The impact of minimal extrathyroidal extension on survival outcomes in patients with pT1 and pT2 differentiated thyroid cancer.

Abstract

Minimal extrathyroidal extension, detected only through histologic examination, remains a topic of ongoing debate regarding the prognostic importance of differentiated thyroid cancer. Patients with pT1 and pT2 differentiated thyroid cancer from 2004 to 2015 were collected from the Surveillance, Epidemiology, and End Results database on 3 March 2025. The median follow-up period was 129 months for both patients with pT1 and pT2. Multivariate analyses were conducted to evaluate differences in lymph node involvement or distant metastasis, as well as survival outcomes between patients with pT1 and pT2 differentiated thyroid cancer with and without minimal extrathyroidal extension. Patients with PT1 and pT2 with minimal extrathyroidal extension had a significantly greater risk of lymph node involvement or distant metastasis compared with those without in the multivariate logistic analysis (pT1: adjusted odds ratio, 4.15; 95% confidence interval, 3.83-4.48; P < .001; pT2: adjusted odds ratio, 4.69; 95% confidence interval, 4.23-5.20; P < .001). Patients with pT1 with minimal extrathyroidal extension experienced a similar hazard risk of cancer-specific death to those without in the multivariate Cox analysis (adjusted hazard ratio, 1.41; 95% confidence interval, 0.91-2.21; P = .127) and the multivariate competing risk model (adjusted subdistribution hazard ratio, 1.44; 95% confidence interval, 0.92-2.27; P = .111) whereas patients with pT2 with minimal extrathyroidal extension experienced a significantly greater risk of cancer-specific death than those without in the multivariate Cox analysis (adjusted hazard ratio, 2.48, 95% confidence interval, 1.77-3.49; P < .001) and the multivariate competing risk model (adjusted subdistribution hazard ratio, 2.50; 95% confidence interval, 1.72-3.63; P < .001). Minimal extrathyroidal extension was an independent risk factor of lymph node involvement or distant metastasis in patients with pT1 and pT2. Minimal extrathyroidal extension did not significantly affect survival in patients with pT1, but it was an independent prognostic factor for survival in patients with pT2. Therefore, more aggressive treatment strategies are warranted for patients with differentiated thyroid cancer with minimal extrathyroidal extension, particularly those classified as pT2.