Efficacy

The proportion of patients who respond to tamoxifen depends on the characteristics of the tumour:

• 30% of all patients with breast cancer respond to tamoxifen
• 50% of patients with tumours which express the oestrogen receptor will respond
• 15% of patients with tumours which do not express the oestrogen receptor will respond

The efficacy of treatment varies with respect to pre- and post- menopausal women.

• pre-menopausal adjuvant therapy with tamoxifen - results in a 12% reduction in annual risk of recurrence and 6% reduction in mortality.
• post-menopausal adjuvant therapy with tamoxifen - results in a 29% reduction in annual risk of recurrence and a 20% reduction in annual risk of mortality.

Bulbrook (BMJ editorial, 1996) suggests that more than five years' adjuvant therapy is not warranted because continuation of tamoxifen treatment would be unlikely to result in clinical benefit.