S-phase fraction, lymph node status and disease staging as the main prognostic factors to differentiate between young and older patients with invasive breast carcinoma

The influence of age on the outcome of patients with invasive breast carcinoma (IBC) has not yet been fully established. The present study investigated two subgroups of patients either side of the age spectrum, and evaluated cytometric, histopathological and molecular characteristics. The series involved 219 patients with IBC that had long-term follow-up, which were divided into two subgroups: Young (≤45 years; n=103) and old patients (≥75 years; n=116). Immunohistochemical evaluation of hormonal receptors, Ki67 index and HER2 status (plus HER2 silver hybridization in equivocal cases) were used as the basis for surrogate molecular subtyping. Ploidy and S-phase fraction (SPF) were analysed by DNA flow cytometry. Differences between the subgroups' characteristics were assessed by the two proportion Z test. Kaplan-Meier estimation and log-rank test were applied for survival analyses. The median age in the subgroups were 40 years (range, 19-45 years) in the young group and 78 years (range, 75-91 years) in the older subgroup. Young patients exhibited higher lymph node involvement, more advanced disease staging, higher SPF tumour proliferative activity, and a trend of lower incidence of Luminal A and higher incidence of Luminal B tumours. The median SPF value was significantly higher in young patients [7.1% (range, 1.5-23.7%) vs. 4.5% (range, 0.7-26.4%)], whereas the ploidy pattern showed no significant difference. In the whole series, as within IBC of no special type, young patients had a higher rate of recurrence (46.6 vs. 22.4%; P