Steroid receptors have been routinely determined on surgically resected primary breast cancers since the late 1970s.45 Receptor-containing tumors have a better short-term prognosis, although the magnitude of this difference is relatively small (8 to 10 percent difference in recurrence rate for node-negative patients at 5 years).17,46 Long-term relapse and survival rates between receptor-positive and receptor-negative tumor patients, however, tend to merge.17,44,47 Despite this, steroid receptor assays are often used as a marker of probable sensitivity to tamoxifen or other agents that bind the estrogen receptor.
Determination of steroid receptors on cyto-logic or surgical preparations of primary breast tumors is standard and almost universally performed. Such tests should also be obtained on presurgical breast cancer samples (cytology or core biopsy) if neoadjuvant chemo- or radiotherapy will be given. Receptor determination may also be performed on tumor metastases if the steroid receptor status was not determined on the primary tumor or if there is reason to suspect biologic cancer progression (the development of an estrogen receptor-negative phenotype).
Immunochemical assays for estrogen and progesterone receptors (ER, PgR) are most often used.17 Pathologists evaluate the receptor status of the invasive component only. Generally, immunopositivity of benign breast epithelium adjacent to the cancer is sought as an internal positive control for the assay. Many pathologists have developed their own definition of positivity, which is used in reporting. This may include evaluation of the percentage of cells staining as well as consideration of stain intensity. An effort should be made to have the local institutional scoring system defined and the methodology clearly stated in the assay report. Methods and scoring differences have been estimated to contribute to disagreements between laboratories in up to 30 percent of specimens. Data on ER from archival cases often used different methodologies for ER or PgR, and cut-off levels for positivity were generally determined by the local laboratory. Immunohistochemical methods now in use for ER and PgR can be applied to archival fixed-embedded tissue specimens that are decades old, should concern arise about old hormone receptor data.
The estrogen receptor is a good example of a marker that is both prognostic and predictive. Patients with tumors that are ER positive are more likely to have a better outcome independent of treatment. These same patients are also more likely to respond to tamoxifen therapy (a positive predictive factor).17 Adding to the complexity of the issue, recent data suggest that optimal ER assay cut points may be different to optimize either prognostic or predictive estima-tions.48 In summary, ER and PgR have both positive prognostic and predictive values associated with a more favorable patient outcome.
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