Standardization and quality control in the evaluation of proliferation parameters in T1T2, N0N1, M0 breast cancer: multicentric retrospective study II. DNA-ploidy and S-phase fraction

Ar part of a clinical research project, proliferative parameters were studi ed in primary breast cancer: standardization and technical validation of th ymidine kinase (TK), thymidylate synthase irs) and protein tyrosine kinase (PTK) are described A total of 633 frozen tumor specimens, available in fou r institutions, was analyzed in three flow cytometry laboratories for DNA c ontent and percentage of S-phase cells (%S) measurement 1) The standardizat ion step consisted in developing a common protocol for sample preparation; then, common cell suspensions were analyzed in order to perform an inter-la boratory control. Objective guidelines were elaborated to interprete DNA hi stograms in breast carcinoma. 2) DNA-aneuploidy was observed in 61% of case s of the retrospective series. Compared with DNA-aneuploid tumors, mean %S was significantly lower in case of DNA-diploidy (respectively: 6.4% and 2.2 %, p < 0.001). When compared between the four institutions, %S distribution s did not differ significantly. 3) %S is strongly correlated with TK TS and PTK and high percentages were also observed in high grade tumors or tumor without hormone receptors. These results show that a standardization in usi ng flow cytometers and DNA softwares allows multicenter studies.