Prognostic Impact of Primary Tumor Size in Papillary Thyroid Carcinoma without Lymph Node Metastasis.

Abstract

Background: We aimed to investigate the prognostic significance of primary tumor size in patients with pT1-T3a N0 M0 papillary thyroid carcinoma (PTC), minimizing the impact of confounding factors.

Methods: A multicenter retrospective study included 5,759 patients with PTC. Those with lymph node metastasis, gross extrathyroidal extension (ETE), and aggressive variants were excluded. Patients were categorized by primary tumor size (≤1, 1.1-2, 2.1-4, and >4 cm) and subdivided based on the presence of microscopic ETE (mETE).

Results: The median age was 48.0 years, and 87.5% were female. The median primary tumor size was 0.7 cm, with mETE identified in 43.7%. The median follow-up was 8.0 years, with an overall recurrent/persistent disease rate of 2.8%. Multivariate analysis identified male sex, larger tumor size, and the presence of mETE as significant prognostic risk factors. The 10-year recurrent/persistent disease rates for tumors ≤1, 1.1-2, 2.1-4, and >4 cm were 2.5%, 4.7%, 11.1%, and 6.0%, respectively. The 2.1-4 cm group had a significantly higher hazard ratio (HR), with the >4 cm group had the highest HR than the ≤1 cm group. Patients with mETE had a higher recurrent/persistent disease rate (4.5%) than those without, with rates by tumor size being 2.6%, 5.6%, 16.7%, and 8.2%.

Conclusion: Larger tumor size and the presence of mETE significantly increased the risk of recurrent/persistent disease in PTC. Patients with pT2-T3a N0 M0 PTC (>2 cm) had a recurrent/persistent disease risk exceeding 5%, warranting vigilant management.