Objective: In 90 patients with primary node-negative breast carcinomas we compared the prognostic impact of total S-phase fraction (SPF) and MIB1 proliferation rate (MIB1-PR) after a median follow-up of 34 months (9-72 months).
Methods: SPF was determined flow cytometrically and MIB1 (Ki-67) immunohistochemically in parallel-cut, paraffin-embedded tissue sections.
Results: SPF was significantly correlated to tumor size and steroid hormone receptor status, MIB1-PR to grading. In univariate analysis both SPF and MIB1-PR were significant prognostic factors for disease-free survival. In multivariate analysis however, S-phase fraction was the only significant prognostic factor when compared to MIB1-PR, tumor size, steroid hormone receptor status, menopausal status, grading, lymph vessel invasion, and tumor necrosis.
Conclusions: In our study SPF was of higher prognostic strength and may therefore be better suited for clinical application than MIB1-PR in node-negative breast cancer.