Risk stratification for lateral involvement in papillary thyroid carcinoma patients with central lymph node metastasis

Purpose To effectively predict lateral neck lymph nodes (LLN) metastasis in papillary thyroid carcinoma (PTC) patients with central lymph nodes (CLN) invasion, and devise targeted treatment strategies. Methods Four hundred and thirty-four PTC patients with CLN metastasis from two medical centers were retrospectively analyzed. A new statistical model was established for predicting LLN involvement in these patients to guide lymph nodes management strategies. Results Patients with more than five positive CLN metastasis appeared to have extremely high risk (83.0%) of LLN involvement. For patients with five or less positive CLN invasion, multivariate logistic analyses were applied. Independent risk factors for LLN involvement were determined to be: age over 40, maximum tumor diameter of no less than 1.0 cm, existence of thyroid capsular invasion, and tumor with ipsilateral nodular goiter (iNG). These factors were used to construct a predictive nomogram. The accuracy and validity of our newly built model were verified by C-index 0.761 (95% CI, 0.707-0.815) in development cohort and 0.759 (95% CI, 0.745-0.773) in validation cohort and calibration curve. The patients were stratified into three groups based on their nomogram risk scores. Possible LLN involvement rates for low-risk, moderate-risk, and relatively high-risk subgroups were 8.9%, 22.8%, and 48.2%, respectively. Conclusions Our newly established model can effectively predict possible LLN metastasis in PTC patients, and a new strategy selection flow chart was created for patients with positive CLN invasion. For patients in high-risk group, prophylactic LLN dissection is recommended, if not, adjuvant radioactive iodine or a closer follow-up scheme should at least be conducted. For those in low-risk group, surgical intervention is unnecessary and regular follow-up is recommended.