Background: Cell kinetics and DNA ploidy have provided relevant information on the natural history of breast cancer. We assessed the prognostic role of proliferative activity and ploidy, alone and in association with tumor size, estrogen (ER) and progesterone (PgR) receptors.
Patients and methods: In a series of 340 women with resectable node-negative breast cancers given local-regional therapy alone until relapse, proliferative activity was determined as the 3H-thymidine labeling index (3H-dT LI) and flow-cytometric S-phase cell fraction (FCM-S), as quantified by using different modeling systems. DNA ploidy, ER and PgR content were determined on frozen samples by FCM and by the dextran-coated charcoal absorption technique, respectively.
Results: FCM-S estimates obtained by the different models were weakly associated with one another and to the corresponding 3H-dT LIs. Four-year relapse-free survival was significantly predicted by 3H-dT LI, ploidy and tumor size but not by FCM-S. Multiple regression analysis showed that 3H-dT LI, ploidy and tumor size retained their prognostic significance and that 3H-dT LI was the most significant indicator of relapse (p = 0.009).
Conclusions: The finding that 3H-dT LI and ploidy are weakly related and provide independent prognostic information could allow a more accurate identification of patients at different risk of relapse.