Women with the most common form of breast cancer enjoy massive long-term benefits from taking the powerful drug, Tamoxifen, for an extended period, British researchers revealed last night.
A major UK-backed study has shown long-term use of the drug may halve deaths from the disease in the second decade after diagnosis.
The study, reported in The Lancet, studied the effect of extending Tamoxifen treatment from five years to ten years, monitoring women for the decade after they stopped treatment.
Nearly 7,000 women took part in the Atlas trial backed by Cancer Research UK and the UK Medical Research Council.
The women were treated for oestrogen receptor positive breast cancer or ER plus cancer, the form that affects about 75% of patients in the UK.
About half took the drug for the recommended five years and the other half were randomly assigned to take it for another five years. The women were tracked for an average of 18 years after they began treatment.
The study found small improvements in the women’s condition in the second five years after treatment through extending drug treatment.
The researchers found extended treatment cut death rates by about 30% after it was stopped. Five years of tamoxifen has already been shown to cut death rates by a similar amount, suggesting that ten years of treatment was responsible for halving long-term death rates, the researchers say.
Researcher Dr Christina Davies, of Oxford University, UK, said: "Around three-quarters of all UK women with breast cancer have hormone sensitive disease, and ATLAS shows that ten years of Tamoxifen helps save lives not just during the decade women are taking the drug, but also during the second decade after diagnosis.”
Martin Ledwick, of Cancer Research UK, added: "Although treatment for hormone receptor positive breast cancer has become more complex in recent years with some women receiving aromatase inhibitors, these results will help in deciding the length of treatment for women who are prescribed Tamoxifen alone."
Davies et al. Long term effects of continuing adjuvant tamoxifen to 10 years versus stopping at 5 years after diagnosis of oestrogen receptor-positive breast cancer: ATLAS, a randomised trial. Lancet 5 December 2012 [abstract]
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