INTRODUCTION: Active surveillance (AS) for low-risk papillary thyroid carcinoma (PTC) is acknowledged as a valid management strategy. While older age is identified as a favorable factor for progression, long-term evidence is scarce and lifelong monitoring has been deemed essential. This study investigated progression patterns and tumor calcification under long-term AS and explored the possibility of ending follow-up. MATERIALS AND METHODS: A total of 650 patients with low-risk PTC who chose AS were enrolled. Progression was defined as either tumor enlargement (≥3 mm from initiation) or development of clinically apparent lymph node metastasis. RESULTS: The median observation period was 8 years
45.2% were under surveillance for ≥10 years. Overall, 80 patients (12.3%) exhibited progression. Median age and observation period at the time of progression were 55 and 4 years, respectively. Only 2 patients showed progression after 15 years of follow-up and 5 patients showed progression after reaching 80 years old. Among 71 patients experiencing tumor enlargement, surgery was performed immediately in 32 patients. The remaining 39 patients continued surveillance, but only 5 demonstrated ongoing enlargement thereafter. Of 40 surgeries due to progression, 36 were conducted within the first 10 years. The degree of calcification correlated with age and observation periods. No progression occurred after the development of rim calcification. CONCLUSIONS: Progression during AS was extremely rare in older patients with long-term surveillance and in tumors with rim calcification. It may be feasible to consider ending scheduled surveillance visits for these patients. Instances of progression halting after enlargement are not uncommon.