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Neutrophil-to-lymphocyte ratio (NLR) is a calculated blood-based
inflammatory biomarker obtained by dividing the absolute neutrophil count by
the absolute lymphocyte count. It reflects the balance between systemic
inflammation, represented partly by neutrophils, and lymphocyte-mediated immune
activity.
In cancer, an elevated NLR is frequently associated with greater inflammatory
burden, impaired antitumour immunity, more advanced disease, poorer treatment
response, and reduced progression-free or overall survival. A decreased NLR is
therefore generally considered the favourable direction, although its meaning
depends on cancer type, disease stage, treatment, and the timing of measurement.
NLR is a nonspecific biomarker and may be altered by infection, corticosteroids,
chemotherapy, granulocyte colony-stimulating factors, bone-marrow suppression,
smoking, stress, and other inflammatory or medical conditions. There is no
single universal cutoff value; thresholds commonly vary between approximately
3 and 5 across studies.
Calculation: absolute neutrophil count divided by absolute
lymphocyte count.
Generally favourable cancer direction: decreased NLR.
NLR should be classified as a hematologic biomarker or inflammatory index rather
than as a direct molecular target.
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