RESEARCH - Womb cancer risk varies by HRT type

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Womb cancer risk varies by HRT type

Last Updated: 2005-04-29 10:00:18 -0400 (Reuters Health)

NEW YORK (Reuters Health) - Certain types of hormone replacement therapy

(HRT) increase a woman's risk of endometrial cancer, research suggests.

HRT replaces the natural hormones in the body to relieve unpleasant symptoms

of the menopause, such as hot flushes and mood swings.

HRT preparations containing estrogen only increase the risk of endometrial

cancer. To reduce the risk, many women take combined estrogen-progestagen

preparations or tibolone -- a synthetic steroid with hormonal activity.

However, little information exists on the risk of womb cancer in users of

these therapies.

The new study suggests that HRT with estrogen only or with tibolone

increases the risk of endometrial cancer, while the addition of progestagen

counteracts that effect. Tibolone is prescribed in many countries outside of

the US to treat menopausal symptoms.

In the study, Dr. Beral, at the University of Oxford, and colleagues

collected information on HRT use in approximately 720,000 postmenopausal

women who had no history of cancer and had not had a hysterectomy. During an

average of 3.4 years follow-up, 1,320 women developed endometrial cancer.

Compared with women who never used HRT, the risk of endometrial cancer was

highest in women using tibolone and those using estrogen-only HRT. The risk

was lowest among those using continuous combined HRT and was not altered in

women who used estrogen with sequentially added progestin, a treatment

schedule called cyclic combined HRT.

Cancer risk associated with HRT use varied depending on the woman's body

mass index. Among women who were not overweight, the use of tibolone,

estrogen-only, or cyclic combined HRT significantly increased the incidence

of endometrial cancer, and continuous combined therapy conferred no benefit.

Among obese women, who are at higher risk of endometrial cancer than

non-obese women, tibolone and estrogen-only HRT had little effect on risk,

whereas combined HRT significantly reduced the incidence.

The study group points out that the use of combined HRT actually increases

the risk of breast cancer compared with estrogen-only. Since breast cancer

is more common than endometrial cancer, any benefits associated with the

addition of progesterone are outweighed by the risks.

In a related editorial, Dr. Louise A. Brinton and colleagues at the National

Cancer Institute in Bethesda, land, point out that women with persistent

menopausal symptoms may still require HRT treatment.

Therefore, " for these women and their clinicians, continued research on the

long-term risks and benefits of hormone therapy, screening modalities, and

effective risk communication remains an important priority.'

SOURCE: Lancet April 28, 2005.

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