Comparable long-term survival outcomes after lobectomy versus total thyroidectomy treatment of minimal extrathyroidal extension differentiated thyroid cancer patients.

[BACKGROUND] Differentiated thyroid cancer (DTC) patients (tumor size ≤4 cm) with minimal extrathyroidal extension (MEE), which was used to be classified as T3 disease, now are classified as T1/T2 disease according to the largest tumor size. However, few studies explored the survival difference between DTC patients with MEE who received lobectomy or total thyroidectomy treatment. We aimed to compare the long-term survival rate of DTC patients with MEE after total thyroidectomy and lobectomy by using the national cancer registration data.

[METHODS] We performed a retrospective cohort analysis to examine the long-term survival outcomes after lobectomy versus total thyroidectomy treatment of DTC patients with MEE using the univariate and multivariate survival analysis.

[RESULTS] Of 1,889 included DTC patients with MEE, 113 patients (6.0%) received lobectomy and 1,776 patients (94.0%) received total thyroidectomy. DTC patients with MEE who underwent lobectomy experienced a similar cancer-specific survival (CSS) rate compared with those who underwent total thyroidectomy (10-year CSS rate: 99.1% 98.8%, P=0.99). Considering deaths not related to thyroid cancer, the 10-year cumulative incidence of cancer-related death was 0.9% for DTC patients with MEE who underwent lobectomy and 1.2% for those who received total thyroidectomy (P=0.99). After adjusting for potential confounding factors, DTC patients with MEE who received lobectomy experienced a similar risk of death compared to those who underwent total thyroidectomy in both the multivariate Cox regression model [adjusted hazard ratio (HR), 1.99; 95% confidence interval (CI): 0.45-8.80; P=0.36] and the multivariate competing risk regression model [adjusted subdistribution hazard ratio (SHR), 1.99; 95% CI: 0.44-8.89; P=0.37].

[CONCLUSIONS] pT1/pT2 DTC patients with MEE who underwent lobectomy or total thyroidectomy have excellent comparable survival outcomes, which supports the increased use of lobectomy in the treatment of these patients.