Heterogeneous Prognoses for pT3 Papillary Thyroid Carcinomas and Impact of Delayed Risk Stratification.

Background: Papillary thyroid carcinomas (PTC) in the pT3 category constitute a heterogeneous group of tumors with a variable risk of recurrence. The objectives of this study were (i) to estimate disease-free survival (DFS) and identify prognostic factors associated with recurrence in a cohort of pT3 PTC, and (ii) to evaluate the concept of delayed risk stratification in a cohort of pT3 tumors.
Methods: A total of 560 patients with pT3 PTC, treated and followed at the authors' institution, were studied. They were divided into three groups: group 1, pT3 ≤10 mm; group 2, pT3 >10 mm with extrathyroidal invasion (ETI); and group 3, pT3 due to a tumor size >4 cm. DFS was estimated using the Kaplan-Meier method, and associated prognostic features were studied in univariate and multivariate Cox model-based analyses in each group. Then, DFS was studied for each group according to the six- to eight-month status (remission or not).
Results: DFS at 10 years was 75% for the entire cohort and was 89%, 67%, and 82% in groups 1, 2, and 3, respectively (p < 0.0001). Multivariate analysis identified three factors significantly associated with reduced DFS: lymph node (LN) involvement, male sex, and group 2 (>1 cm with ETI). A trend toward a worse prognosis in patients with pT3 N0/Nx PTC >10 mm with ETI was found in comparison with the other pT3 N0/Nx patients. When the six- to eight-month checkup was normal, the DFS at 10 years increased to 98%, 96%, and 91% in groups 1-3, respectively. Furthermore, in this case, initial LN involvement no longer seemed to affect the prognosis in those groups.
Conclusion: PTC ≤10 mm with ETI and large tumors >4 cm without ETI both have a low-recurrence risk when there are no adverse associated prognostic features such as LN involvement. LN involvement, especially in the lateral compartment (N1b), is a strong prognostic factor of recurrence in pT3 PTC. Delayed risk stratification can be applied in pT3 PTC patients. Those cured at the first checkup, including those with limited LN involvement, have excellent outcomes, which should prompt clinicians to adapt subsequent management accordingly.