The results of active surveillance with ultrasonography in papillary thyroid cancer with excellent response to therapy

Due to the development of technology in the area of medical imaging, there has been an increase in the detection of incidental papillary thyroid cancer during diagnostic imaging for other diseases. However, most of the incidental papillary thyroid cancer has been stratified as low risk. It has been shown that dynamic risk stratification (DRS) is a better predictor of the risk of recurrence than the ATA risk stratification system. Thus, more current studies address concerns about the optimum active surveillance of papillary thyroid cancer stratified as low risk by the DRS system. This study aims to investigate the true recurrence risk of DRS subgroups and the efficiency of active ultrasound surveillance in detecting recurrences. Our study included 398 patients who have undergone a total or completion thyroidectomy and been surveilled for at least 3 ultrasound scans. The reports of three consecutive periodic ultrasound scans following the initial assessment were analyzed retrospectively. Ultrasonography results were evaluated based on European Thyroid Association (ETA) guideline criteria. Considering parameters such as microcalcification, roundness index, type of vascularity, presence of hilum, and level of echogenicity, sonography findings were categorized as suspicious, indeterminate, or benign. If the sonographic finding did not meet any of these criteria, it was defined as a non-specific lesion. In addition, the positive predictive value (PPV) and negative predictive value (NPV) of the follow-up ultrasound scans were calculated. The median surveillance time was 81 months (30-240). Only 8 recurrences were observed. The recurrence rate was found to be 0.4% in the excellent response group. The longest time from therapy response assessment to recurrence in the excellent response group and the non-excellent group was 1 and 2 years respectively. Out of 9 biopsies carried out for atypical findings in the excellent group, only one revealed metastasis whereas the ratio was %100 for the structural incomplete response group. All of the atypical lesions that could not be defined as indeterminate or suspicious by ETA, turned out to be false positive. The three-year cumulative PPV of the study cohort and the non-excellent group was found to be 2% and 31% respectively. Considering the recurrence was seen only in the first year of assessment in the excellent group, PPV of the first periodic ultrasound scans was evaluated. It was found to be 10% in the study cohort and 30% in the non-excellent sub-group. This study recommends that following the first year after the assessment of therapy response, active surveillance for papillary thyroid cancer patients with achieved excellent response should be with clinical examination and serum non-stimulated thyroglobulin level.