PREDICTIVE VALUE OF ESTROGEN-RECEPTORS EVALUATED BY QUANTITATIVE IMMUNOHISTOCHEMICAL ANALYSIS IN BREAST-CANCER

To establish the reliability and biologic importance of quantitative i mmunohistochemical assays for estrogen receptors, more than 200 stage I and II breast cancers were studied. Immunohistochemical analysis was performed using antibody ER 1D5 (AMAC Westbrook, ME) in an automatic stainer (Tech Mate, Biotek, Santa Barbara, CA). Nuclear stain was quan titated by image analysis (SAMBA 1000; IPI, Chantilly VA). Statistical analyses were performed using Kaplan-Meier product limit estimator fo r quantitated values and Cox regression for risk for death and disease progression. Estrogen receptor values obtained using the dextran-coat ed charcoal method were available for comparison. Quantitated immunohi stochemical values, expressed as mean optical density of stained nucle i, could discriminate groups of patients that had as much as 3 times h igher risk for death and 2.5 times higher risk for disease relapse (P =.006 and P =.018, respectively). Patients could be divided into three risk groups, based on their overall and disease-free survival, that w ere statistically significant (P =.018). The same analysis was perform ed using biochemically assayed estrogen receptors values showing that at a cutoff value of 20 fmol/mg, estrogen status predicted overall sur vival, albeit with lesser probability values (P =.032). These results show that quantitative immunohistochemistry of estrogen receptors prov ides results that have better predictive value than the biochemically procured ones. This approach not only obviates many pitfalls of the me thods requiring tissue homogenates but also allows simultaneous correl ation with histopathologic tumor features and expression of other rele vant markers.