Association of lymph nodes positive rate with the risk of recurrence in patients with stage T1 papillary thyroid cancer

The incidence of lymph node metastasis in papillary thyroid carcinoma (PTC) is common and a significant risk factor for local recurrence; however, its impact on recurrence patterns among low-risk patients remains uncertain. We aimed to elucidate the effect of metastatic lymph node on recurrence type. The medical records of 1209 patients with stage T1 PTC who underwent unilateral thyroidectomy with ipsilateral central lymph node dissection were retrospectively analyzed. The study first identified risk factors for different types of recurrence and then categorized patients as high or low risk based on their lymph node positive ratio (LNPR). The diagnostic accuracy of LNPR in predicting recurrence was compared using receiver operating characteristic (ROC) curve analysis, while differences in recurrence-free survival were assessed using the Kaplan-Meier method. During follow-up, a total of 502(41.5%) patients had central lymph node metastasis and 52 (4.3%) patients experiencing recurrence. Notably, LNPR was significantly higher in relapsed patients compared to non-relapsed patients, with mean values of 0.45 and 0.23, respectively (P<0.001). The recurrence rate of residual thyroid did not differ significantly across different T stages (P=0.679), N stages (P=0.415), or LNPR risk groups (P=0.175). However, the recurrence rate of lymph nodes showed a significant correlation with LNPR (P<0.001). The area under the ROC curves for LNPR risk stratification at 5 and 10 years were approximately 0.691 and 0.634, respectively, both of which outperformed N-stage. The findings underscore the significance of LNPR's reliability as a prognostic indicator for local lymph node recurrence in patients diagnosed with T1 stage PTC.