Background: This study was designed to evaluate the prognostic importance of c-erbB2 overexpression in a standardized cohort of patients with axillary lymph node positive breast cancer.
Methods: Paraffin embedded primary breast cancers from 354 patients with axillary lymph node positive breast cancer, treated on a North Central Cancer Treatment Group adjuvant protocol, were studied immunohistochemically. c-erbB2 staining was classified as negative, weak (1+), moderate (2+), or strong (3+) and was assessed for effectiveness as a predictor of outcome in univariate and Cox model multivariate analyses.
Results: Twenty percent of specimens exhibited moderate or strong c-erbB2 staining. The median disease free survival period of the strong staining group was 2.9 years, compared with 7.1 years for all other patients (P = 0.01). The median overall survival for the strong staining group was 5 years, compared with 12 years for all other patients (P = 0.03). A definite correlation was noted between degree of nodal involvement and the likelihood of strong c-erbB2 staining (P = 0.001). There was also a significant correlation between c-erbB2 staining and higher nuclear grade and estrogen receptor negativity. In a multivariate analysis, c-erbB2 staining was not a significant predictor of either disease free survival or overall survival.
Conclusion: According to this analysis, the strong correlation between c-erbB2 expression and degree of nodal involvement, higher grade disease, and estrogen receptor negativity suggests expression of this protooncogene product in a biologically more aggressive form of breast cancer. In a multivariate analysis, c-erbB2 expression was not an independent prognostic factor. Thus, c-erbB2 assessment did not appear to add significantly to the information provided by currently available standard disease parameters.