Progesterone receptor expression is a marker for early stage breast cancer: implications for progesterone receptor as a therapeutic tool and target.

We determined the association of estrogen receptor (ER) and progesterone receptor (PR) expression in invasive breast cancer with stage at diagnosis. Univariate analyses indicated that although ER and PR expression were inversely associated with grade (P<0.0001), only PR expression (P<0.01) was inversely associated with stage. Multivariate analyses, adjusted for covariates, including HER-2/neu expression, indicated that PR (odds ratio (OR), 0.88; confidence interval (CI), 0.77-0.99; P=0.03) and not ER expression (OR, 1.04; CI, 0.94-1.16; P=0.45) was inversely associated with stage. PR and not ER expression is a marker for early stage breast cancer.