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Prognostic Implication of N1b Classification in the Eighth Edition of the Tumor-Node-Metastasis Staging System of Differentiated Thyroid Cancer

2018; Mary Ann Liebert, Inc.; Volume: 28; Issue: 4 Linguagem: Inglês

10.1089/thy.2017.0473

1557-9077

Mijin Kim, Min Ji Jeon, Hye‐Seon Oh, Suyeon Park, Dong Eun Song, Tae‐Yon Sung, Tae Yong Kim, Ki‐Wook Chung, Won Bae Kim, Young Kee Shong, Yu‐Mi Lee, Won Gu Kim,

Medical and Biological Sciences

Regional lymph node metastases (LNM) have prognostic significance in differentiated thyroid cancer (DTC). However, there was no distinction between N1a and N1b in the final staging classification in the eighth edition of the tumor-node-metastasis (TNM) staging system. This study aimed to evaluate the prognostic implication of N1b classification for predicting disease-specific survival (DSS) in DTC patients with stage I/II disease.A total of 3089 patients with stage I/II DTC who underwent thyroid surgery between 1996 and 2005 were included. DSS was evaluated according to N classification and number of LNM. A modification of the TNM was assessed that classified N1b cases in patients aged ≥55 years as stage IIB and the remaining cases as stage IIA.The mean patient age was 45.6 years, and the median follow-up period was 10.0 years. In patients aged ≥55 years, patients with N1b had significantly poorer DSS compared to those with N0 (hazard ratio [HR] = 11.0; p < 0.001) and N1a (HR = 4.2; p = 0.013). The large-volume LNM group had significantly poorer DSS compared to the N0 (HR = 10.1; p < 0.001) and small-volume LNM (HR = 3.9; p = 0.019) groups. When patients were reclassified using the modified TNM staging system, DSS was significantly poorer in stage IIB patients than in stage IIA patients (HR = 2.9; p = 0.030).N1b classification has a significant prognostic implication in patients with stage I/II DTC, especially in older patients. Modified TNM staging employing N1b classification could be more useful for the prediction of DSS.