Abstract
Oestrogen receptor determinations were done in metastatic breast cancer tissue of patients with advanced breast cancer. In 37 patients with progressive disease evaluation of the response to endocrine treatment was possible, following the criteria of the E.O.R.T.C. Co-operative Breast Cancer Group. In 20 patients with receptor-negative tumours two objective remissions were noted; in 17 patients with receptor-positive tumours 14 objective remissions were seen. There seems to be a striking correlation between the presence or absence of oestrogen receptor in tumour tissue and the clinical response to hormonal therapy.