An increase in tumor-infiltrating lymphocytes after treatment is significantly associated with a poor response to neoadjuvant endocrine therapy for estrogen receptor-positive/HER2-negative breast cancers.

An increase in TILs after NET was significantly associated with a poor response to NET. Given that FOXP3 + T-cell counts increased, and neutrophil counts did not decrease in patients with increased TILs after NET, the induction of an immunosuppressive microenvironment was speculated to play a role in the inferior efficacy. These data might partially indicate the involvement of the immune response in the efficacy of endocrine therapy.