The new T3b category has clinical significance? SEER‐based study

Abstract

Objective As per the eighth edition of the American Joint Committee on Cancer (AJCC) staging system for differentiated thyroid carcinoma (DTC), minimal extrathyroidal extension (mETE) has been removed. Instead, gross ETE (gETE) invading only strap muscles has been designated as a new T3b category. Our objective was to investigate the impact of the T3b category on survival in order to establish its prognostic value in DTC. Design In this retrospective study, we included patients who had undergone thyroidectomy between 2004 and 2012. Data from the Surveillance, Epidemiology and End Results (SEER) database were examined. Methods We used the Kaplan‐Meier method and log‐rank test to analyse overall survival (OS) and cancer‐specific survival (CSS). The effect of potential predictors associated with survival were estimated using the Cox regression model. To minimize selection bias, propensity‐score matching (PSM) was performed. Results A total of 63 315 patients were included in our study. During the average follow‐up duration of nearly 78 months, significant differences were observed in cancer‐specific survival among patients with no ETE, mETE, gETE invading only strap muscles (T3b) and gETE invading perithyroidal structures other than strap muscles (T4) (P < .05). In univariable and multivariate analysis, both mETE and T3b exhibited significant poorer CSS compared with no ETE. After adjusting for patient features with PSM, it was confirmed that T3b was associated with worse CSS compared with no ETE and mETE. Conclusions Both mETE and gETE are independent factors for DTC, implying that the new T3b category is worthy of reference for medical workers. Furthermore, mETE was significantly associated with poorer outcome. Our conclusion may provide support for the modification of the TNM staging system in the future.

Minimal Extrathyroid Extension (mETE) as the Only Risk Factor in Patients with Papillary Thyroid Carcinoma (PC): Its Clinical Impact on Recurrence and Outcome during Long-Term Follow-Up

“…Other authors have reported that mETE may be associated with an increased risk of poor cancer-specific survival and overall survival, suggesting that it should be further investigated whether removing mETE from the last AJCC Staging System Manual is correct [25]. Furthermore, in other research, mETE was significantly linked to poor outcomes and the authors concluded that the TNM Staging System may need to be modified in the future due to this result [41]. It has been reported that even a small increase in thyroidal extension can lead to a significant increase in the risk of compromised survival.…”

Extrathyroidal extension or tumor size of primary lesion influences thyroid cancer outcomes

“…strap muscle) of the thyroid, it might be more challenging to completely resect the tumor foci invaded to the posterolateral organ, due to its close relation to critical laryngotracheal structures. Completeness of tumor resection and negative margins in surgery might be associated with better prognosis [26,27]. Papillary thyroid microcarcinoma was considered a good prognosis because of its nature of being indolent and easily being monitored by neck ultrasonography [28,29].…”

Prognostic Impact of Microscopic Extra-Thyroidal Extension (mETE) on Disease Free Survival in Patients with Papillary Thyroid Carcinoma (PTC)

“…Tran et al performed a retrospective analysis of DFS in 577 patients, in which microscopic ETE was associated with multiple other adverse prognostic features and reduced DFS [ 13 ]. Jingzhe Xiang et al found that mETE was significantly associated with poorer outcome on cancer-specific survival [ 14 ]. Parvathareddy et al analyzed a cohort of 1430 patients and suggested that m-ETE is an independent marker for poor recurrence-free-survival (RFS) [ 15 ].…”