Abstract P4-08-02: A Comparison between AQUA Quantitative Fluorescent Immunohistochemistry and Conventional Immunohistochemistry for Hormone Receptors

Abstract

Abstract Background: We have previous data showing that quantitation of hormone receptors can be highly informative in determining risk of early relapse in ER positive early breast cancer treated with tamoxifen or exemestane. Both quantitative immunohistochemistry (QIHC) and flouresecent immunohistochemistry (F-IHC as measured by AQUA technology) are highly prognostic over a wide expression range. We have explored the results of both assays to determine if current assays provide maximum information using current approaches. Patients & Methods: Pathology blocks from 4598 TEAM patients were collected and tissue microarrays constructed. Quantitative AQUA and IHC analysis (using image quantitation) of ER and PgR was performed centrally (Edinburgh & HistoRx). Results from both assays were compared and their prognostic impact on DFS at 2.75 years examined. Results: Both AQUA and QIHC demonstrated linear relationships between intensity of staining for either ER or PgR and DFS at 2.75 years. For both PgR and ER AQUA provided significantly greater prognostic information that QIHC. However AQUA staining explained only 29% and 68% of the variability in ER and PgR QIHC results by logistic regression. Using both AQUA and QIHC data in a forward stepwise selection survival model demonstrated that AQUA and QIHC provided similar prognostic information over 70% and 50% of the range for ER and PgR respectively. High ER QIHC and low ER AQUA scores, and low PgR IHC and high PgR AQUA scores provided prognostic information unique to either platform. Conclusion: Both QIHC and AQUA analysis of HR expression provides significant and highly important information on DFS risk in early breast cancer. It appears that these two platforms provide overlapping prognostic information and that the range of ER and PgR expression which impacts patient outcome is wider than measured by either system alone. Further investigation of the clinical significance of this broader range of hormone receptor expression in treatment decisions is warranted. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P4-08-02.