Rethinking the 8th AJCC System: Is It Suitable for Patients Aged

Wei Long,Yueye Huang,Liang Guo,Man Li,Di Hu,Jianglong Huang,Wen Zeng,Zeming Liu,Yihui Huang,Chao Zhang,Wei Wei,Sichao Chen,Min Wang,Wei Zhou,Ling Zhou

doi:10.3389/fonc.2020.543055

Abstract

PurposeThe newest (8th) edition of the TNM staging system published in 2017. In this edition, some significant changes happened from the previous edition. As a result, down-staging appeared in nearly one third of DTC patients. However, we don’t know whether the new system predicts the survival of FVPTC patients accurately. Therefore, it is necessary to thoroughly evaluate the correlation between the new system and survival prediction in terms of FVPTC.MethodsWe enrolled 17,662 FVPTC patients from the Surveillance, Epidemiology, and End Results database. Factors associated with survival were identified by Cox regression analyses. The mortality rates per 1,000 person-years were calculated and compared. Cox proportional hazards regression quantified the risk of survival, and survival curves were produced by Kaplan-Meier analyses using log-rank tests.ResultsAge at diagnosis, race, T-stage at diagnosis, distant metastasis, radiation therapy, and surgery were independent factors associated with cancer-specific survival. Patients aged <55 years with stage T4N1M0 FVPTC had higher mortality rates per 1,000 person-years than patients in the same stage according to the 8th AJCC System. Cox proportional hazards regression reflected that patients aged <55 years with stage T1-3, any N, M0 or T4N0M0 disease (p=0.001) and patients aged ≥55 years with T1-2N0M0 disease (p=0.004) had signiﬁcantly lower risks of cancer-specific survival (CSS) than those aged <55 years with stage T4N1M0 disease. The CSS curve of patients aged <55 years with stage T4N1M0 disease showed a decline on comparison with others belonging to stage I (p<0.001); and the curve was even not different from patients in stage II and stage III (p>0.05).ConclusionPatients aged <55 years with stage T4N1M0 FVPTC had worse survival than patients in stage I; no difference was seen on comparison with stage II patients. We recommend this group of patients be upstaged in the 8th AJCC system.

Highlights

follicular variant of papillary thyroid carcinoma (FVPTC) is a major subtype of thyroid cancer, which is the most common endocrine malignancy [1]
We focused on whether each subgroup of different stages aligns with its newest classification and compared the survival in these subgroups
AJCC Staging Grouping (8th Edition) Stage at diagnosis I Stage at diagnosis II Stage at diagnosis III Stage at diagnosis IV

Summary

Introduction

FVPTC is a major subtype of thyroid cancer, which is the most common endocrine malignancy [1]. Some studies have shown that the incidence of thyroid cancer has substantially increased in the last few decades [2, 3]. The global thyroid cancer incidence rates have undergone a 3.8‐fold increase since the 1970s [3, 4]. 90% of malignant thyroid tumors involve differentiated thyroid cancer (DTC), and DTCs are classified as either papillary thyroid carcinoma (PTC) or follicular thyroid carcinoma based on the histologic pattern [5]. PTC, as the most frequent type of thyroid malignancy, has two main subtypes: pure papillary thyroid carcinoma and follicular variant of papillary thyroid carcinoma (FVPTC). FVPTC is composed of follicles lined by cells exhibiting nuclear features of PTC [6]

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