The prognostic value of hormone receptor detection by enzyme immunoassay and immunohistochemistry: a prospective study in patients with early breast cancer

The main reason to determine estrogen (ER) and progesterone receptors (PR) in breast cancer is their predictive value for the response to endocrine therapy. In addition, ER and PR are often used as prognostic indicators. Enzyme immunoassay (EIA) and immunocytochemical assay (ICA) are two methods for determining ER and PR. These two methods have not been compared with each other in relation to clinical endpoints. In the present study we prospectively evaluated the prognostic value of ER and PR as determined by ICA and EIA in 223 and 207 patients, respectively, with early breast cancer. ER was positive in approximately 77% of patients, while PR was positive in approximately 65% of patients. The proportion of potential agreement beyond chance between EIA and ICA was 0.58 and 0.65 for ER and PR, respectively. The median follow-up was 86 months. Both ER and PR appeared to be weak prognostic factors. There were no differences in prognostic value according to the time point of analysis or cutoff value chosen, nor were there any differences in the prognostic value of hormone receptors detected by ICA or EIA. Both methods appear to be equivalent in terms of qualification and prognostic value.