Clinical Outcomes and Prognostic Biomarkers Exploration Between HER2 Low and HER2 Zero eBC Patients

From 1997 until 2021, 5,378 eligible patients with operable breast cancer were treated, within the context of 3 randomized and 4 observational clinical studies with dds-CT including taxanes and anthracyclines. Adjuvant hormonal and radiation treatment were administered, as indicated. IHC and FiSH data from patients enrolled in the above randomized phase III trials conducted by the Hellenic Cooperative Oncology Group (HeCOG) will be retrospectively reviewed. All patients have signed a study-specific written informed consent before randomization, consenting for the trial and permitting the use of their biological material for future research purposes. All studies were conducted in accordance with the Declaration of Helsinki. Tumor material is examined mainly on tissue microarrays (TMA). Although, there is a HER2 assessment from local pathology laboratories, all tumors are re-evaluated centrally for ER, PgR and HER2 in the laboratory of Molecular Oncology according to ASCO/CAP guidelines. Tumors are subtyped with immunohistochemistry (IHC4) for ER, PgR, HER2 and Ki67. FISH is performed for the assessment of HER2 gene status. IHC for EGFR and CK5 is used for the classification of basal-like tumors; the expression of CD8 on TILs is also evaluated. Moreover, we investigate the mutational profile of Greek women with breast cancer, via the application of DNA Next Generation Sequencing (NGS) technologies, relative also to patient outcome. Patient demographic, clinicopathological and treatment data are available in all cases.