Analysis of Neutrophil/Lymphocyte Ratio as a Potential Biomarker Stratified by Breast Cancer Histologic Subtype

<b>Background/Objectives</b>: Breast cancer is the most common cancer in women. The neutrophil/lymphocyte ratio (NLR) is an emerging biomarker from peripheral blood that has been associated with breast cancer prognosis in some studies; however, some studies fail to demonstrate an association. We stratified breast cancer patients into invasive lobular carcinoma (ILC) and invasive ductal carcinoma (IDC) cohorts to evaluate if any meaningful association could be found in either cohort between NLR and mortality. Additionally, no prior studies have examined the relationship between NLR and background parenchymal enhancement (BPE) on breast MRI, an imaging feature linked to increased breast cancer risk and a potential imaging prognostic biomarker, so we examined the relationship between BPE and NLR in the two cohorts. <b>Methods</b>: This retrospective study included 794 breast cancer patients who had either IDC or ILC. Radiologists' MRI reports and their BI-RADS categorization of BPE (1 = minimal, 2 = mild, 3 = moderate, 4 = marked) were extracted and recorded. The NLR was calculated from blood counts obtained prior to treatment. Tumor characteristics were also recorded. <b>Results</b>: For patients with ILC, NLR was found to be associated with mortality. Additionally, patients with ILC and a high BPE had a significantly higher mean NLR compared to all other groups, including low BPE groups and all IDC groups. <b>Conclusions</b>: There is potential value in using NLR, a readily available blood biomarker, in models predicting prognosis in ILC patients.