Lifestyle factors like HRT 'don't compound genetic risks' of breast cancer

Hormone replacement therapy and lifestyle choices do not boost the risk of breast cancer in women who have faulty genes linked with the disease, according to a a new study.

Experts had suggested there might be dangerous interactions between genes that increase the risk of breast cancer and other factors such as taking HRT. This would place such women at a particularly high risk of breast cancer.

However, researchers from Oxford University have found this isn't the case meaning people aren't completely at the mercy of their own DNA.

British researchers have found that genetic and lifestyle factors contribute separately to a person's risk of breast cancer and do not interact

British researchers have found that genetic and lifestyle factors contribute separately to a person's risk of breast cancer and do not interact

They studied more than seven thousand women with breast cancer and over ten thousand women without it. All of the women provided a blood sample for genetic testing and information about other risk factors like obesity, alcohol consumption and hormone replacement therapy.

The scientists used a statistical analysis to examine the relationship between genetic and lifestyle factors.

They found that although genetic mutations and lifestyle choices both contribute to cancer, they do so separately and do not mix for a more deadly effect.

The genetic mutations studied are carried in up to 60 per cent of women and increase a woman's breast cancer risk up to a fifth.

The study, published in the medical journal The Lancet, did not include the rare BRCA genes which dramatically increase the risk of breast cancer.

Study author Ruth Travis from the Cancer Epidemiology Unit at Oxford, said it was reassuring she and colleagues didn't find any proof of synergy between breast cancer mutations and lifestyle factors.

'There's a danger of feeling you're at the fate of your genes,' Dr Travis said.

'But whatever you're born with, there are things you can do to modify your risk.'

Experts said lifestyle factors are often more important in avoiding breast cancer than genetic ones. For example, being overweight elevates your risk by 40 per cent while taking hormone replacement therapy doubles it.

Susan Gapstur, vice president of epidemiology at the American Cancer Society, said the research underlined the complexity of breast cancer and that scientists still don't completely understand what triggers it.

'It likely won't be a single genetic factor (that causes breast cancer) but maybe several genetic variants in combination and some environmental factors,' she said.

The latest study was paid for by Britain's Medical Research Council and Cancer Research UK.

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