Should local therapy for invasive breast cancer be customized on the basis of subtype?

Microarray analyses have identified intrinsic breast cancer subtypes with distinct gene expression profiles. These subtypes can be approximated by immunohistochemical analysis of markers routinely available in pathology reports, in particular hormone receptors (HR) and HER2. These approximated subtypes can be used to stratify patients with regard to long-term recurrence-free and breast cancer-specific survival, and local-regional recurrence (LRR)-free survival. Patients who are HR-/HER2- have the highest risk of LRR; however, there are no data supporting more aggressive local-regional treatment with surgery or radiation to reduce that risk for this group. It is possible that local-regional therapy could be limited for patients with more favorable subtypes (HR+/HER2-); however, more data are needed to support this strategy.