Variations in estrogen and progesterone receptor levels after short-term tamoxifen treatment in breast carcinoma.

The modification of estrogen and progesterone receptor status was prospectively studied in mammary carcinoma after short-term (7 days) administration of tamoxifen citrate (30 mg/day). Seventeen patients fulfilled the stringent criteria required for final evaluation. Tamoxifen was administered to them immediately prior to surgery and receptor status was studied on the surgical specimen. Estrogen receptor levels were significantly (p < 0.05) decreased after treatment, whereas progesterone receptors remained statistically unaltered, although they showed a tendency towards significant increase (p = 0.12). Following these results, short-term tamoxifen treatment seems inadequate for the induction of significant levels of progesterone receptors in mammary carcinoma.