Aromatase inhibitors save significantly more post-menopausal women from breast cancer than tamoxifen, according to the findings of a major analysis published today.
Overall the drugs cut death rates by 40% among women with oestrogen-receptor positive breast cancer.
This kind of disease is responsible for 80% of cases of breast cancer among women who have been through the menopause.
The analysis, published in The Lancet, combines the findings of nine trials involving nearly 32,000 women.
The drugs work by eliminating oestrogen from the body.
The researchers found that after taking the treatment for five years, women's risk of dying within ten years was cut by 40%.
This compared with a 30% reduction achieved by taking tamoxifen.
Researcher Professor Mitch Dowsett, of the Royal Marsden Hospital, London, UK, said: "Our global collaboration has revealed that the risk of postmenopausal women with the most common form of breast cancer dying of their disease is reduced by 40% by taking five years of an aromatase inhibitor - a significantly greater protection than that offered by tamoxifen.
"Aromatase inhibitors remove only the tiny amount of oestrogen that remains in the circulation of women after the menopause - but that's enough to have a substantial impact on a wide range of ER-positive tumours, despite their extraordinary differences at the molecular level.
"But aromatase inhibitor treatment is not free of side-effects, and it's important to ensure that women with significant side-effects are supported to try to continue to take treatment and fully benefit from it."
Professor Paul Workman, Chief Executive of The Institute of Cancer Research, London, UK, added: "The evidence on aromatase inhibitors has been accumulating for well over a decade, but it has taken this huge and complex study to make sense of all the data, and provide a firm basis for clinical guidelines."
* A second study in the same journal, conducted by researchers at the universities of Oxford and Sheffield, show how bisphosphonates can help prevent the disease getting into the bones of post-menopausal women.
Nell Barrie, of Cancer Research UK, said: "These two studies give further evidence that aromatase inhibitors and bisphosphonates - both currently available treatments - help prevent breast cancer coming back in women who have been through the menopause."
Overall the drugs cut death rates by 40% among women with oestrogen-receptor positive breast cancer.
This kind of disease is responsible for 80% of cases of breast cancer among women who have been through the menopause.
The analysis, published in The Lancet, combines the findings of nine trials involving nearly 32,000 women.
The drugs work by eliminating oestrogen from the body.
The researchers found that after taking the treatment for five years, women's risk of dying within ten years was cut by 40%.
This compared with a 30% reduction achieved by taking tamoxifen.
Researcher Professor Mitch Dowsett, of the Royal Marsden Hospital, London, UK, said: "Our global collaboration has revealed that the risk of postmenopausal women with the most common form of breast cancer dying of their disease is reduced by 40% by taking five years of an aromatase inhibitor - a significantly greater protection than that offered by tamoxifen.
"Aromatase inhibitors remove only the tiny amount of oestrogen that remains in the circulation of women after the menopause - but that's enough to have a substantial impact on a wide range of ER-positive tumours, despite their extraordinary differences at the molecular level.
"But aromatase inhibitor treatment is not free of side-effects, and it's important to ensure that women with significant side-effects are supported to try to continue to take treatment and fully benefit from it."
Professor Paul Workman, Chief Executive of The Institute of Cancer Research, London, UK, added: "The evidence on aromatase inhibitors has been accumulating for well over a decade, but it has taken this huge and complex study to make sense of all the data, and provide a firm basis for clinical guidelines."
* A second study in the same journal, conducted by researchers at the universities of Oxford and Sheffield, show how bisphosphonates can help prevent the disease getting into the bones of post-menopausal women.
Nell Barrie, of Cancer Research UK, said: "These two studies give further evidence that aromatase inhibitors and bisphosphonates - both currently available treatments - help prevent breast cancer coming back in women who have been through the menopause."
