Aromatase inhibitor letrozole could reduce the risk of breast cancer recurrence in women one to seven years after tamoxifen therapy.

Women originally involved in the placebo arm of an international trial of letrozole showed reduced breast cancer recurrence by one half compared to participants who had never received letrozole, DGDispatch reports.

Risk of metastasis was 60 per cent lower with letrozole, with risk of new tumours development decreased by more than 80 per cent.

An original trial tested whether letrozole could reduce tumour recurrence and increase survival in breast cancer patients who had received five years of tamoxifen treatment.

In October 2003 the study was stopped after interim data analysis showed that tumours of women taking letrozole were significantly less likely to recur.

The latest study analysed data of 2,300 participants, including 1,500 women from the placebo group and 800 who chose no additional treatment.

Three years after the first trial was stopped and letrozole was offered, patients receiving letrozole therapy showed a two per cent risk of the tumour recurring, compared to five per cent in women who chose no treatment.

"It appears that oestrogen-sensitive tumours remain hormone dependent and that patients' survival can be improved with careful use of aromatase inhibitors, even many years after completing tamoxifen treatment," lead author Paul Goss stated.

"These results can be put into practice right away to improve the outlook for women treated for receptor-positive breast cancer."

Authors noted that the study is limited as participants were not randomly assigned, but chose whether or not to take the drug themselves.

The findings will appear in the Journal of Clinical Oncology

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