Breast cancer (BC) is the most common female malignancy within the spectrum of human cancer. One promising way to reduce the mortality and morbidity of BC is to explore novel diagnostic markers for early diagnosis and prognostication. The neutrophil lymphocyte ratio (NLR) is a good reflection of inflammation, which plays an important role in tumor progression and metastasis. However, the association between NLR and BC prognosis remains unclear. The aim of this meta-analysis is to explore the prognostic value of NLR in BC. Among the screened references in the database, 12 eligible studies were identified in this study. Patients with a higher NLR had a shorter disease-free survival (hazard ratio =1.46, 95% confidence interval: 1.12-1.90, P=0.044) and overall survival (hazard ratio =2.03, 95% confidence interval: 1.41-2.93, P<0.001). In the subgroup analysis of NLR and disease-free survival, the studies from Eastern countries had a positive result with perfect homogeneity (I (2)=0); however, this homogeneity has not been achieved in studies from Western countries. In the subgroup analysis of the NLR and overall survival, the results of the univariate and multivariate analyses were completely different, with different heterogeneity. In the luminal A and luminal B subtypes, we found that there was no association between the NLR and overall survival in the BC patients. Positive results were obtained in the analyses of the human epidermal growth factor receptor 2 (HER2)-positive and triple-negative BC subtypes. In conclusion, this meta-analysis suggests that NLR is a good prognostic marker for BC, and patients with a higher NLR have poorer prognoses. Future studies should perform more detailed investigations to decrease heterogeneity and determine the appropriate cut-off values for different races.
Keywords: disease-free survival; inflammatory factor; lymphocytopenia; lymphocytosis; neutrophilic leukocytosis; neutrophilicgranulocytopenia; overall survival; prognosis.