S-phase fraction as an independent prognostic factor in invasive breast carcinoma - a study of long-term follow-up

Purpose: To evaluate the significance of the S-phase fraction (SPF) and DNA ploidy, determined by DNA flow cytometry, as prognostic markers in invasive breast cancer. Methods: Between October 1986 and June 1999,143 breast carcinoma patients, treated by surgery, were analyzed. Flow cytometry was performed for the identification of the SPF and DNA ploidy, with immunohistochemistry performed on paraffin embedded material for the hormone receptor. Two SPF classes were defined on the basis of the median value (10) by using a log rank test (high SPF > 10, low SPF < 10). The correlation between SPF and the clinicopathological factors (tumor size, lymph node status, histological grade and steroid receptor status) and between the SPF and 5 yr disease-free survival (DFS) were investigated. Results: DNA ploidy was not associated with tumor size, lymph node status, histological grade, overall survival and DFS. In a univariate analysis, high SPF values were associated with shorter 5 yr DFS in individual groups. In the node negative group, the 5 yr DFS of the low SPF group was higher than that of the high SPF group, but in the node positive group, the SPF values showed statistical significance with the 5 yr DFS. In a multivariate analysis, the SPF was independently associated with the 5 yr DFS in the node negative group. Conclusion: These results suggested the SPF is an independent prognostic factor in lymph node negative, estrogen receptor positive and progesterone receptor negative breast cancers.