Tamoxifen and endometrial carcinoma: alterations in estrogen and progesterone receptors in untreated patients and combination hormonal therapy in advanced neoplasia.

Estrogen receptors and progesterone receptors were measured in tumors from patients with previously untreated endometrial carcinoma before and after a 5-day course of tamoxifen citrate. On initial biopsy, 13 of 25 tumors (52%) were progesterone receptor-positive, whereas 21 of 25 tumors (84%) were progesterone receptor-positive after tamoxifen. Grades 1 and 2 tumors were more likely to demonstrate this increased incidence of measurable progesterone receptors. Considering these results, and the work of others who have shown that progesterone receptor-positive metastatic endometrial cancer is more responsive to progestin therapy than are progesterone receptor-negative tumors, we instituted a phase II clinical trial of tamoxifen plus progestin for patients with recurrent endometrial carcinoma. Thus far, however, the 33% total response rate achieved with the combination therapy has not been superior to standard progestin therapy.