Nomograms to predict occult contralateral central lymph node metastases in unilateral papillary thyroid carcinoma with ipsilateral clinical lymph node metastasis

Background: No significant difference in disease-specific survival and recurrence-free survival exists between papillary thyroid cancer (PTC) patients with high-risk features subjected to lobectomy and thyroidectomy. However, it is unclear which type of patients with unilateral PTC combined with ipsilateral clinical involved lymph nodes (cN1) can receive a less aggressive treatment. Methods: We collected the medical records of 631 patients diagnosed with unilateral PTC and ipsilateral cN1. These patients initially underwent total thyroidectomy and bilateral central lymph node dissection (LND), with or without lateral LND. We conducted an analysis to investigate the associations between contralateral occult central lymph node metastasis (CLNM) and clinicopathologic factors. Results: The proportion of contralateral occult CLNM was 38.9 %. Age <= 45 years, tumor diameter >1 cm, obesity, and involvement of lymph node regions >= 2 were independent risk factors for contralateral occult CLNM. Multifocality and ipsilateral neck high-volume lymph node metastases were independent risk factors among the postoperative pathological factors. A predicting model was developed to quantify the risk of each factor, which revealed that patients without any of the risk factors mentioned above had a 20-30 % probability of contralateral occult CLNM, whereas the probability was greater than 60 % when all factors were present. Conclusion: Based on the predictive nomograms, we proposed a risk stratification scheme based on different nomogram scores. In the debate about prophylactic central LND among contralateral central lymph node in unilateral PTC with ipsilateral clinical LNM, our nomograms provide the balance to avoid overtreatment and undertreatment through personal risk assessment.