Purpose: A study was undertaken to define the prognostic value of the expression of the c-erbB-2 oncoprotein in a series of breast cancer patients when compared by multivariate analysis with expression of the epidermal growth factor receptor (EGFR), DNA ploidy, and conventional clinicopathologic features.
Patients and methods: Prognostic indicators were analyzed in 165 primary breast cancers. The c-erbB-2 oncoprotein was recognized by the polyclonal antibody 21N using an immunocytochemical method. Expression of the EGFR was stated immunocytochemically using the monoclonal antibody EGFR1. DNA ploidy was assessed in paraffin-embedded sections using a standard flow-cytometric method.
Results: Overall, 27% of carcinomas had membrane 21N-staining and were classified as c-erbB-2-positive. Overexpression of the c-erbB-2 oncoprotein was poorly associated with EGFR expression and the conventional pathologic features, and it was weakly associated with DNA ploidy and nodal status. Univariate analysis showed that c-erbB-2 expression, nodal status, DNA ploidy, and EGFR provided significant prognostic information concerning 4-year relapse-free survival (RFS) with the odds ratios (ORs) of not relapsing of 2.94, 2.83, 2.34, and 2.20, respectively. Regarding overall survival (OS) at 4 years, only nodal status and DNA ploidy had prognostic significance, with the ORs of not dying of 2.68 and 2.80, respectively. Applying multivariate analysis to RFS, 21N when adjusted for nodal status, EGFR, and DNA ploidy (full model) failed to retain prognostic value (P = .202), whereas nodal status was the most significant indicator of relapse (P = .027) followed by DNA ploidy (P = .056) and EGFR (P = .093).
Conclusions: This study suggests that overexpression of the c-erbB-2 oncoprotein appears to be an important indicator of relapse in stage I-II breast cancer when singly evaluated. Multivariate analysis shows that the determination both of nodal status and DNA ploidy improves our ability to identify subsets of patients with different prognoses, and allows for a better selection of patients for systemic adjuvant treatments.