A major HRT trial in the US has been halted because the combination of conjugated equine oestrogen (0.625 mg/ day) and medroxyprogesterone acetate (2.5 mg/day) (Prempro) simply did more harm than good.
The much-touted Women's Health Initiative (WHI) was a randomised, controlled trial designed to prove, once and for all, the many health benefits of HRT. From 1993 to 1998, 16,608 healthy postmenopausal women, aged 50-79 years, were enrolled.
The trial was halted after it was found that the HRT combination increased the risk of invasive breast cancer by 26 per cent, heart attacks and other coronary events by 29 per cent, and stroke by 41 per cent. Women on the HRT also had twice the risk of blood clots compared with those taking placebo.
Most of the adverse outcomes were seen during the first two years, except for breast cancer risk, which did not increase until after four years.
Keen to salvage something from the debacle, the researchers note a 37 per cent reduction in bowel cancer and a 24 per cent decrease in hip fractures. But these same benefits are easily achieved by less harmful changes in lifestyle.
The researchers also suggest that the oestrogen-only pill may still be taken with confidence - a suggestion that flies in the face of the accumulated evidence of the carcinogenic potential of unopposed oestrogen.
Given that the raison d'^etre of HRT treatment is to preserve health and prevent disease in peri- and postmenopausal women, this trial has conclusively proved that HRT does neither (JAMA, 2002; 288: 321-33, 366-8).