Research summary
April 2008
Cancer risk persists after ceasing combined hormone replacement therapy
New results from the Women’s Health Initiative (WHI) show that the cancer risks associated with long-term use of combined hormone replacement therapy persist three years after a woman stops taking the drugs.
Background
The Women’s Health Initiative is a major 15-year study involving over 160,000 women. The study is focused on strategies for preventing heart disease, breast and colorectal cancer and osteoporotic fractures in post-menopausal women – the major causes of death, disability and frailty in women.
One component of the study examined the effects of combined hormone replacement therapy (HRT) on the prevention of coronary heart disease and osteoporotic fractures, and any associated risk for breast cancer. This trial was stopped early because of increased risks of cardiovascular disease and breast cancer in women taking combined HRT.
These new findings are a follow-up study of 15,730 post-menopausal women who participated in the initial HRT trial. The study reports on the health outcomes of the trial participants three years after they stopped taking combined HRT.
Research findings
The researchers found that three years after stopping the HRT trial:
- The risk of any type of cancer was 24 per cent higher in women who took combined HRT compared to those who did not take hormones as part of the initial trial.
- Women who took combined HRT were 27 per cent more likely to develop breast cancer than women who did not take hormones. However, this finding was not statistically significant.
- The lower risk of colorectal cancer seen in women who took combined HRT disappeared after stopping the therapy.
- There was no longer an increased risk of cardiovascular disease (heart disease, stroke and blood clots) in women who took combined HRT.
- The benefit in reducing fractures in women who took HRT disappeared after stopping the therapy.
National Breast and Ovarian Cancer Centre comment
This follow-up study confirms that combined HRT should not be used to prevent disease in healthy, post-menopausal women.
For an individual woman the increase in breast cancer risk associated with combined 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 general practitioner 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.
Source
Source: Health risks and benefits three years after stopping randomised treatment with oestrogen and progestin. Journal of the American Medical Association 299(9) 5 March 2008. 1036-45.