Background: The aim of this study was to compare the concordance between immunohistochemical (IHC) and biochemical (RIA) methods for determining hormone receptor status in patients with endometrial carcinoma and to determine whether IHC expression of estrogen and progesterone receptors (ER and PR) has prognostic significance.
Methods: Paraffin blocks were obtained from patients diagnosed with endometrial carcinoma between 1987 and 1991. IHC analysis for ER and PR expression was performed and scored based on staining intensity and the percentage of tumor cells with nuclear staining. Biochemical assays were performed on frozen tissues. Concordance between the two methods was evaluated and hormone receptor status was correlated with tumor grade, stage, recurrence and survival.
Results: ER and PR expression, determined by IHC, correlated well with RIA levels (Spearmans correlation coefficient, P = 0.006 and 0.0005, respectively). Determination of ER and PR expression by both methods was correlated with tumor grade. Hazards ratios revealed that the absence of ER and PR expression, determined by both IHC and RIA, independently correlated with recurrence in early stage disease (P < 0.05).
Conclusions: Historically, receptors have been determined by RIA. In this study, IHC and RIA were equally suitable for determination of ER and PR. This is significant clinically as IHC has several advantages over RIA, including easier processing, lower cost, greater speed, and applicability to fixed tissue samples. In addition, ER negative status was predictive of the recurrence of Stage I tumors independent of tumor grade. ER status may aid the clinician in planning treatment when adjuvant treatment is controversial.
Copyright 1999 American Cancer Society.