Progesterone receptors as a prognostic factor in Stage II breast cancer.

The presence of estrogen receptors in breast cancers is now accepted as a predictor of extended disease-free survival, but the relative value of progesterone receptors for this purpose has not been established. We have examined both receptors along with other risk factors in 189 patients receiving adjuvant therapy for Stage II breast cancer. The presence of either estrogen receptors or progesterone receptors was positively correlated with disease-free survival when analyzed separately, whether or not the adjuvant regimen included an endocrine component. However, when estrogen receptors and progesterone receptors were analyzed together in multivariate models, the presence of progesterone receptors was more significant than that of estrogen receptors for predicting time to recurrence, regardless of what other variables were included in the model. These data suggest that determination of the progesterone-receptor concentration is of equal or greater value than determination of the estrogen-receptor concentration for predicting the disease-free survival of patients with breast cancer. Future trials should include measurement of progesterone receptors.