Progress and pitfalls in the use of immunotherapy for patients with triple negative breast cancer

PD-1-blockade is approved for stage II/III TNBC and for first-line treatment of PD-L1-positive TNBC patients with metastatic disease and should be considered standard of care. However, question marks and difficulties remain; these include the identification of predictive biomarkers to select patients who benefit from the addition of PD1-blockade and the balance between efficacy and long-term toxicity for an individual patient. Numerous treatment combinations and new immunotherapeutic strategies beyond PD1 blockade are being evaluated, thus reflecting a promising evolution towards a more personalized approach, and extended clinical benefit in TNBC.Abbreviations:Triple-negative breast cancer (TNBC); breast cancers (BCs); estrogen receptor (ER); progesterone receptor (PgR); human epidermal growth factor-2 (HER-2); basal-like 1 (BL1), basal-like 2 (BL2); mesenchymal (MES); mesenchymal stem-like (MSL); immunomodulatory (IM); luminal androgen receptor (LAR); basal-like immunosuppressed (BLIS); basal-like immune-activated (BLIA); tumor-infiltrating lymphocytes (TILs); tumor mutational burden (TMB); immune cells (ICs); immunohistochemistry (IHC); overall response rate (ORR); overall survival (OS); progression-free survival (PFS); intention-to-treat (ITT); hazard ratio (HR); confidence interval (CI); Food and Drug Administration (FDA); European Medicines Agency (EMA); immune checkpoint inhibitors (ICI); Combined Positive Score (CPS); disease control rate (DCR); neoadjuvant chemotherapy (NACT); pathological complete response (pCR); event-free survival (EFS); disease-free survival (DFS); residual cancer burden (RCB); San Antonio Breast Cancer Symposium (SABCS); antibody-drug conjugates (ADCs); PARP inhibitors (PARPi); clinical benefit rate (CBR); Histone deacetylase inhibitors (HDACi); Dendritic cell (DC); talimogene laherparepvec (TVEC); granulocyte-macrophage colony-stimulating factor (GM-CSF); mismatch repair deficiency (dMMR).