THURSDAY, March 24, 2005 (HealthDay News) -- Hormone replacement therapy may make it hard to detect breast cancer among postmenopausal women because it can increase breast density, a new study suggests.
Breast imaging experts who rely on magnetic resonance imaging (MRI) for the early detection of breast lesions and malignant tumors say this critical technology can be thrown off by density increases in fibrous tissue among women taking hormone replacement therapy (HRT) -- perhaps leading radiologists to make false-positive readings.
"Women going for an MRI who are on hormones need to let the radiologist know that they are taking the hormone replacements so the radiologist is aware of the potential impact," said study co-author Dr. Priscilla J. Slanetz.
For nearly a quarter century, HRT has been commonly prescribed for the relief of postmenopausal symptoms such as hot flashes, insomnia, mood swings and weight gain.
This latest report, however, is more bad news for a medical regimen that took a big blow in 2002 when a major U.S. study of hormonal therapy -- the Women's Health Initiative -- was halted after early results indicated HRT can increase the risk for heart attack, stroke, blood clots and breast cancer.
The new findings appear in the March issue of Radiology.
Between 1999 and 2000, researchers from Massachusetts General Hospital, Harvard Medical School and Caritas St. Elizabeth's Medical Center in Boston teamed up with French researchers to review MRI breast exams of 60 postmenopausal women aged 44 to 77.
Medical interviews revealed that 29 of the patients were either taking HRT at the time of the study or had done so at some point in the past. An additional eight patients reported taking selective estrogen receptor modulators (SERMs) -- such as raloxifene -- which can function as estrogen-free alternatives to traditional HRT. The remaining 23 patients had never taken either HRT or SERMs.
The team found that breast tissue density tended to be significantly higher among women taking HRT when compared with both women taking no therapy and women taking SERMs. As many as 30 percent of postmenopausal women who take HRT might experience such density increases, the researchers noted.
The study authors warned that increases in breast density could lead to an increased risk for the development of breast cancer among patients taking HRT by making malignancies more difficult to detect in MRI readings.
The researchers did not, however, establish how long a patient would have to be taking HRT before such breast density increases would develop. Nor did they determine how long women would have to wait after discontinuing HRT before breast density levels might drop off.
"It's not a surprise that hormones increase breast density," said Slanetz, who is director of breast imaging at St. Elizabeth's. "But it's another factor that needs to be taken into consideration because it may impact on the ability of a radiologist to interpret the MRI."
However, Slanetz stressed that this finding should not be interpreted as any kind of death knell for HRT.
"This is by no means a message that women should not take hormone replacements," she said. "Women currently taking hormones probably do have a real quality-of-life reason for taking them. That said, it's simply important to know when a woman is taking HRT so I can properly read their MRI."
Study co-author Dr. Daniel Kopans, director of breast imaging at Massachusetts General Hospital, concurred. "I'm not a supporter of hormones, but I don't think we should scare women to not use hormones because of MRIs," he said. "Some women are so devastated by the effects of menopause that their lives are ruined. So it's a balancing act. The discussion should be one between her and her gynecologist."
Dr. Anthony Grieco, a staff physician in obstetrics and gynecology at the Ochsner Clinic Foundation in New Orleans, saw the issue in similar terms. "HRT is still necessary to get some women through the really tough symptoms of menopause," he said. "So there's a utility to HRT."
But he suggested that women on HRT who have the luxury of time might choose a compromise before undergoing an MRI. "If you do need a radiological study like an MRI then go off HRT temporarily -- for at least a month," advised Grieco. "Then go back on HRT if the MRI findings are negative or until the breast problem can be further evaluated."
To learn more about breast cancer, visit the American Cancer Society.