The incidence of postoperative re-stratification for recurrence in well-differentiated thyroid cancer—a retrospective cohort study

Background: After diagnosing well-differentiated thyroid cancer (WDTC), assessment of the risk for disease-specific recurrence is essential for deciding between hemi-thyroidectomy (HT) and total thyroidectomy (TT). The American Thyroid Association (ATA) 2015 guidelines suggest that patients with 1-4 cm WDTC without suspicious features may be suitable for HT. Patients' preoperatively determined risk levels are re-stratified according to surgical and final histopathological findings. The incidence and clinical implications of high-risk features discovered postoperatively in patients with preoperatively determined low-risk WDTC are yet to be better defined. Methods: Thyroidectomies performed in the Tel-Aviv Sourasky Medical Center (TASMC) [2006-2018] were included. Patients with 1-4 cm WDTC without evidence of positive cervical lymph nodes, invasion to adjacent structures, or high-risk cytology were considered at low risk for disease-specific recurrence— suitable for lobectomy. Patients were stratified according to their risk for disease-specific recurrence, pre-and postoperatively, and the rate of completion thyroidectomy was determined. Results: In total, 301 (21%) patients were preoperatively stratified as low risk. Forty-six of them (15%) were re-stratified postoperatively as intermediate-to-high-risk. There were no significant differences in the characteristics of the patients who maintained their original stratification to patients who were upscaled to a higher risk level postoperatively. Conclusions: We report a 15% rate of postoperative risk escalation of patients who required completion thyroidectomy according to current ATA guidelines. In our opinion, this rate of postoperative WDTC upscaling of risk requiring more radical surgery than originally planned, is acceptable. Meticulous preoperative personalized evaluation by an experienced multidisciplinary dedicated team is essential.