Quantitative oestrogen and progesterone receptor values in primary breast cancer and predictability of response to endocrine therapy

The concentrations of oestrogen receptors (ER) and progesterone receptors (PgR) were measured in the tumours from 47 patients with advanced primary carcinoma of the breast who were immediately treated by endocrine therapy after confirmatory histology. All patients were followed-up for at least 3 months and 27 patients for 18 months. The ER and PgR content in their primary tumour was correlated with the response to treatment, the duration of remission and the survival rate. The actual concentrations of ER and PgR were found to be better indicators of endocrine responsiveness than the mere presence of these receptors, particularly in the postmenopausal group. The remission rate improved with increasing concentrations of ER but not with increasing concentrations of PgR in the primary tumour. The predictability was enhanced when ER and PgR concentrations were considered together. Patients with ER concentrations above 150 fmol/mg cytosol protein and PgR concentrations above 100 fmol/mg cytosol protein in the same tumour were in remission after 18 months of treatment. At this time, only two of the 14 patients with ER and PgR concentrations below these levels were in remission and six had died of the disease.