A substantial change in breast cancer (BC) biology arises after 50 years old regardless of patient (pt) menopausal status

Abstract

21002 Background: To explore the hypothesis that ageing alters BC biology, we correlated pt age at diagnosis with biopathological data collected retrospectively from 2723 BC pts treated at the Bordet Institute between 2000 and 2003. Pt's characteristics: Median pts’ age was 56 years old [25–96] and 36% of pt had nodal invasion. Seventy-eight and 63% of the BC were ER+ and PR+ respectively, 33% were grade 3, 24% overexpressed Ki67 (>25%) and 8% were Her2 FISH+. Results: Pts <40 years old had the highest Her2 FISH+ (12%) and hormone-independent (39%) BC rates. More than 50% of the BC were undifferentiated (grade 3) and highly proliferative (Ki67>25%). Moreover, lobular BC were almost absent in young pts (p<.0001); in agreement with the fact that lobular BC were less aggressive than ductal ones (less grade 3, Her2 FISH+ and ER- BC; p<.0001). Hence pts <40 years had a statistically higher rate of “Her2” and “basal-like” BC subtypes. On the contrary, pts >50 years had ‘better prognostic luminal-A” BC with 60% of hormone-dependent BC and a significant drastic decrease of Ki67 expression, tumor grading and Her2 FISH+ (all p=.002). No biological difference was observed between BC of pts >50 years. However, in this group we observed that high ER scores (7–8 vs 3–6) were statistically associated with Her2 FISH- and PR+ characteristics (all p<.0004). Interestingly, the 40–50 years old group which contains 16% of postmenopausal pts, appeared as a transition group according to its biology. Nevertheless, no statistically biological difference could be observed between the BC of pre- and postmenopausal pts. Additionally, when considering the postmenopausal pts from all ages, a clear difference was observed for the different parameters between tumors from pts <50 years compared to older ones (ER, p=.046; grade, p=.0007; Ki67, p=.0001), suggesting that age, and not the menopausal status, is responsible for changes in BC biology Conclusions: BC biology is greatly different in pts before and after the age of 50 but after 50 years old, all pts have BC with similar characteristics. Nevertheless, menopausal status can not account by itself to all these differences and pt ageing appears to have a great impact on BC biology (i.e. Her2 FISH+). No significant financial relationships to disclose.