A comparison of the 7th and 8th editions of the AJCC staging system in terms of predicting recurrence and survival in patients with papillary thyroid carcinoma

Abstract

ObjectivesThe recently published 8th edition of the American Joint Committee on Cancer (AJCC) tumour-node-metastasis (TNM) staging system was significantly updated following the thyroid cancer-related guidelines to provide better predictability of survival but not focus on recurrence. Therefore, we compared the predictive values of the 7th and 8th editions of the AJCC staging systems for recurrence-free survival (RFS) and overall survival (OS) after thyroidectomy for papillary thyroid carcinoma (PTC). MethodsThis retrospective study included 2930 patients who underwent thyroidectomy and neck dissection for previously untreated PTC between 2006 and 2014. TNM stage was defined according to 7th and 8th editions. Univariate and multivariate Cox proportional hazard regression analyses were used to identify associations between variables and RFS or OS. Multivariate models for the AJCC TNM stages were adjusted for clinical and pathological variables. ResultsA significant number of patients classified as T3 with overall TNM stages II–IV in the AJCC 7th edition were down-staged in the 8th edition. Unadjusted T classification and overall TNM staging in both the 7th and 8th editions were significantly associated with RFS and OS rates (P < 0.001). After adjustment for clinicopathological factors, the overall TNM stage according to the AJCC 8th edition, but not the 7th edition, remained significantly associated with RFS and OS (P < 0.05), with better predictability of recurrence and survival, in patients with PTC. ConclusionsThe 8th edition AJCC staging system down-staged a large proportion of PTC patients, resulting in better predictability of recurrence and survival compared to the previous staging system. Condensed abstractThis study compared the abilities of the 7th and 8th edition AJCC staging systems to predict recurrence and overall survival in 2930 patients with papillary thyroid carcinoma. The updated guidelines down-staged a large proportion of patients, resulting in better prediction of recurrence and survival than the previous staging system.