(HealthDay)—In an American Society of Clinical Oncology/College of American Pathologists updated guideline, published online Jan. 13 in the Archives of Pathology & Laboratory Medicine and the Journal of Clinical Oncology, recommendations are presented for estrogen and progesterone receptor (ER/PgR) testing in breast cancer.
Kimberly H. Allison, M.D., from the Stanford University School of Medicine in California, and colleagues convened a multidisciplinary international expert panel to update the clinical practice guideline recommendations for ER and PgR testing in breast cancer.
The expert panel continues to recommend validated immunohistochemistry for ER testing of invasive breast cancers as the standard for predicting benefit from endocrine therapy. Samples with 1 to 100 percent of tumor nuclei positive should be considered ER-positive. However, limited data are available on the benefit of endocrine therapy for cancers with 1 to 10 percent of cells staining ER-positive, now described in a new reporting category called ER-low positive. A sample with <1 or 0 percent of tumor cell nuclei immunoreactive should be considered ER-negative. To promote optimal performance, interpretation, and reporting of cases with an initial low to no ER staining result, additional strategies include establishing a laboratory specific standard operating procedure describing additional steps used to confirm/adjudicate results. PgR testing continues to be used primarily to help determine prognosis in ER-positive breast cancers. Testing ductal carcinoma in situ for ER is recommended while testing for PgR is considered optional.
“The critical point for clinicians is that they need to be aware of and able to discuss with patients the implications of ER-low positive test results,” a coauthor said in a statement.
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