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.

Keywords

• thyroid cancer, papillary
• tumor size
• microscopic extrathyroidal extension
• lymph node metastasis