Possible test for selection of adjuvant systemic therapy in early cancer of the breast.

The estrogen receptor content and the thymidine labelling index have been correlated in a series of primary cancers of the breast. Receptor was assayed in tumours of 409 patients with operable breast cancer. Recurrence rates were significantly higher in patients whose tumours did not contain receptors than in those whose tumours did. Women without axillary node involvement whose tumours lacked oestrogen receptors showed the same high rate of recurrence as all women with axillary involvement. The oestrogen receptor status of metatases was similar to that of the primary tumours. The thymidine labelling of 83 tumours was inversely related to their receptor content. Tumours without receptors had the highest indices and therefore the highest potential tumour growth. These results have been discussed in relation to selection of systemic adjuvant therapy.