemed to play a larger role.
Estrogen alone did not appear to affect the risk of breast cancer.
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