ANALYSIS OF POSTOPERATIVE ULTRASONOGRAPHY SURVEILLANCE AFTER HEMITHYROIDECTOMY IN PATIENTS WITH PAPILLARY THYROID MICROCARCINOMA: A MULTICENTER STUDY

Objective: The optimal follow-up interval for postoperative ultrasonography (US) surveillance after hemithyroidectomy in patients with papillary thyroid microcarcinoma (PTMC) is unclear. The purpose of this study was to evaluate the prevalence of tumor recurrence/persistence and to investigate the appropriateness of postoperative US surveillance in PTMC patients who underwent hemithyroidectomy. Methods: Our institutional review board approved this retrospective study. From 2000 to 2011, 800 patients underwent hemithyroidectomy as treatment for PTMC, as well as at least one session of postoperative follow-up US, at four different institutions. The images and data of postoperative US surveillance were retrospectively investigated by experienced radiologists at each institution. Based on the follow-up US and histopathologic results, locoregional tumor recurrence/persistence was determined. Results: Of the 800 patients, 82.2% had T1a, 17.8% had T3, and none had T1b, T2, T4a, or T4b disease; 6.9% had unknown N stage, 80.1% had N0, 13% had N1a, and none had N1b, based on histopathology. There were also no cases of distant metastasis after hemithyroidectomy. Among the patients, 784 (98%) showed no tumor recurrence/ persistence, and 16 (2%) showed locoregional tumor recurrence/persistence during the follow-up period. The patients differed in the number of sessions and the intervals of postoperative follow-up US. In the 16 patients with tumor recurrence/persistence, the mean interval of postoperative follow-up US since the first US detection of tumor recurrence/persistence was 42.9 +/- 25.9 months. All recurrence/ persistence cases were subcentimeter. Conclusion: Postoperative US surveillance at 1or 2-year intervals may be unnecessary because of the very low recurrence rate in PTMC.