Abstract
Objectives: Since the eighth edition of the American Joint Committee on Cancer tumor-node-metastasis (AJCC/TNM) cancer staging system introduced some significant changes, we investigated whether patients with stage T1-2N1M1 differentiated thyroid cancer (DTC) should be placed in stage IVB, with the goal of providing suggestions for improved survival prediction.Materials and Methods: We divided 30,234 DTC patients aged ≥55 years enrolled from the Surveillance, Epidemiology, and End Results (SEER) database into different stage groups based on the new stage system but in a more thorough manner. Univariate and multivariate Cox regression analyses were conducted to explore the clinicopathological factors associated with cancer-specific survival. Survival of different stage groups was assessed by mortality rates per 1,000 person-years, Cox proportional hazards regression analyses, and Kaplan-Meier analyses with log-rank tests and the propensity score matching method.Results: Univariate and multivariate analyses demonstrated that age at diagnosis, T stage, lymph node metastasis, distant metastasis, histological types, extrathyroidal extension, and radiation therapy were associated with cancer-specific survival. Patients with stage T1-2N1M1 had a lower cancer-specific mortality rate per 1,000 person-years (28.081, 95% confidence interval [CI]: 12.616–62.505) and all-cause mortality rate per 1,000 person-years (70.203, 95% CI: 42.323–116.448) than those with low-level stages such as stage T4aN1M0, stage IVA, and stage T1-2N0M1. Cox proportional hazards regression analyses suggested that patients with stage T4bN1M0 belonging to stage IVA (hazard ratio: 2.529, 95% CI: 1.018–6.278, p = 0.046) had a significantly higher risk of cancer-specific mortality than those with stage T1-2N1M1. Kaplan-Meier analyses with log-rank tests suggested that the cancer-specific survival curve of patients with stage T1-2N1M1 had a more modest decline than that of stage T4bN1M0 (p = 0.0125), and the cancer-specific survival curve and all-cause survival curve of patients with stage T1-2N1M1 were not different from those of stage T3N1M0, stage T4aN0M0, stage T4aN1M0, stage T4bN0M0, and stage T1-2N0M1 (all, p > 0.05). The analysis yielded similar results after propensity score matching for other clinicopathological characteristics.Conclusion: Patients aged ≥55 years with stage T1-2N1M1 DTC according to the eighth edition AJCC/TNM cancer staging system should be downstaged and those with stage T4bN1M0 upstaged accordingly.
Highlights
Thyroid cancer is the most common malignant endocrine cancer, and its incidence has rapidly increased in the world in recent years [1, 2]
We explored the clinicopathological factors associated with cancer-specific mortality (CSM) using univariate and multivariate Cox regression analyses and compared the CSM and all-cause mortality (ACM) rates per 1,000 person-years of the same or adjacent AJCC/TNM-8 stage groups
Based on the results of the univariate Cox regression analyses, the CSM of Differentiated thyroid cancer (DTC) patients was associated with age at diagnosis, year at diagnosis, sex, race, T stage, lymph node metastasis (LNM), distant metastasis (DM), histological types, extrathyroidal extension (ETE), radiation therapy, and surgery
Summary
Thyroid cancer is the most common malignant endocrine cancer, and its incidence has rapidly increased in the world in recent years [1, 2]. There are a variety of cancer staging systems for DTC, all of which are aimed at discriminating among different prognostic groups. The 10-year cancer-specific survival (CSS) rate for stage I based on the eighth edition of the American Joint Committee on Cancer tumor-nodemetastasis (AJCC/TNM) cancer staging system is almost 99%. The eighth edition of AJCC/TNM cancer staging system (AJCC/TNM-8) was introduced in clinical practice on January 1, 2017. In this revision, the age cutoff value was revised from 45 to 55 years, and the descriptors of the T and N stages were changed from those contained in the seventh edition [7, 8]. Nearly 30% of DTC patients were downstaged following the introduction of the new edition [8]
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