HER-2 expression and cell proliferation: Prognostic markers in patients with node-negative breast cancer

Purpose: We analyzed the clinical relevance of HER-2 expression, widely investigated in breast cancer but with contradictory results, in the largest case series of node-negative breast cancer patients investigated to date. Patients and Methods: The pure prognostic value of HER-2 expression was investigated in 529 patients treated with locoregional therapy alone until early relapse. Proliferative activity was evaluated as [³H]thymidine labeling index and HER-2 expression by immunohistochemistry. All biologic determinations were conducted within the context of an intra- and interlaboratory National Quality Control Program. Results: HER-2 expression was not related to relapse-free survival in the overall series but was a significant discriminant of prognosis in the subgroup of patients with rapidly proliferating tumors. Six-year rate of relapse was 40% for patients with highly (≥30%) positive tumors and 26% for those with weakly HER-2-expressing tumors (P = .039). Conclusion: HER-2 expression in association with proliferative activity identifies a subgroup of node-negative breast cancer patients with the worst prognosis, who are candidates for specific intensive adjuvant therapy.