Estradiol and progesterone receptors content and response to norethisterone treatment in advanced breast cancer.

Twenty-six patients with advanced breast cancer and progressive disease were treated by norethisterone. Estradiol and progesterone receptors were measured before starting treatment, and in three cases after 2 to 4.75 months of therapy. Partial remissions (greater than 50% decrease of all lesions) or objective improvements (decrease of 20-50%) were obtained in 7 patients, with a mean duration of 6.7 months. Stabilization of the lesions (no change or decrease of less than 20% in the size of the target lesion) was observed in 7 patients. No clear-cut correlation was found between clinical response and presence in biopsies of estradiol and progesterone receptors. However, absence of response occurred more frequently if tumors did not contain progesterone receptors.