Metronomic cyclophosphamide treatment in metastasized breast cancer patients: immunological effects and clinical outcome

Cancer Immunol Immunother. 2012 Mar;61(3):353-62. doi: 10.1007/s00262-011-1106-3. Epub 2011 Sep 14.


Severe immune suppression is frequent in late-stage tumor patients and promotes tumor immune evasion and subsequent tumor progression. Regulatory T cells (Treg) are major suppressors of anti-tumor immune responses. Therefore, targeting of Treg has become a key goal of anti-tumor therapy. Several preclinical and clinical observations suggest that Treg can be depleted by cyclophosphamide. Over a period of 3 months, we investigated the effect of metronomic low-dose cyclophosphamide on Treg numbers, suppressive capacity and proliferation on endogenous anti-tumor T-cell responses and on their correlation to clinical outcome in 12 patients with treatment-refractory metastasized breast cancer who received single-agent 50 mg cyclophosphamide p.o. daily. Cyclophosphamide treatment initially caused a significant reduction in circulating Treg by more than 40% (P = 0.002). However, Treg numbers completely recovered during the treatment due to increased proliferative activity and maintained their suppressive capacity. Treg depletion coincided with a strong increase in breast tumor-reactive T cells (P = 0.03) that remained at high levels during the whole period. Numbers of tumor-reactive T cells but not of Treg correlated with disease stabilization (P = 0.03) and overall survival (P = 0.027). We conclude that metronomic low-dose cyclophosphamide only transiently reduces Treg but induces stable tumor-specific T-cell responses, which correlate with improved clinical outcome in advanced-stage breast cancer patients.

Publication types

  • Clinical Trial

MeSH terms

  • Adult
  • Aged
  • Antineoplastic Agents, Alkylating / administration & dosage
  • Antineoplastic Agents, Alkylating / therapeutic use
  • Breast Neoplasms / drug therapy*
  • Breast Neoplasms / immunology
  • Breast Neoplasms / pathology
  • CD4-Positive T-Lymphocytes / drug effects
  • CD4-Positive T-Lymphocytes / immunology
  • CD4-Positive T-Lymphocytes / metabolism
  • CD8-Positive T-Lymphocytes / drug effects
  • CD8-Positive T-Lymphocytes / immunology
  • CD8-Positive T-Lymphocytes / metabolism
  • Cell Line, Tumor
  • Cyclophosphamide / administration & dosage
  • Cyclophosphamide / therapeutic use*
  • Dose-Response Relationship, Drug
  • Female
  • Humans
  • Interferon-gamma / immunology
  • Interferon-gamma / metabolism
  • Lymphocyte Count
  • Middle Aged
  • Neoplasm Metastasis
  • Survival Analysis
  • T-Lymphocytes, Cytotoxic / drug effects
  • T-Lymphocytes, Cytotoxic / immunology
  • T-Lymphocytes, Cytotoxic / metabolism
  • T-Lymphocytes, Regulatory / drug effects*
  • T-Lymphocytes, Regulatory / immunology
  • T-Lymphocytes, Regulatory / metabolism
  • Time Factors
  • Treatment Outcome
  • U937 Cells


  • Antineoplastic Agents, Alkylating
  • Interferon-gamma
  • Cyclophosphamide