Prognostic value of lymph node ratio in metastatic papillary thyroid carcinoma

Objective: Cervical metastases in papillary thyroid carcinoma are associated with increased recurrence. However, their effect on survival remains controversial. This study evaluated literature on the prognostic value of lymph node ratio for loco-regional recurrence and survival in metastatic papillary thyroid carcinoma. Methods: The PubMed database was systematically searched using the terms 'papillary thyroid carcinoma' and 'lymph node ratio'. Articles addressing the association between lymph node ratio and loco-regional recurrence or survival were identified. Results: Nine retrospective studies were included, comprising 12 400 post-thyroidectomy and neck dissection papillary thyroid carcinoma patients (median age, 48.6 years; 76 per cent females). Lymph node ratio was associated with worse recurrence-free survival in 60 and 75 per cent of studies investigating the effect of central compartment metastases and both central and lateral compartment metastases on recurrence-free survival, respectively. One large population-based study showed an association between lymph node ratio and disease-specific mortality in N-1 nodal disease, but failed to maintain the same association when N-1b patients were excluded. Conclusion: Regional lymph node ratio is an independent predictor for loco-regional recurrence in pathologically staged N-1 patients with papillary thyroid carcinoma. Patients with a high lymph node ratio should be closely followed up.