Progesterone receptor immunohistochemical quantitation compared with cytosolic assay: Correlation with prognosis in breast cancer

Quantitation of estrogen and progesterone receptors (PR) represents the sta ndard of care in the treatment of patients with boast cancer. Historically this was performed by cytosolic assay; current methods utilize immunohistoc hemical staining, which may be quantitated visually or by image cytometry. Formalin-fixed paraffin embedded sections from 95 breast carcinomas were im munostained with an avidin-biotin complex technique, steam antigen retrieva l, and a monoclonal PR antibody (1/40 Biogenex). Nuclear immunostain was qu antitated visually as the percentage of immunopositive nuclei, scored as 0 to 4. By image cytometry, the percentage of positively staining nuclear are a (PPNA) was determined in 15 hpf using the CAS 200 Image Analyzer. Dextran -coated charcoal (DCC) ligand binding assay data were divided into negative (<10 fmol), low positive (10-50), or positive (>50). A statistically signi ficant correlation was found between stage (P = 0.0001), the presence of no dal metastases (P = 0.0001), cytosolic assay (P = 0.036), image cytometry ( P = 0.01), and disease-free survival. Only stage (P = 0.0001) and PR quanti tation per cytosolic assay (P = 0.0001) correlated with overall survival. T he method of choice for the assessment of PR hormone status in breast carci nomas is the DCC ligand binding assay. This method correlates with both sur vival and disease-free survival. Image cytometric quantitation of PR immuno histochemical staining correlates only with disease-free survival. The comm only used method of visual quantitation of PR immunostaining fails to relat e either to survival or disease-free survival.