Impact of gross extranodal extension into major neck structures on the prognosis of papillary thyroid carcinoma

Abstract

Objective

The AJCC-8 staging system for papillary thyroid carcinoma (PTC) excludes certain lymph node characteristics from stage determinants due to insufficient evidence of their prognostic impact. This study aimed to examine the influence of gross extranodal extension (N-Ex) on survival and recurrence by comparing outcomes of extrathyroidal extension (T-Ex) and N-Ex cases.

Methods

Patients with PTC who underwent initial surgical treatment and had T-Ex or N-Ex were selected. Their survival and recurrence rates were compared, focusing on age and stage classification. Patients younger than 55 years without distant metastasis (DM) are classified as Stage I, regardless of T-Ex or N-Ex. Patients aged 55 years or older without DM are classified as Stage II if they have N-Ex without T-Ex and Stage III or IVA if they have T-Ex. The prognoses of the T-Ex and N-Ex groups stratified by age were compared. Using the T-classification by organ involvement, older patients with N-Ex were subgrouped, and their prognoses were compared with those of the T-Ex group.

Results

The study included 183 T-Ex and 50 N-Ex without T-Ex cases. The disease-specific survival (DSS) and disease-free survival (DFS) of the two groups did not differ for the younger patients without distant metastases (Stage I in both groups). For the older patients without distant metastasis, the 10-year DSS was 80.6% and 48.5% for Stages III and IVA (with T4bAnyNM0; T-Ex group) and 74.7% for Stage II (with T1-3N-ExM0; N-Ex group). The 10-year DFS were 68.2%, 0%, and 64.5% for Stages III, IVA (T-Ex group), and II (N-Ex group), respectively. The DSS and DFS did not differ for Stages III and IVA (T-Ex group) and II (N-Ex group). The prognoses of the N-Ex subgroups and the older T-Ex group did not also differ.

Conclusions

The patients aged 55 years or older without DM had comparable prognoses, although cases with N-Ex without T-Ex were classified as Stage II, and those with T-Ex were classified as Stage III or IVA. The recurrence rates for the N-Ex and T-Ex stages were also comparable. These suggest that N-Ex is an important prognostic factor.