[A single-center study on the oncological outcomes of active surveillance of thyroid nodules measuring≤1 cm with highly suspicious ultrasound features].

To investigate the oncological outcomes of active surveillance (AS) in patients showing thyroid nodules measuring≤1 cm with highly suspicious ultrasound features. A prospective single-center cohort study. A total of 534 patients with highly suspicious thyroid nodules (2015 American Thyroid Association Nodule Sonographic Patterns and Risk of Malignancy: High Suspicion) were enrolled in this study, the patients received AS at Peking Union Medical College Hospital between January 2017 and November 2022 to assess oncological outcomes (disease progression, recurrence/metastasis rate, etc). The patients were followed up every 6 months for physical examination and neck ultrasound examination. And the value of tumor volume changes in evaluating tumor enlargement was explored too. There were 413 females and 121 males in this cohort, with a mean age of (42.6±11.8) years. During a median follow-up period of 45.6 months (ranged from 3.5 to 176.0 months), disease progression occurred in 26 patients (4.9%) with highly suspicious thyroid nodules, characterized by a minimum 3-mm increase in tumor diameter in 19 patients (3.6%) and lymph node metastases in 7 patients (1.3%). Forty-seven (8.8%) patients opted for delayed surgery, with 29 patients due to a change in preference. There was no significant differences in pathologic and follow-up outcomes between patients with disease progression and preference change. Patients aged≤40 years had a higher cumulative incidence of 5-year disease progression than those aged>40 years (4.9% vs 1.9%, =0.060). No patients experienced distant metastases or deaths. Among the 595 high-risk thyroid nodules with continuous volume assessment results and an increase in nodule diameter of less than 3 mm (including all high-risk nodules in patients with single or multiple nodules), 184 (30.9%) and 79 (13.3%) nodules exhibited volume increases of more than 50% and 100%, respectively, in multiple measurements. Among the nodules with volume changes exceeding 50% and 100%, the proportion of nodules with a baseline tumor diameter of≤0.5 cm was significantly higher than those with a diameter of>0.5 cm, at 69.0% vs 31.0% (<0.001) and 77.2% vs 22.8% (<0.001), respectively Active surveillance in patients with highly suspicious subcentimeter thyroid nodules has good short-term oncological outcomes and can be considered a safe alternative to surgery. Due to the large variability in the measurement results of tumor volume, it is not suitable as an indicator for evaluating tumor enlargement