The Pharmaceutical Journal
Vol 272 No 7298 p569
8 May 2004

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Exemestane better than tamoxifen after initial treatment for breast cancer

POEM series

Clinical question Does exemestane improve outcomes in patients with breast cancer when given two to three years after diagnosis?

Bottom line Exemestane improves outcomes for postmenopausal women with oestrogen-receptor-positive breast cancer when given for two to three years after treatment with tamoxifen for two to three years.

Synopsis Tamoxifen is the current standard of care for the treatment of oestrogen-receptor-positive breast cancer in postmenopausal women. Exemestane is an aromatase inhibitor (ie, blocks the conversion of androgens to oestrogen) and may be superior to tamoxifen in patients with metastatic disease. After two to three years of tamoxifen therapy, patients were randomized to receive exemestane 25mg daily (n=2,380) or tamoxifen 20mg daily (n=2,362) to complete a five-year course of therapy. All of the women were postmenopausal, had normal renal and liver function, and had an oestrogen-receptor-positive primary breast cancer. Allocation was concealed and analysis was by intention to treat. Patients were re-evaluated regularly. The primary outcome was disease-free survival. The number of patients who died, developed contralateral breast cancer, or had disease recurrence was lower in the exemestane group (183 vs 266; 7.8 per cent vs 11.2 per cent; P<0.001). After three years, the likelihood of disease-free survival was 91.5 per cent in the exemestane group and 86.8 per cent in the tamoxifen group (absolute risk reduction 4.7 per cent; number needed to treat for three years 21.3). There were fewer deaths in the exemestane group, but this difference was not statistically significant (93 vs 106). The risk of contralateral breast cancer was lower in the exemestane group (hazard ratio 0.44; 95 per cent confidence interval,0.20–0.98). Exemestane caused more arthralgias and diarrhoea, but fewer thromboembolic events, less vaginal bleeding and fewer muscle cramps than tamoxifen.

Level of evidence 1b (individual RCT with narrow confidence interval).

Reference Coombes RC, Hall E, Gibson LJ, et al. A randomized trial of exemestane after two to three years of tamoxifen therapy in postmenopausal women with primary breast cancer. New England Journal of Medicine 2004;350:1081–92

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