Increasing the standard duration of treatment with tamoxifen from five to 10 years could prevent up to 1,000 deaths from breast cancer each year.
Researchers at the University of Oxford have found that doubling the time reduces the risk of tumour recurrence and the mortality rate.
Already the most widely used hormonal drug for treatment of breast cancer in remission, tamoxifen could see its market increased by these findings.
The hormonal drug was originally launched by ICI and is now available in various branded and generic formulations.
Tamoxifen is used to treat women with ER-positive breast cancer, which is accelerated by oestrogen – the drug blocks the hormone’s uptake.
The Oxford research group looked at 6,847 women with ER-positive breast cancer, half of whom were given tamoxifen for five years and half for 10 years.
Tumour recurrence occurred in 21.4% of the 10-year group compared to 25% of the five-year group. Mortality from breast cancer fell from 15% of the five-year group to 12% of the 10-year group.
Since more than 40,000 women are diagnosed with breast cancer in the UK, and most of these are ‘ER-positive’, the longer treatment duration could save up to 1,000 lives each year.
The report stated: “Good evidence now exists that 10 years of tamoxifen in ER-positive breast cancer produces substantial reductions in rates of recurrence and in breast cancer mortality not only during the first decade, while treatment continues, but also during the second decade, long after it has ended”
Dr Caitlin Palframan, Head of Policy at Breakthrough Breast Cancer, said: “This trial is great news for women with this type of breast cancer.”
According to Professor Trevor Powles of Cancer Centre London, these findings “should herald a change in practice”.