Pre-ablation derived neutrophil-to-lymphocyte ratio is associated with time to complete disappearance after thermal ablation of benign thyroid nodules: a retrospective cohort study

Background Complete disappearance after thermal ablation for benign thyroid nodules is a time-dependent process with substantial inter-individual variability. Whether baseline systemic inflammatory–immune status contributes to the kinetics of post-ablation absorption remains unclear. Objective To evaluate the association between pre-ablation derived neutrophil-to-lymphocyte ratio (dNLR) and time to complete disappearance (VRR = 100%) after ultrasound-guided thermal ablation of benign thyroid nodules. Materials and methods This single-center retrospective cohort analyzed time to ultrasound-defined VRR = 100% as a time-to-event endpoint. Associations were assessed using Cox regression (log2-transformed dNLR per doubling), with stratification by ablation modality when needed. Discrimination was evaluated using Harrell’s C-index, and incremental value was assessed by comparing a prespecified clinical–procedural base model with and without dNLR. Results Over 60 months, 95/187 (50.8%) achieved VRR = 100% (median 37 months). dNLR per doubling was associated with earlier VRR = 100% in univariable analysis (HR 2.44, 95% CI 1.63–3.65; P < 0.001) and remained independently associated in the modality-stratified multivariable model (HR 2.28, 95% CI 1.51–3.43; P < 0.001). The model including dNLR showed moderate discrimination (C-index 0.728, 95% CI 0.675–0.782) and adding dNLR modestly improved discrimination (ΔC-index ≈ 0.02; likelihood ratio test P < 0.001). Conclusions Higher pre-ablation dNLR was independently associated with earlier complete disappearance after thermal ablation and may provide complementary information for counseling and follow-up planning; however, its incremental discrimination was modest and external validation is needed.