[Flow cytometry detected S-phase fraction and ploidy as prognostic parameters in primary, node-negative breast...

100 specimens of patients with primary node-negative breast cancer were examined by flow cytometry. 64 tumours were shown to be diploid and 36 tumours were aneuploid. The median was the cut-off level for tumours with low S-phase (< or = 10.9%) and high S-phase values (> 10.9%). Aneuploid tumours were associated with high S-phase fraction. The average length of follow-up was 42 months. In univariate analysis for disease-free survival, diploid tumours were shown to have a slightly better prognosis than aneuploid tumours (p = 0.07). This trend could not be shown in multivariate analysis. The S-phase fraction proved to be an independent prognostic factor. Patients, whose tumours had S-phase fractions < or = 10.9%, had significantly longer disease-free survival in univariate (long-rank-test: p = 0.021), as well as in multivariate analysis according to the Cox regression model (p = 0.033). Since, as already stated, the S-phase fraction is an independent prognostic factor for node-negative breast cancer, further adjuvant therapy studies should take this factor into consideration.