11111 Background: Gene expression profiling of breast cancers has identified molecular subtypes (Lum A and B, basal, HER2) which impact upon the risk of both local and distant recurrence. There is interest in the impact of molecular subtype on outcome in T1a,bN0M0 tumors, a group thought to have good prognosis and to be amenable to breast conservation. The purpose of this study was to determine if presenting features of T1a,b tumors differ among molecular subtypes. Methods: Subtypes were classified using IHC as Lum A (ER±PR pos, HER2 neg); Lum B: (ER±PR pos, HER2 pos); HER2: (ER+PR neg, HER2 pos); or Basal: ER, PR, and HER2 neg. Data was obtained from a registered database which included patients treated in our institution between 1/98 and 6/07. Of 7906 eligible patients, 6016 were classifiable into molecular subtypes and 1974 tumors (32.8%) measured 10 mm or less. The Chi square test and ANOVA were used for statistical analysis. Results: Data are shown in Table 1 . Patients overexpressing HER2 were significantly younger, had more nodal involvement, multicentric/multifocal (Multi) disease, extensive intraductal component (EIC), and lymphovascular invasion (LVI) (all p<0.0001). On multivariate analysis the HER2 subtype had an odds ratio of 2.5 for Multi versus Lum A/B, but HER 2 was not predictive of nodal status. Conclusions: Even in small breast cancers, presenting features vary with molecular subtype. Unlike Multi, the higher incidence of positive nodes in HER2 patients is explained by traditional prognostic features such as grade, age, and size rather than subtype, suggesting that evaluation of traditional prognostic factors remains valuable in the molecular era. [Table: see text] No significant financial relationships to disclose.
Surgery for Good Prognosis Breast Cancers