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Low Rate of Endometrial Abnormalities in Women Taking Tamoxifen
Findings from a new study may ease the minds of women taking tamoxifen for breast cancer, according to researchers at Loyola Medicine. Women with early-stage estrogen receptor-positive breast cancer who took the drug had a low rate of rate of developing endometrial abnormalities, none of which developed into uterine cancer during 5 years of follow up.
The researchers presented their findings at the annual meeting of the American Society of Clinical Oncology in Chicago.
Used to treat breast cancer and also to help prevent it in healthy women at high risk of developing the disease, tamoxifen has been shown to be highly effective, the researchers said.
“However, many women who would benefit from taking tamoxifen fail to do so because they fear getting endometrial cancer,” said study co-principal investigator Ronald K. Potkul, MD, FACS, FACOG, chair of the department of obstetrics and oncology of Loyola University Chicago Stritch School of Medicine. “Our study found that for women who did not have endometrial abnormalities when they began taking tamoxifen, there was a very low rate of developing premalignant conditions.”
Among 89 women who took tamoxifen alone, 5 endometrial abnormalities were discovered at the 2-year point. One abnormality was discovered in another group of 80 women who took tamoxifen plus the hormone progestin. None of the abnormalities—including an additional abnormality discovered 3 years later—developed into uterine cancer by the 5-year point.
Researchers had predicted that combining tamoxifen with progestin would decrease the risk of endometrial abnormalities, but the difference was not large enough to be statistically significant. They also expected 30% of women taking tamoxifen alone would develop endometrial abnormalities by year 2, but just 6% did.
They suspect the study’s screening requirements for participants may have led to the lower abnormality rate. Before taking tamoxifen, women underwent uterine ultrasound exams, and those with a thickening of the inner lining of the uterus greater than 5 mm went on to receive a biopsy. Women whose biopsies showed an endometrial abnormality were excluded from participation in the study.
"For women who are concerned about taking tamoxifen to treat or prevent breast cancer, our study suggests that a normal ultrasound before treatment may provide additional reassurance," said first author of the study Kathy S. Albain, MD, FACP, FASCO, a professor in the department of medicine, division of hematology/oncology, at Loyola University.—Jolynn Tumolo
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