Peripheral Blood Mononuclear Cell Populations Correlate with Outcome in Patients with Metastatic Breast Cancer

Cells. 2022 May 13;11(10):1639. doi: 10.3390/cells11101639.


Local tumor-associated immune cells hold prognostic and predictive value in various forms of malignancy. The role of systemic, circulating leukocytes is, however, not well-characterized. In this prospective and explorative study, we aim to delineate the clinical relevance of a broad panel of circulating immune cells in 32 patients with newly diagnosed metastatic breast cancer (MBC) before the start of systemic treatment. Freshly isolated peripheral blood mononuclear cells (PBMCs) were analyzed by flow cytometry and evaluated for potential associations to clinicopathological variables and patient outcome. We show that the levels of specific circulating leukocyte populations are associated with clinical parameters such as hormone receptor status, histological subtype, number of circulating tumor cells (CTCs) and metastatic burden. Importantly, high levels of CD8+ cytotoxic T lymphocytes (CTLs) are significantly linked to improved overall survival (OS). In patients with estrogen receptor (ER)-positive primary tumors, high levels of circulating CTLs and non-classical (CD14+CD16++) monocytes were associated with improved OS, whereas in patients with ER-negative tumors low levels of circulating natural killer (NK) cells potentially associate with improved OS. We propose that the levels of specific circulating immune cell populations, such as CD8+ CTLs, may be used to predict clinical outcomes in MBC patients. Thus, larger studies are warranted to validate these findings.

Keywords: lymphocytes; metastatic breast cancer; myeloid cells; peripheral blood; prognosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antineoplastic Agents*
  • Breast Neoplasms* / pathology
  • Female
  • Humans
  • Leukocytes, Mononuclear / pathology
  • Monocytes / pathology
  • Neoplastic Cells, Circulating* / pathology
  • Prospective Studies


  • Antineoplastic Agents

Grants and funding

This work was generously supported by Governmental Funding of Clinical Research within the National Health Services (A.L.F.; A.-M.L., L.R. and K.L.), Vetenskapsrådet (L.R. and K.L.), Cancerfonden (L.R. and K.L.), the Swedish Society for Medical Research (SSMF; C.B.), the Gyllenstiernska Krapperup Foundation (K.L. and C.B.), the Gunnar Nilsson Cancer Foundation (C.B.), the Fru Berta Kamprad foundation (A.-M.L.), the Medical Faculty at Lund University (C.B.) and Allmänna Sjukhuset i Malmö Stiftelse för bekämpande av cancer (K.L. and C.B.).