Recurrence Rate and Survival in 260 Patients With Oncocytic Thyroid Cancer According to Response to Initial Treatment...

BACKGROUND Oncocytic thyroid carcinoma (OTC) is a rare disease. There is little information about risk factors for recurrence. The aim of our retrospective, single-institution study was to investigate the recurrence rate in OTC patients with and without an excellent response after initial treatment according to the 2025 American Thyroid Association guidelines response criteria based on type of initial intervention. MATERIAL AND METHODS Altogether, 260 patients with OTC (57 men, 203 women; mean age 60.35 years; range 16-90 years) treated from 1972 to 2024 were included. Initially, regional and distal metastases were diagnosed in 15 (6%) and 25 (10%) patients, respectively. Cox's multivariate regression model was used to identify the risk factors for recurrence. RESULTS The follow-up period ranged from 0.1 to 45.2 (median 7.9) years. Recurrence was diagnosed in 39 (17%) of the 235 patients without disease after initial treatment. Locoregional, distant, and combined locoregional and distant recurrence was diagnosed in 18, 14, and 7 patients, respectively. Among 154 patients with an excellent response, recurrence occurred in 6.5%, and among the 81 patients without an excellent response, it occurred in 36% (P<0.001). Independent risk factors for recurrence were: sex (males, hazard ratio (HR)=2.5, 95% CI 1.3-4.8; P=0.009), age (≥55 years, HR=2.7, 95% CI 1.2-5.8; P=0.012), pT stage (pT3 or pT4, HR=1.4, 95% CI 1.0-1.9; P=0.023), and residual tumor after surgery (R1 or R2 residual tumor, HR=1.2, 95% CI 1.07-1.3; P=0.001). The 5-year disease-free survival rate for the entire cohort was 88%, while the 10-year and 20-year disease-free survival rates were 79%, and 74%, respectively. CONCLUSIONS Recurrence rate in patients with and without an excellent response was 6.5% and 35%, respectively. Recurrence was more common in men, older patients, those with regional metastases, and those with residual tumor after surgery.