British drug safety officials are poised to issue new HRT warnings after American trials revealed an "unacceptable" additional risk of stroke facing thousands of women.
The American studies, halted more than a year earlier than planned, involved oestrogen-only therapy, taken in this country by many women who have had a hysterectomy to treat menopausal symptoms. As many as 40% of all HRT users in this country may be on the oestrogen-only option.
But the risk of a stroke on the single treatment has now been discovered to be greater than thought. The latest US Women's Health Initiative study suggests oestrogen-only HRT poses the same threat as the combined alternative, an extra eight strokes a year per 10,000 women, up from 21 cases to 29.
However, it also suggests that the single HRT poses no increased risk of breast cancer, a stark contrast to results from trials of oestrogen-progesterone therapy, and contrary to what was suggested in a British study last year. It is a further confusing twist to conflicting messages about HRT.
Several trials over its long-term use have now been stopped, but there are mounting concerns among doctors that too many women are abandoning HRT, when it has been proved to help reduce severe menopausal problems including hot flushes, night sweats and vaginal dryness.
British government watchdogs demanded the adding of stroke warnings to combined HRT products in 2002 and the new findings are likely to mean similar warnings for oestrogen-only drugs.
The Medicines and Healthcare Products Regulatory Agency said yesterday that its advisers would consider the latest findings and the product information would be updated as necessary "and women and doctors will be clearly informed of the new advice".
Increased breast cancer risk from HRT has already prompted the MHRA to advise doctors and women that therapy should be taken for the "shortest duration", at the lowest effective dose, and only to treat menopausal symptoms. Treatment should be reviewed at least annually.
The cancer scare has also helped force the abandonment of HRT as a frontline treatment for the prevention of osteoporosis, a decision that has angered some doctors. The brittle bone condition affects mainly women who are well past the menopause.
Up to 1.7 million women in Britain are thought to be on HRT, but that number may have fallen by up to 30% since the first serious warnings over combined HRT were raised by the US WHI programme in July 2002. Those trials were stopped because increased dangers of breast cancer, strokes, heart disease and blood clots were said to outweigh benefits in preventing colon cancer or hip fractures.
Last August, Cancer Research UK in this country published analyses of 1 million women who has passed through the breast cancer screening programme, of whom around half used or had used HRT. Long-term use of 10 years doubled the risk for combined HRT users and posed an extra 30% for oestrogen-only users.
The dropping of the oestrogen-only trial involving 11,000 post-menopausal women who had had a hysterectomy, was announced yesterday by the National Institutes of Health in the US.
The women, aged 50-79, were either given oestrogen treatment or a dummy pill over as period of nearly seven years. Women who have not had hysterectomies do not traditionally have the single treatment because of a known risk of womb cancer. The US results suggest no increased risk of breast cancer, a different finding from the British study, and no effect either way on heart disease.
Valerie Beral, of the Cancer Research team, said yesterday that the Americans had "stopped their study before they had the statistical power to know".
Wyeth, a big HRT manufacturer, said the women in the US trials started at an average age of 63, far older than most users in Britain and the finding of no increased breast cancer risk was "good news" for oestrogen-only HRT users.
"Many women who require hysterectomy are in their 30s and 40s", said Allison Jeynes-Ellis, the company's medical director in the UK and Ireland. "Menopausal symptoms can disrupt a woman's daily activities at home or at work, interrupt her sleep, contribute to fatigue and affect relationships, making HRT an attractive treatment option."
