Pre-RAI Monocyte-to-Lymphocyte Ratio Predicts Early and Higher Recurrence Risk in Intermediate-Risk DTC, While PNI and NRI Show No Prognostic Value.

[OBJECTIVE] Differentiated thyroid carcinoma (DTC) has an excellent prognosis, but recurrence remains a clinical concern, especially in intermediate-risk patients. Current stratification systems focus primarily on tumor characteristics, overlooking the host's biological capacity to counteract tumor progression. To investigate this aspect, we assessed systemic inflammatory and nutritional status using hematological indices. The study aimed to evaluate the prognostic value of these markers in predicting recurrence risk in patients with intermediate-risk DTC.

[METHODS] We retrospectively analyzed consecutive patients with intermediate-risk DTC who met the following criteria: (1) were classified as intermediate risk according to ATA guidelines; (2) showed an excellent or indeterminate response 12 months after initial treatment; and (3) had at least three consecutive years of follow-up at our center after thyroidectomy. Nine hematological indices were calculated from blood samples collected on the day of RAI administration. Statistical analyses included ROC curve analysis, logistic regression, and Kaplan-Meier analysis.

[RESULTS] A total of 282 patients were included, with a median follow-up of 91 months. Among the indices tested, the monocyte-to-lymphocyte ratio (MLR) predicted recurrence better than the others. A cut-off of 0.188 yielded 82.9% sensitivity and 54.7% specificity (AUC: 0.70). In multivariate analysis, high MLR (OR  =  4.94, p  <  0.001), tumor size, vascular invasion, and lymph node metastases were independently associated with recurrence. Cox regression confirmed MLR as an independent predictor of shorter recurrence-free survival (HR  =  3.01, p <  0.001). Nutritional indices showed no prognostic value.

[CONCLUSIONS] Pre-RAI MLR may serve as a simple marker to refine recurrence risk stratification and personalize follow-up in intermediate-risk DTC.