Luminal Breast Cancer: Risk of Recurrence and Tumor-Associated Immune Suppression

Abstract

Hormone-receptor positive (HR+) breast cancer (BC) (including the luminal A and the luminal B subtypes) is the most common type of tumor in women diagnosed with early-stage BC (EBC). It represents a highly heterogeneous subgroup that is characterized by different risks of relapse. The aim of this review is to discuss the possible role played by the immune response in predicting this risk, along with the most common clinical and pathological factors and molecular tools that have been developed and are already in use. As opposed to what has previously been observed in the most aggressive human epidermal growth factor receptor 2 (HER2)-positive and triple-negative breast cancer (TNBC) subtypes, a high proportion of tumor-infiltrating lymphocytes (TILs)-reflecting a spontaneous and pre-existing immune response to the tumor-has been linked to a worse prognosis in HR+ EBC. This work provides some immune biological rationale explaining these findings and provides the basics to understand the principal clinical trials that are testing immunotherapy in HR+ (luminal) BC.

Fig. 1

The role of tumor microenvironment in hormone receptor-positive breast cancer. The tumor microenvironment of luminal breast cancer includes a variety of non-immune and immune cells producing many factors that can drive a chronic inflammatory, differently balanced situation: either a pro- and an anti-tumor or pro-angiogenic tumor microenvironment. TAM-1 tumor-associated macrophages type 1, TAM-2 tumor-associated macrophages type 2, FGF2 fibroblast growth factor 2, Fas-L Fas ligand, Fas Fas receptor