THS: less endometrial cancer with combined with estrogen alone

Estrogen alone increases the risk of endometrial cancer , while progestins counteract the effect of estrogen on the endometrium in hormone replacement therapy (HRT) combined , according to the results of the Million Women Study (MWS ) study published in the journal " the Lancet " .
The estrogen-progestogen HRT is used to minimize the increased risk of endometrial cancer associated with HRT based on estrogen alone . However, few data are available on the incidence (number of new cases per year ) of endometrial cancer with estrogen-progestogen HRT.

The MWS study followed more than 700,000 postmenopausal British women aged 50 to 64 years , for 3.4 years on average. In total, 45 % of them reported at the time of entry into the study they used HRT , 22% continuous progestogen HRT , 45% cyclic progestogen HRT and 4% of estrogen alone .

Compared with non-users of HRT , the risk of endometrial cancer was reduced by 29% with continuous combined HRT.

However, it was increased by 45% with estrogen alone.

Cyclical combined HRT did not significantly alter the risk .

The authors also point out that the body mass index (BMI , weight ratio of the square of height ) had a significant impact on these associations. Thus, in non-obese women, the adverse effects of estrogen alone were more important , while the beneficial effects of continuous combined HRT were greatest in obese women .

The first data from the MWS were published in August 2003 in the Lancet, showing that combined HRT increased the risk of breast cancer compared to other types of HRT .

"These results create a dilemma for women who have not had a hysterectomy and want to use HRT ," said in a statement from Cancer Research UK , Professor Valerie Beral , director of the epidemiology unit of research organization .

"On one side , the only progestin HRT increases the risk of endometrial cancer , but on the other hand , the estrogen-progestogen HRT cause the greatest increase in breast cancer ."

" As it is much more common than endometrial cancer , combined HRT raise the overall risk of the most important cancer," she says.

For Professor John Toy , medical director of Cancer Research UK, " it is crucial that we understand the effects of drugs on our bodies. We already know the impact of HRT on the risk of breast cancer and now we understand how it can influence the risk of endometrial cancer . "

" We believe that women should take HRT for medical reasons and only for the shortest possible time ," he adds .