The US Food and Drug Administration has granted US drug giant Pfizer clearance to market its cancer drug Aromasin (exemestane tablets) for the adjuvant treatment of early-stage breast cancer in postmenopausal women who have already received tamoxifen therapy.

The approval, which closely follows a regulatory nod in Europe last month, was based on results from the 4,700-patient Intergroup Exemestane Study, which showed that patients switching to Aromasin after two to three years of taking tamoxifen had 31% more protection from cancer recurrence than those on tamoxifen alone.

According to Pfizer, the superiority of this treatment regime was demonstrated so successfully that the American Society of Clinical Oncologists and the National Comprehensive Cancer Network updated their guidelines to support the use of a new switch regimen using Aromasin. "This new approval for Aromasin clearly provides physicians and patients a more effective way of protecting against cancer recurrence compared to the current treatment practice of five years of tamoxifen therapy," commented Dr Stephen Jones, medical director at US Oncology Research in Houston, Texas.

Aromasin was approved in late in 1999 for the treatment of advanced breast cancer in postmenopausal women whose tumours have stopped responding to tamoxifen. For the first quarter of this year, the drug pulled in sales of $55 million, marking substantial growth of 134% over the same period of 2004 [[20/04/05a]]. Approval for use in patients with early-stage breast cancer should boost its performance even further.