The peripheral immune landscape of human breast cancer.

The clinical management of patients with breast cancer is largely dictated by tumor stage, disease subtype and (at least in some settings) specific molecular features thereof (e.g., BRCA1 mutations, PD-L1 positivity). However, not all patients with breast cancer respond to therapeutic approaches that a priori are precisely targeted to their disease. At least in part, this may reflect the fact that breast neoplasms are highly heterogeneous from a broad immunological perspective, even when they exhibit similar disease subtype and molecular features. Thus, integrating extra immunological parameters into current decision-making algorithms may considerably improve clinical management in this large patient population. In this context, circulating indicators of global immune fitness and ongoing anticancer immunity stand out as particularly promising tools for minimally invasive prognostic and/or predictive assessments. Here, we summarize and critically discuss the circulating immune landscape of human breast cancer, whenever possible comparing across disease subtypes, stages, and treatment outcomes.