Novartis’ breast cancer drug Femara has been approved in the USA for the first-line treatment of early-stage breast cancer, after surgery, in post-menopausal women.

The green light follows a similar approval in the UK last month, which made Femara (letrozole) the only aromatase inhibitor cleared for use across the entire breast cancer spectrum - before surgery, directly post-surgery, after five years of standard tamoxifen treatment and in advanced cancer.

The approval was based on the results of the BIG1-98 trial, which were published in the New England Journal of Medicine on December 29. In the study, Femara was 27% more effective than the long-standing anti-oestrogen drug tamoxifen in preventing metastases in these patients, and 19% more effective in preventing a relapse of breast cancer, although there was no difference in overall survival.

Sales of Femara in the first nine months of 2005 climbed 44% to $390 million, making it the fastest-growing product in Novartis’ oncology franchise. It competes in the aromatase inhibitor sector with AstraZeneca’s Arimidex (anastrozole) and Pfizer's Aromasin (exemestane), which had nine-month 2005 sales of $856 million and $176 million, respectively.

Analysts have said that Femara could see sales in excess of $1.4 billion at peak, driven by new indications.