AstraZeneca has been granted approval in several European markets to expand the indications of its Arimidex breast cancer drug to include women with the disease who have already been treated for two to three years with the mainstay anti-oestrogen therapy tamoxifen.

The company said Arimidex (anastrozole) is the first drug in the aromatase inhibitor class to be approved both for primary adjuvant use – directly after breast cancer surgery – and as a follow-on therapy after tamoxifen.

Although Arimidex has become widely used as a primary adjuvant therapy – helping sales of the drug climb by almost a third to $335 million in the first quarter of this year.

But according to Professor Walter Jonat of University of Kiel in Germany, "the question remained whether those patients who did not receive anastrozole from the start of their treatment would still be able to benefit.”

The new indication for anastrozole was granted on the back of data from three studies which revealed that switching breast cancer patients from tamoxifen to anastrozole increased progression-free survival. It has been granted in the EU Mutual Recognition markets: the UK, Germany, Austria, Portugal, Italy and Spain