Active surveillance for a small low-risk papillary thyroid cancer: a 10-year prospective, observational study in an Italian tertiary care centre.

Objective: To evaluate the long-term safety and feasibility of active surveillance (AS) for Italian patients with low-risk papillary thyroid microcarcinoma (mPTC) and to analyse trends in patient enrolment and factors associated with discontinuation of surveillance. This study represents the first prospective European investigation with long-term follow-up assessing AS for mPTC. Design: Prospective, observational, non-randomised study with a duration of 10 years (2014-2024). Setting: Single tertiary referral centre (University Hospital of Pisa, Italy). Participants: 260 adult patients with a mPTC (≤13 mm) who voluntarily opted for AS instead of immediate surgery. Interventions: AS consisting of periodic clinical evaluation and neck ultrasonography every 6 months for the first 2 years and annually thereafter. Surgery was recommended only in the presence of predefined disease progression or at patient request. Main outcome measures: Rates of disease progression, delayed surgical intervention, oncologic outcomes after surgery and patient discontinuation of AS. Results: A total of 260 patients were enrolled and followed for up to 10 years. Disease progression occurred in approximately 5% of patients. All patients who underwent delayed surgery achieved excellent outcomes, with no evidence of recurrence after a median postoperative follow-up of 43.5 months. No disease-specific deaths occurred during AS or after surgery. Over the study period, patient enrolment progressively increased, reflecting growing acceptance of AS. However, 18.5% of patients discontinued surveillance without evidence of progression, most frequently within the first year. Younger age and cytology suspicious for malignancy were associated with higher dropout rates. Conclusions: This study provides the first long-term prospective evidence that AS is a safe and feasible management strategy for patients with mPTC also in a European country. These findings support AS as a valid first-line approach and reinforce the need for improved patient education to optimise adherence and reduce unnecessary surgery.