Australians using menopausal hormone therapy (MHT) are twice as likely to develop breast cancer than those who have never used it, says new research.
But once they stop taking MHT - the updated term for hormone replacement therapy (HRT) - their risk diminishes and is the same as for other women.
The findings of the Cancer Council NSW research, published in the International Journal of Cancer, reaffirm the MHT-associated breast cancer risk and are consistent with most international evidence.
"The message to convey is that it's important that women check in with their doctor every six months about the continuing use of MHT, because the risk of breast cancer increases as duration of use increases," the council's Professor Karen Canfell told AAP.
"MHT is effective in reducing menopausal symptoms like hot flushes and night sweats, and for some women these symptoms can really compromise quality of life.
"The findings are a timely reminder that MHT has risks, but it still may be the right decision for women experiencing moderate to severe symptoms."
The research analysed data from 1236 postmenopausal Australian women with breast cancer and 862 who did not have the disease.
Other breast cancer risks, such as family history, were also taken into account to conclude women currently using MHT were twice as likely to develop the disease.
The elevated risk was greater for women taking combined hormone therapy with oestrogen and progestogen when compared with oestrogen-only therapy.
Using data from the study and a recent population survey, Prof Canfell estimated up to half-a-million Australian women were using MHT.
In emphasising recommendations that the medication should be used for the shortest possible time, she noted most MHT users in the study had been taking it for five years or more.
