Long-term recurrence of small papillary thyroid cancer and its risk factors in a Korean multicenter study

Context: Small papillary thyroid cancer (PTC) generally has an excellent prognosis. However, longterm recurrence is not uncommon and sometimes leads to morbidity or mortality. Objective: To identify high-risk factors for long-term recurrence in patients with small PTC by stratifying their pathologic characteristics. Design, Setting, and Patients: We conducted a nationwide, retrospective, multicenter study of 3282 patients with PTC sized ≤2 cm from 9 high-volume hospitals in Korea. Main Outcome Measures: The maximally selected x² method was used to find the best cutoff points of tumor size, the number of metastatic lymph nodes (LNs), and the ratio of metastatic/examined LNs (LNR) to predict recurrence. Kaplan-Meier analysis and the Cox proportional hazards regression model were used to analyze recurrence and risk factors. Results: The optimal tumor size cutoff was 1.8 cm (10-year recurrence rates for tumors sized 0.1 to 1.7 cm and 1.8 to 2.0 cm: 7.7% vs 17.2%, respectively). Metastatic LNs ≤1 and ≥2 provided optimal estimates of recurrence (10-year recurrence rates: 4.0% vs 16.8%, respectively). The LNR of 0.19 was the optimal cutoff point for predicting the risk of recurrence (10-year recurrence rates for LNRs of 0 to 0.18 and 0.19 to 1: 2.7% vs 16.2%, respectively). LN metastasis, lobectomy, tumor size ≥1.8 cm, and bilateral tumors were independent risk factors for recurrence. Conclusions: Long-term recurrence was increased in patients who underwent lobectomy or with tumor sized ≥1.8 cm, 2 or more metastatic LNs, or bilateral tumors. For patients with these high-risk features, total thyroidectomy could be considered to avoid reoperation.