Papillary Thyroid Cancer: What is necessary from cN1b to pN1b?

Abstract Objective To compare the differences among patients with papillary thyroid cancer (PTC) whose rapid intraoperative biopsy results indicating positive (pN1b) or negative lymph node metastasis while their preoperative ultrasound result indicating lymph node metastasis in the right lateral region (cN1b) without exception so as to explore whether there is a high risk of long-term metastasis in patients with papillary thyroid cancer (PTC) who have no lymph node metastasis (pN1a or pN0) as indicated by rapid intraoperative biopsy results at present. Meanwhile, to establish predictive models to help clinicians distinguish and screen high-risk populations and adopt different follow-up strategies. Method A retrospective analysis was conducted on clinical data of patients who underwent right neck side area biopsy or dissection (cN1b) at the Affiliated Drum Tower Hospital, Medical School of Nanjing University from January 2017 to August 2022 to establish a predictive model.The model will then be validated on patients who undergo right neck lateral area biopsy or clearance from September 2022 to August 2023. Data including demographic characteristics, pathological results, and laboratory examinations were collected. The predictive model was established and evaluated by SPSS 26.0 and R 4.3.1. Result This study includes a total of 316 patients diagnosed with papillary thyroid carcinoma and with preoperative ultrasound indicating lymph node metastasis in the neck lateral compartment (cN1b), who were treated at the Affiliated Drum Tower Hospital, Medical School of Nanjing University from January 2017 to August 2023. The training set included 264 patients, and the validation set included 52 patients.The area under the ROC curve for the prediction model is 0.83, with a diagnostic optimal threshold of 0.595. At this threshold, the model achieves a sensitivity of 81.6% and a specificity of 75.2%. Similar results were obtained when utilizing the model on the validation set. Age ≤ 55 years, male, tumor maximum diameter > 1.35cm, metastasis to non-lymph node posterior to right recurrent laryngeal nerve (NLN-prRLN), metastasis to lymph node posterior to right recurrent laryngeal nerve (LN-prRLN), tetraiodothyronine (TT4) ≤ 89nmol/L, and thyroglobulin (TG) > 37.5µg/L are independent risk factors for right lateral lymph node metastasis. Conclusion There are distinct disparities in demographics, pathological result, and laboratory examinations that can differentiate between high-risk and low-risk populations for lymph node metastasis in the right lateral region. These differences can be effectively identified by developing predictive models. The resulting prediction model based on these results demonstrates a high level of accuracy and can assist clinical doctors to make appropriate clinical decisions to pick out individuals who need preventive lymph node dissection in the right neck side area or to increase postoperative follow-up frequency, in order to reduce the recurrence of the malignant tumor and improve long-term prognosis.