The last major component of a landmark clinical trial investigating the effects of hormone replacement therapy has been terminated a year ahead of schedule because of a slightly increased risk of strokes, the National Institutes of Health announced today.
The trial part of the federally funded Women’s Health Initiative also showed that taking estrogen did not lower the risk of heart attacks. This was a primary reason for undertaking the trial in the first place, said Dr. Barbara Alving, director of the Women’s Health Initiative at the National Institutes of Health.
The announcement is more bad news for hormone replacement therapy. It follows the abrupt termination in 2002 of a larger segment of the Women’s Health Initiative in which women with uteruses took both estrogen and a second hormone, a progestin.
That trial was halted after a safety monitoring board concluded that taking the two drugs conferred more risk than benefit. The hormone combination slightly raised risks for strokes, breast cancer and in the early years heart attacks, while slightly lowering the risk of fractures and colorectal cancer.
In the estrogen-only trial of 11,000 women who lack uteruses, risks for breast cancer and heart disease were not detectably raised over the average of seven years that women took the hormones. Fracture rates were slightly reduced.
However, preliminary data suggest that the risk for dementia and other cognitive decline was also slightly raised in women taking estrogen compared with those taking a placebo.
Experts said that the new findings, which will be published in detail within two months, further weaken the rationale for women taking estrogen, with or without progestin, except for a short period around the time of menopause to treat symptoms such as hot flashes.
But they noted that the risks are slight, and that women do not need to rush to abandon the therapy. They should first consult with their doctors before deciding.
“Hormone replacement, including either estrogen and estrogen plus progestin, still has a place in the treatment of symptoms,” said Dr. Diana Petitti, director of research for Kaiser Permanente Southern California. “But as a global preventive agent, as an agent for preventing coronary heart disease, I think both drugs are on terminal life support.”