Metastatic lymph node ratio (MLNR) could become the method of choice to predict cancer-specific survival in patients with medullary thyroid carcinoma (MTC), according to an article recently published in Head & Neck.

“Metastatic lymph node ratio stratifies cancer-specific survival in patients with MTC better than the number of node metastases or [Tumor Node Metastasis/American Joint Committee on Cancer (TNM/AJCC)] N classification after removal of more than 10–20 nodes,” the authors wrote.

This retrospective study included 505 patients previously diagnosed with MTC. The researchers calculated the cancer-specific survival of all participants using 3 different methods: the MLNR, the number of lymph node metastases, and the TNM/AJCC. All curves were considerably different from each other.


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The MLNR system was the stratifying method that most accurately predicted survival among the participants compared to the other 2 systems. This technique classified patients according to ratio increments of 0.20 or less, 0.21 to 0.60, and greater than 0.60. The authors hypothesized that the success of this system could be due to its ability to represent the intensity of tumor metastasis to the lymph nodes.

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Moreover, avoiding a dichotomous classification may have translated into more precise results by indirectly lowering the MLNR, providing a better representation of the actual population of patients with MTC.

Although MLNR yields promising results, it also possesses some limitations. For example, to achieve a proper ratio, a minimum of 10 lymph nodes must be dissected, with 20 being an ideal sample. In most cases, increasing the number of analyzed lymph nodes also increases the MLNR.

“This difficulty may help explain why the TNM/AJCC classification for thyroid cancer, unlike TNM/AJCC classifications for other cancers, considers simply the location of node metastases in the central (pN1a) or lateral neck (pN1b), but not metastatic lymph node ratio or the number of node metastases,” the study authors explained.

Reference

Machens A, Lorenz K, Weber F, Dralle H. 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. Head Neck. Published online September 6, 2022. doi:10.1002/hed.27181