WOMEN who have had breast cancer have been shown by a study to be nearly four times more likely to have the disease again if they take hormone replacement therapy. The trial was halted because the women being studied were at such a risk.

The trial, called Habits (Hormone Replacement Therapy after Breast Cancer Diagnosis — is it Safe?) was intended to test the safety of HRT in women who had suffered from breast cancer and had been treated successfully. It is a particularly important issue because treatment for breast cancer can bring on an early menopause.

Women from Sweden, Norway, Switzerland and Denmark were recruited for the trial, which began in 1997. The aim was to enrol 1,300 women. In fact, only 345 were recruited. One group was given HRT for two years; the other was not. The aim was to follow them up for an average of five years.

But by the end of last year, when the average follow-up was only two years, of the 174 women on HRT, 26 had suffered a recurrence of the disease, developed cancer in the other breast, or developed cancer elsewhere. Of the 171 women in the control group, not given HRT, only 7 suffered such recurrences. The difference was such that the committee running the trial was obliged to halt it, and urge the women taking HRT to stop.

Lars Holmberg, from University Hospital in Uppsala, Sweden, the chief investigator, said online in The Lancet: “The Habits trial was terminated because women with a history of breast cancer allocated to receive HRT for menopausal symptoms experienced an unacceptably high risk of breast cancer compared with breast cancer survivors allocated to treatment without hormones.”

A similar trial had begun in Stockholm at about the same time. Since both trials found it hard to get participants, in 2002 the two were combined.

The Stockholm trial had shown much more positive results than Habits, with some evidence that HRT might protect against breast cancer. But when data from the two trials were combined, the net effect was negative. As a result, both trials have been abandoned.

In a commentary in The Lancet, Rowan Chlebowski, from the Harbor-UCLA Research and Education Institute in California, and Nananda Col, from Brigham and Women’s Health Hospital in Boston, say that the results can reasonably be used by clinicians to decide whether to recommend HRT to breast cancer survivors, but that in the absence of HRT there is not much that can be offered for menopausal symptoms: “Alternative strategies for the difficult problem of menopausal symptoms in these women need to be developed.”

Delyth Morgan, of Breakthrough Breast Cancer, said: “Relief of menopausal symptoms poses a real dilemma for women who are successfully treated for breast cancer.

“Although we know that HRT increases the risk of breast cancer, its impact on recurrence is unresolved.” She said that the small study contributed to knowledge of the matter. “However, the results of larger trials under way in the UK and Europe need to be seen before conclusions about HRT use in breast cancer survivors are established.”

Pamela Goldberg, of Breast Cancer Campaign, said that in Britain women with breast cancer were not normally given HRT: “BCC advises women not to come off HRT without discussing it with their doctor.”

Malcolm Whitehead, of the Amarant Trust which gives advice on HRT, said: “We need the Stockholm data as well as the Habits data, and we need to look for differences in study design that might explain the results.” Mr Whitehead, a gynaecologist, noted that only about 20 per cent of the women on HRT in the Habits trial were taking tamoxifen, a breast cancer drug that blocks the effect of oestrogen that can fuel the disease. “I think these results have been published prematurely,” he said. “We need to clarify the situation regarding tamoxifen use.”

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