NCCN Task Force Report: Estrogen Receptor and Progesterone Receptor Testing in Breast Cancer by Immunohistochemistry

The NCCN Task Force on Estrogen Receptor and Progesterone Receptor Testing in Breast Cancer by Immunohistochemistry was convened to critically evaluate the extent to which the presence of the estrogen receptor (ER) and progesterone receptor (PgR) biomarkers in breast cancer serve as prognostic and predictive factors in the adjuvant and metastatic settings, and the ability of immunohistochemical (IHC) detection of ER and PgR to provide an accurate assessment of the expression of these biomarkers in breast cancer tumor tissue. The task force is a multidisciplinary panel of 13 experts in breast cancer who are affiliated with NCCN member institutions and represent the disciplines of pathology, medical oncology, radiation oncology, surgical oncology, and biostatistics. The main overall conclusions of the task force are ER is a strong predictor of response to endocrine therapy; ER status of all samples of invasive breast cancer or ductal carcinoma in situ (DCIS) should be evaluated by IHC; IHC measurements of PgR, although not as important clinically as ER, can provide useful information and should also be performed on all samples of invasive breast cancer or DCIS; IHC is the main testing strategy for evaluating ER and PgR in breast cancer and priority should be given to improve the quality of IHC testing methodologies; all laboratories performing IHC assays of ER and PgR should undertake formal validation studies to show both technical and clinical validation of the assay in use; and all laboratories performing IHC assays of hormone receptors in breast cancer should follow additional quality control and assurance measures as outlined in the upcoming guidelines from the American Society of Clinical Oncology and College of American Pathologists.