Therapeutic effect of tamoxifen related to estrogen receptor level.

Cytoplasmic oestrogen receptor (ER) determinations were performed in 59 postmenopausal patients with metastatic breast cancer. Fifty percent of the patients were found to be ER+. Forty patients were treated with tamoxifen (TAM) and 19 patients were treated with tamoxifen plus medroxyprogesterone acetate (MPA). The response rate of TAM-treated patients was 30% (12/40). Of the 21 ER+ patients, ten (48%) responded to therapy. The ER values of these patients were significantly higher than the ER values of nonresponders (P less than 0.01). No correlation could be found between the ER value and the duration of remission in TAM-treated patients.