Endocrine Abstracts

Objective: As a measure to reduce overtreatment, active surveillance (AS) for low-risk papillary thyroid carcinoma (PTC) has spread from Japan and gradually become accepted around the world. Older age is known to be a favorable factor for progression under AS; however, long-term evidence is still limited and lifelong monitoring is considered inevitable. The present study reviewed the results of AS from the 1990s and explored the possibility of completing follow-up.

Methods: Patients with low-risk PTC (all T1a, occasional T1b, N0M0) were provided information regarding AS and immediate surgery, and autonomously selected their preferred management option. For patients who chose AS, ultrasound was conducted every 6 or 12 months. Calcification patterns of the tumor were classified into weak (none or micro) and strong (macro or rim). Progression was defined as either tumor enlargement (≥3 mm from the initiation) or development of clinically apparent lymph node metastasis (LNM).

Results: AS was conducted for 650 patients. Mean age at presentation was 53.4 ± 12.8 years and the median duration of follow-up was 8 (range, 1-29) years. During AS, tumor enlargement occurred in 71 (10.9%) patients and 9 (1.4%) patients developed LNM. Overall, 80 (12.3%) patients showed progression. Cumulative rates of progression at 10 and 20 years were 11.5% and 25.3%, respectively. Eventually, 62 (9.5%) patients underwent conversion surgery (31 due to tumor enlargement; 9 due to LNM; 22 due to other reasons), but no patient experienced postoperative recurrence. Multivariate analysis revealed that older age (hazard ratio [HR], 0.98; P = 0.012), male sex (HR, 0.22; P = 0.037), and strong calcification (HR, 0.50; P = 0.045) were significant predictive factors for non-progression. Degree of calcification correlated with patient age and duration of follow-up. Eighty-eight patients who developed rim calcification did not show subsequent progression. Median age and duration of follow-up at the time progression was identified were 55 (range, 24-84) years and 4 (range, 1-20) years, respectively. Only 2 patients showed progression after 15 years of follow-up and 5 patients showed progression after reaching the age of 80 years. The 40 patients who needed conversion surgery due to progression had a median age of 53 (range, 27-81) years, and only 1 patient was over the age of 80 years.

Conclusions: Progression under AS was extremely rare in tumors with rim calcification or old patients (>80 years) with long-term follow-up (>15 years). Intensive monitoring for low-risk PTC might not be necessary for these patients.