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Medline ® Abstract for Reference 67

of 'Hormone receptors in breast cancer: Clinical utility and guideline recommendations to improve test accuracy'

Interobserver concordance in implementing the 2010 ASCO/CAP recommendations for reporting ER in breast carcinomas: a demonstration of the difficulties of consistently reporting low levels of ER expression by manual quantification.
Reisenbichler ES, Lester SC, Richardson AL, Dillon DA, Ly A, Brock JE
Am J Clin Pathol. 2013;140(4):487.
OBJECTIVES: Endocrine therapy reduces recurrence risk by 30% to 50% in estrogen receptor (ER)-positive breast cancer. The ER-positive threshold recommended by the American Society of Clinical Oncology/College of American Pathologists is 1% based on studies using the ER-6F11 antibody. ER-SP1 antibody has a higher sensitivity and is more widely used.
METHODS: We report interobserver concordance manually measuring ER in 264 breast cancers using ER-SP1 and 1D5 and 2 scoring methods (H-score and Allred score).
RESULTS: With both antibodies, 3% to 4% of cases have a low level of ER expression (1%-10%), more than previously reported (<1%). We find a high level of paired observer concordance with both antibodies and scoring methods (κ= 0.892-0.943) with no significant difference with method of scoring. Despite excellent concordance, positive/negative discordance was almost 5% among 3 observers using either antibody, an underappreciated clinically significant rate.
CONCLUSIONS: Discordance overwhelmingly reflected differing opinions recording the proportion of tumor cells positive with low levels of expression (<10% staining; 12/13 cases).
Dept of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, MCN C-3321, 1161 21st Ave S, Nashville, TN 37232;Emily.s.reisenbichler@vanderbilt.edu.