Purpose
Breast cancer subtypes (BCS) determined from IHC staining have been correlated with molecular subtypes and associated with prognosis/outcomes, but there are limited data correlating these BCS and axillary node involvement. This study was conducted to assess whether BCS predicted for nodal metastasis or was associated with other clinical-pathologic features at presentation.
Methods
Stage I/II patients who underwent breast-conserving surgery and axillary surgical assessment with available tissue blocks underwent a institutional pathological review and construction of a tissue microarray(TMA). The slides were stained for ER/PR/HER2-neu for classification into BCS. Nodal involvement and other clinical-pathologic features were analyzed to assess associations between BCS and patient/tumor characteristics. Outcomes were calculated a function of BCS.
Results
The study cohort consisted of 453 patients(LA 48.6%, LB 16.1%, HER2 11.0%, TN 24.2%), of which 22%(n=113) were node+. There were no significant associations with BCS and pN stage, node positivity, or absolute number of nodes involved (all p>0.05). However, there were significant associations with subtype and age at presentation (< 0.001), method of detection (p=0.049), tumor histology (p<0.001), race (p=0.041), and tumor size (pT stage, p<0.001) by univariate and multivariate analysis. As expected, 10-year outcomes differed by BCS, with TN & HER2/neu subtypes having the worse overall(p=0.03), disease-free(p=0.03) and distant metastasis-free survival(p< 0.01).
Conclusions
Our findings suggest that there is a significant association between BCS and age, T stage, histology, method of detection and race, but no associations to predict nodal involvement. If additionally validated, these findings suggest that BCS should not strongly influence regional management considerations.