After standard therapy, targeting other immune biomarkers in the primary tumor, such as CTLA-4 that is often detected in inflamed breast cancers, TIM3 and LAG3 that are expressed in early-stage HER2+ BC [83,84], or IDO and CD73 that are identified in TILs after treatment with anti-PDL-1 antibodies [85,86], could revert resistance to standard treatments and improve clinical response and OS [87]. Here, IDO1 is linked to breast cancer.