HRT breast cancer risk may be lower than researchers thought

A WOMAN’S risk of developing breast cancer while using hormone replacement therapy (HRT) may be lower than people think, researchers said yesterday.

A number of major studies have linked HRT - used to combat menopausal symptoms - to an increased risk of breast cancer and also stroke.

The revelations led many women to abandon treatment due to fears they faced a much greater risk of cancer.

But now, researchers in Australia, writing in the British Medical Journal, have suggested that many women may have stopped taking HRT unnecessarily.

The team from the New South Wales Breast Cancer Institute used the latest data to estimate a woman’s individual risk of developing breast cancer up to the age of 79, taking into account use of HRT - known as “cumulative absolute risk.”

The researchers said that, until now, only population risk data had been available, whereas their own analysis would help doctors weigh up the pros and cons of treatment more accurately.

They found that the cumulative absolute risk of breast cancer declined as the number of years remaining of life during which the disease could develop diminished.

Among women not taking HRT, the average risk for those aged 40-79 stood at 7.2% - one in 14 women developing the disease.

When the researchers looked at the group starting at the age of 50 up to 79, the risk stood at 6.1% (one in 16) and at 60-79 the risk was 4.44% (one in 23).

The researchers said use of HRT increased a woman’s risk of breast cancer, but only slightly. They estimated that, from the age of 50, use of oestrogen-only HRT or short-term use of combined oestrogen-progesterone HRT (around five years) hardly affected breast cancer risk at all.

With no use of HRT, the risk stood at 6.1%, rising to 6.3% for those on oestrogen-only HRT and 6.7% for combined therapy.

Even with extended use, oestrogen-only HRT had a minimal effect on the risk of breast cancer.

A 55-year-old woman not taking HRT had a cumulative absolute breast cancer risk to the age of 79 of 5.3%. Using oestrogen-only HRT only increased this risk by 0.2% after five years of use, 0.5% with 10 years and 0.9% with 15 years.

The researchers did find that combined HRT had a greater extra risk, especially if it was taken for more than five years.

Past research suggests that half of women in Australia, Europe and America taking HRT are using combined HRT.

The researchers pointed out that once HRT was stopped, a woman’s risk of breast cancer quickly returns to that of someone of the same age who has never used it.

They said fears about the risks of HRT had resulted in reduced use in many countries.

“Without individual risk data, however, it is difficult to weigh the benefits and harms of treatment accurately, and many women may have stopped unnecessarily.”

However, the researchers said other women may under-estimate their additional risk and continue taking the drugs.

The Million Women Study, published in 2003, found that using combined HRT doubled a woman’s risk of developing breast cancer compared with women not taking HRT.