Superiority of metastatic lymph node ratio over number of node metastases and TNM / AJCC N classification in predicting cancer‐specific survival in medullary thyroid cancer

Background In medullary thyroid cancer (MTC), it is unclear which nodal classification system, metastatic lymph node ratio (MLNR), number of node metastases, or TNM/AJCC N classification, predicts cancer-specific survival best. Methods Kaplan–Maier analysis of cancer-specific survival after operation at a tertiary center. Results Included were 505 MTC patients. The spread of the survival curves was greatest after stratification by MLNR (in 0.20 increments), followed by number of node metastases (in 10-node and 20-node increments) and TNM/AJCC classification (N0, N1a, N1b). After collapsing overlapping survival curves, all adjacent curves (MLNRs ≤0.20 vs. 0.21–0.60 vs. >0.60; 0 vs. 1–20 vs. >20 node metastases; and TNM/AJCC N classification N0/N1a vs. N1b) significantly differed between each other. Conclusions In MTC, MLNR, reflecting intensity of lymphatic spread, predicts cancer-specific survival better than number of node metastases or TNM/AJCC N classification. The applicability of these findings to patients with limited neck dissection requires more research.