S-PHASE FRACTION IDENTIFIES HIGH-RISK SUBGROUPS AMONG DNA-DIPLOID BREAST CANCERS

The prognostic value of DNA content measured by means of flow cytometr y was analyzed in formalin-fixed, paraffin-embedded samples from 231 b reast cancer patients treated between 1984 and 1988, with a mean follo w-up period of 55 months. We followed the guidelines of a Consensus Me eting held on this issue in Maine, USA, in 1992. DNA-diploid and -aneu ploid tumors were evaluated separately for the fraction of cells in S- phase (SPF) contained in them, this being divided into three groups (' high', 'intermediate', and 'low'), defined by the 25th and 75th centil e of the SPF-distribution corresponding to either DNA-diploid or DNA-a neuploid tumors. Unequivocally readable histograms were obtained from 174 samples (75.3%). A high SPF in diploid tumors was significantly as sociated with a higher recurrence rate (p = 0.015), a shorter disease- free survival (p = 0.014), advanced (IIIB) clinical stage (p = 0.034), and almost significantly with total survival (p = 0.055). In a multiv ariate Cox regression analysis, a high SPF in diploid tumors retained its independent prognostic power, being significantly associated with a shorter disease-free survival (p = 0.00049) and total survival (p = 0.0077). It also allowed to identify a subgroup with an ominous progno sis among patients less than or equal to 50 years of age with early st age tumors. Our results fully validate the recommendations of the 1992 Maine Consensus Meeting.