Anastrozole: new indication. Adjuvant treatment of non metastatic breast cancer: useful for some patients

Abstract

(1) For postmenopausal women with hormone-receptor-positive breast cancer, the reference adjuvant treatment after surgical excision is tamoxifen (an anti-estrogen), taken orally at a dose of 20 mg/day for 5 years. (2) Anastrozole is the first aromatase inhibitor to be licensed for this use in France. (3) Marketing authorisation was based on the short-term results of a double-blind trial comparing anastrozole (1 mg/day) with tamoxifen (20 mg/day) in 9366 women. The trial is planned to last five years. The results obtained after median follow-up of 4 years showed no difference between the groups in overall survival (109 deaths in each group). But first pathological events were significantly less frequent in the group taking anastrozole (13% versus 15%). Note that these results are undermined by a number of methodological flaws, including relatively short follow-up and definition of relapses using an endpoint mixing heterogeneous prognostic factors. (4) Musculoskeletal disorders, fractures (7.1% versus 4.4%) and hypercholesterolemia were statistically more common with anastrozole than with tamoxifen. Women taking anastrozole found their sex lives less satisfactory than women taking tamoxifen. The following adverse events were statistically less common with anastrozole than with tamoxifen: hot flushes (35.0% versus 40.3%), metrorrhagia, venous thromboembolism (1.1% versus 1.8%), ischaemic stroke (1.1% versus 2.3%), and endometrial cancer (3 versus 15 cases at 4 years). (5) In practice, anastrozole may be beneficial for women who cannot use tamoxifen, such as those at high risk of thrombosis. Anastrozole costs ten times more per day than tamoxifen. Tamoxifen remains the reference adjuvant treatment for all other women.