Flow cytometry in primary breast carcinomas: prognostic impact of S-phase fraction according to different analysis patterns.

BACKGROUND

The aim of the present work was to study the prognostic impact of ploidy and S-phase fraction (SPF) assessed according to recently described methods. These methods of analysis combine different ploidy groups and separate euploid (good) prognostic groups from noneuploid (bad) prognostic groups. The definition of euploidy varied according to the author; some of them even included aneuploid peaks with few events. A comparison was also drawn to the average SPF and the diploid peak SPF observed in aneuploid histograms.

METHODS

From January 3, 1990 to January 7, 1999, 1,984 previously untreated, invasive breast carcinoma samples were snap-frozen and processed for FCM. The present study evaluated all nondiploid and nonmultiploid histograms, using different analysis patterns and the values of the average SPF and diploid SPF.

RESULTS

SPF is a salient prognostic factor even after multivariate analysis for DFS and MFS. Using several methods of analysis of ploidy and SPF shows that the classical method of analysis involving separation of ploidy according to diploidy versus aneuploidy and analysis of SPF restricted to the aneuploid peak in nondiploid and nonmultiploid histograms is as relevant as other recently proposed patterns of analysis, and that the average SPF or the diploid SPF of aneuploid tumors does not add significant prognostic information.

CONCLUSIONS

SPF is a valuable predictor of survival and can be confidently assessed in a simple way by restricting the analysis to the peak of interest (except for multiploid tumors).