Preoperative prediction of central lymph node metastasis in cN0T1/T2 papillary thyroid carcinoma: A nomogram based on clinical and ultrasound characteristics.

Background: Preoperative status of central lymph nodes is a key determinant of the initial surgical extent for papillary thyroid carcinoma (PTC). We aimed to develop and validate a nomogram based on preoperative clinical characteristics and ultrasound features to predict central lymph node status in patients with clinically lymph node-negative (cN0) T1/T2 PTC.

Methods: This retrospective study included 729 patients with cN0T1/T2 PTC who were treated between January 2015 and March 2020. Based on the ratio of 6:4, 431 patients who underwent surgeries relatively earlier comprised the training set to develop the nomogram, while the other 298 who underwent surgeries relatively later comprised validation set to validate the performance of nomogram. Least absolute shrinkage and selection operator (LASSO) regression and multivariate logistic regression were used to identify predictors of central lymph node metastasis (CLNM). These variables were used to construct a nomogram for predicting the risk of CLNM. The predictive performance, discriminative ability, calibration, and clinical utility of the nomogram model were evaluated in both sets.

Results: A total of 313 (42.9%) PTC patients were identified with CLNM. On multivariate logistic regression analyses, malegender, younger age, larger maximum diameter, multifocality, capsular invasion, infiltrative margins, intra-nodular vascularity, and aspect ratio >1 were independent risk factors for CLNM. Nomogram integrating these 8 factors showed excellent discrimination in the training [area under the curve (AUC): 0.788] and validation (AUC: 0.829) sets, and obtained well-fitted calibration curves. The cut-off value of this nomogram was 0.410 (∼245 points). Decision curve analysis confirmed the clinical utility of the nomogram.

Conclusion: The CLNM-predicting nomogram can facilitate stratification of cN0T1/T2 PTC patients. Prophylactic central neck lymph node dissection can be considered for those with high nomogram scores.