Preoperative Inflammatory Ratios Poorly Discriminate Malignant From Benign Parotid Tumours

OBJECTIVE: To determine whether preoperative blood inflammatory ratios discriminate malignant from benign parotid tumours. METHODS: This retrospective single-centre study included 204 patients undergoing parotidectomy (45 malignant, 159 benign); inflammatory-index analyses included 45 malignant and 157 benign cases. The neutrophil-to-lymphocyte and monocyte-to-lymphocyte ratios were the two primary indices. Group differences were tested non-parametrically with multiplicity control, discrimination by receiver operating characteristic analysis and association by multivariable logistic regression. RESULTS: Median neutrophil-to-lymphocyte and monocyte-to-lymphocyte ratios were higher in malignant tumours (2.00 vs. 1.81 and 0.203 vs. 0.166), but effect sizes were small. Areas under the curve were 0.608 (95% confidence interval 0.518-0.701) and 0.631 (0.520-0.735), respectively. At the sample-derived neutrophil-to-lymphocyte threshold, sensitivity was 86.7% and specificity 35.7%. Additional inflammatory indices, histological subgroup analyses and sensitivity analyses did not materially improve discrimination. CONCLUSIONS: Although the two primary ratios were higher in malignant tumours, their distributions overlapped substantially and discrimination was poor. These findings do not support their use as stand-alone markers for preoperative malignancy risk stratification.