A Molecular Perspective of Clinical Benefit: Why Shouldn’t Luminal a Breast Cancer Patients be Considered in Pathological Complete Response Discussions

Breast cancer is a spectrum of many subtypes with distinct biological features that lead to differences in response patterns to various treatment modalities and clinical outcomes. Gene expression profiling has led to the molecular classification of breast cancer characterized by intrinsic subtypes: basal-like, HER2-positive, luminal-A, and luminal-B [1]. Up until recently, the subtypes were frequently treated as similar entities. However, there are obvious differences in subtype biological and prognostic characteristics. These differences are clearly evident in the neoadjuvant setting with pathological complete response (pCR) rates being the surrogate marker of efficacy to a therapeutic regime [2,3].