Lymph Node Metastasis Ratio: Prognostic Significance in Papillary Thyroid Cancer

Abstract Prognostic stratification systems for papillary thyroid carcinoma (PTC) consider the presence and anatomical location of cervical lymphatic metastasis, not valuing its quantitative extent. Cervical metastasis lymph node ratio (MLNR) may be a quantitative tool with independent predictive value in PTC prognosis. This concept has been related with disease recurrence and patient outcomes. Retrospective observational study, including patients who underwent total thyroidectomy (TT) and lymphadenectomy, between 2002 and 2020, with PTC histopathological diagnosis. Two groups were considered: G1-with persistence/recurrence, and G2-without persistence/recurrence. MLNR (metastatic lymph nodes/total harvested nodes) and lateral compartment MLNR (LC-MLNR) (metastatic lymph nodes in the lateral compartment/total harvested nodes in the lateral compartment) were determined. A total of 60 individuals were included, with a mean age at the time of TT of 49.3 ± 2.3 years and a predominance of females [ n = 49 (81.7%)]. G1 ( n = 26 [43.3%]) showed a higher frequency of males (G1: 30.8% vs. G2: 8.8%; P = 0.029), extrathyroidal extension (G1: 76.9% vs. G2: 44.1%; P = 0.011), tumor size ( P = 0.032), extranodal extension (G1: 62.5% vs G2: 32%; P = 0.037), resection extent ≥ R1 (G1: 34.6% vs. G2: 8.8%; P = 0.034), and higher mean values of LNMR (G1:0.72 vs. G2: 0.18; P < 0.001) and LC-MLNR (G1: 0.68 vs. G2: 0.15; P = 0.003). After multivariate analysis, MLNR, tumor size and resection extent ≥ R1 remained as independent predictors of persistence and/or recurrence of PTC. MLRN seems to be proven to be independent predictor of PTC persistence and recurrence, potentially providing a complementary role to the available risk stratification systems. Consequently, it may optimize decision-making regarding targeted therapeutic strategies and surveillance.