Modification of the eight-edition tumor-node-metastasis staging system with N1b for papillary thyroid carcinoma: A multi-institutional cohort study

Publication date: November 2018

Source: Oral Oncology, Volume 86

Author(s): Mijin Kim, Hee Kyung Kim, Hye In Kim, Eun Heui Kim, Min Ji Jeon, Hyon-Seung Yi, Eun Sook Kim, Hosu Kim, Tae Hyuk Kim, Bo Hyun Kim, Tae Yong Kim, Ho-Cheol Kang, Won Bae Kim, Jae Hoon Chung, Young Kee Shong, Sun Wook Kim, Won Gu Kim

Abstract

Objectives

Based on the tumor-node-metastasis staging system, eighth edition (TNM-8), N1b is no longer used as a variable to determine final stage in papillary thyroid carcinoma (PTC). We aimed to evaluate the predictability of a simple modification of the TNM staging with N1b classification in a large multicenter thyroid cancer cohort.

Materials and methods

This study included 7717 patients with PTC who underwent thyroid surgery between 1996 and 2005 from six tertiary hospitals. We classified patients with stage II into stage IIA and IIB with modified-TNM: older patients with N1b disease were classified as stage IIB, while remaining patients were classified as stage IIA.

Results

The mean age was 46.2 years, and 24% were aged ≥55 years. In older patients, the 10-year disease-specific survival (DSS) rate of N1b disease (86.3%) was approximately 10% lower than that of N1a disease, and patients with N1b had significantly poorer DSS than those with N1a (HR = 3.3, p < 0.001). When the modified-TNM was applied, DSS curves between stage groups significantly differed (p < 0.001), and the relative risk of DSS in stage IIB patients was 2.3 times higher than in stage IIA patients (p < 0.001). The proportion of variation explained value of the modified-TNM was 4.9% and that of the TNM-8 was 4.7%.

Conclusion

This multicenter study reveals that the presence of lateral lymph node metastasis affects disease mortality in PTC, especially in older patients. The sub-classification of stage II in older patients improves DSS predictability. This simple modification of TNM-8 provides better prognostic information for patients with PTC.

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