Implications of inconsistent measurement of ER status in non-invasive breast cancer: A study of 1,684 cases from the Sloane Project

The Sloane Project is an anonymized UK-wide audit of screen-detected atypical hyperplasia and in situ carcinoma of the breast. Full histopathology data have been provided by the local reporting pathologist on 1,684 of 2,615 cases entered to date. These include estrogen (ER), progesterone, and Her2 receptor status and the scoring/cut-off criteria for positivity used. We review the recorded data on receptor status of cases of ductal carcinoma in situ (DCIS) entered into the Sloane Project and the cut-off criteria for negative/positive status-determination for those cases. ER status was recorded on the Sloane Project pathology datasheets for 763 cases, 79% were positive and 21% negative. For hormone receptors, the distribution of use of the three scoring systems: Allred scoring, histoscore, and a simple percentage score was 62%, 21%, and 17%, respectively. Cut-off criteria were provided for 78% of the ER positive cases and 48% of ER negative cases. There was a wide range of cut-off values applied, with Allred scores of < 2-5, percentages of < 1-70%, and histoscores of 30-50. Reporting practice was commonly inconsistent within individual laboratories. Thirty-nine percent of ER positive patients were referred for consideration of endocrine therapy. Eight percent of patients were entered into clinical trials. There is a pressing need to standardize reporting of receptor status in DCIS and to give clear guidance on both scoring methodologies and recommended cut-off points. There are significant implications for the interpretation of clinical trials data in this area.