Research summary
April 2007
Hormone replacement therapy (HRT) and ovarian cancer risk
Summary
Research published in The Lancet has reported that women who use hormone replacement therapy (HRT) are at increased risk of ovarian cancer. The results from the "Million Women Study" conducted in the UK have shown that current HRT users are on average 20 per cent more likely to develop and die from ovarian cancer than those who have never received HRT.
The study found that for every 1000 women using HRT, 2.6 developed ovarian cancer over five years, compared to 2.2 per 1000 in women who had never used HRT. This equates to one extra ovarian cancer diagnosed in every 2500 HRT users, and one extra death from ovarian cancer in every 3300 users.
The researchers found that risk did not differ significantly by the type of HRT preparation used i.e. oestrogen only or combined HRT (oestrogen and progesterone). The risk of ovarian cancer was also found to increase with increasing duration of use. However, after women stop taking HRT, their risk of ovarian cancer returns to that found in women who have never used HRT regardless of duration of use.
National Breast Cancer Centre comment
The results from the "Million Women Study" provide valuable information to build on our existing knowledge about the risk of ovarian cancer associated with HRT use.
The evidence to date has shown there is a small increase in risk associated with long-term use of oestrogen-only HRT. This study shows there is also a slightly smaller but nonetheless an increase in risk with combined HRT.
Although the study shows a significant increase in risk at a population level, it is important to keep this research in context of what it means for an individual woman.
For an individual woman the increase in risk of ovarian cancer associated with HRT use is small. However, women should be aware that there are both benefits and risks associated with the use of HRT. Women who are considering starting HRT should discuss their decision with their GP based on their individual background risk, the severity of menopausal symptoms and the success of other treatments. Women who are currently taking HRT should review their decision over time, in consultation with their GP, as new evidence emerges.
The results of this study do not change current recommendations regarding use of HRT.
For more information about HRT, visit the National Health and Medical Research Council's website.