Beneficial effect of adjuvant tamoxifen therapy in primary breast cancer patients with high oestrogen receptor values.

Oestrogen receptor concentrations were measured in primary tumours of 291 postmenopausal breast cancer patients with high risk of recurrence. These patients were a subset of the 1650 patients participating in the Danish Breast Cancer Cooperative Group's trial of adjuvant treatment with tamoxifen (30 mg daily for one year). A cut-off point of 10 fmol/mg cytosol protein and the use of a Cox proportional hazards model distinguished between patients with long recurrence-free survivals and those with early recurrent disease. The use of this model also showed that patients with an oestrogen-receptor content below 100 fmol/mg did not benefit from the endocrine therapy, while those with concentrations above 100 fmol/mg had a significantly longer recurrence-free survival. This finding is consistent with the response of advanced breast cancer to endocrine treatment.