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Detecting Breast Cancer More Difficult in Women Taking Hormone Replacement Therapy

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A study found that women taking HRT (hormone replacement therapy) with both estrogen and progesterone -- called combination HRT -- were more likely to have an abnormal mammogram than women not taking combination HRT. Combination HRT also makes it harder for doctors to read annual screening mammograms. In other words, doctors have hard time deciding whether or not the mammogram shows breast cancer. Other research has shown that HRT increases breast cancer risk.

In this study, 35% of women taking combination HRT had an abnormal mammogram. In comparison, 23% of women who weren't taking combination HRT had an abnormal mammogram. The different rate of abnormal mammograms was found the whole time the women were taking combination HRT and continued for a year after they stopped taking it.

This study, called the Women's Health Initiative (WHI), is very large; thousands of women participated. Other results from the WHI have helped doctors understand the link between using HRT and increased breast cancer risk.

The researchers didn't explain why reading mammograms was harder in women taking combination HRT. It could be doctors were more suspicious and less confident of reading these mammograms because of the higher breast cancer risk associated with taking HRT.

If a screening mammogram is questionable, doctors usually order more testing, such as another mammogram or a biopsy, to help them figure out if cancer is present. Compared to women not taking HRT, women taking combination HRT were 35% more likely to get an extra mammogram and 23% more likely to have a breast biopsy because the initial mammogram had abnormal results.

Even though the initial mammogram was classified as abnormal, many of the women didn't have breast cancer. The researchers considered the additional tests "unnecessary," even though there were good reasons for them. By taking HRT for 5 years, the researchers estimated that a woman has a 10% risk of having an unnecessary mammogram and a 4% risk of having an unnecessary biopsy.

The side effects of menopause can dramatically reduce quality of life for some women. These women have to weigh the benefits of HRT against the risks. If you're having severe menopausal side effects and are considering HRT, talk to your doctor about how you can minimize your breast cancer risk. Be sure to discuss the pros and cons of different types of HRT. Estrogen-only HRT appears to increase breast cancer risk less than combination HRT. Based on the study reviewed here, you might want to ask your doctor about how HRT might affect the reliability of your routine mammograms and the potential need for follow-up testing.

If you do decide to take HRT, try to use it for the shortest time possible. One study found that breast cancer risk was not significantly increased when combination HRT was used for fewer than 3 years. Together, you and your doctor can decide if HRT or another treatment for menopause might be right for you.

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