*3.4. Lack of an Independent Role of Operative Extent in Patients with Other Risk Factors*

Subgroup analyses were performed to assess the impact of the operative extent in multifocal PTC patients with several risk factors. We examined 3 factors that might influence the recurrence of PTC: primary tumor size (≤1 cm or >1 cm), LN metastasis (node-negative or node-positive), and ATA risk of recurrence (low or intermediate).

Papillary thyroid microcarcinoma (PTMC; defined as PTC ≤ 1 cm) was found in 476 patients, and 143 patients had PTC larger than 1 cm (non-PTMC). The recurrence rates of the total thyroidectomy and lobectomy groups were 6 of 476 (1.1%) and 2 of 99 (2.0%; *p* = 0.469), respectively, for PTMC patients and 2 of 127 (3.2%) and 0 of 16 (0.0%; *p* = 0.467), respectively, for non-PTMC patients. Kaplan–Meier analysis also indicated that total thyroidectomy showed comparable RFS to that of thyroid lobectomy in both the PTMC (*p* = 0.443) and non-PTMC (*p* = 0.711) groups (Figure 2A,B).

**Figure 2.** Recurrence-free survival in patients with (**A**) PTMC and (**B**) non-PTMC.

There were 490 patients with node-negative PTC, and LN metastasis was diagnosed in 225 patients. In the node-negative group, recurrences were observed in 2 of 404 pa-

tients (0.5%) after total thyroidectomy and 1 of 89 patients (1.1%) after thyroid lobectomy (*p* = 0.490). In the node-positive group, 6 of 199 patients (3.0%) with total thyroidectomy and 1 of 26 patients (3.8%) with thyroid lobectomy developed recurrences (*p* = 0.818). RFS was not considerably different between total thyroidectomy and thyroid lobectomy in both the node-negative (*p* = 0.447) and node-positive (*p* = 0.536) groups (Figure 3A,B).

**Figure 3.** Recurrence-free survival in patients with (**A**) node-negative and (**B**) node-positive PTC.

When we stratified patients according to the ATA risk of recurrence categories, 324 and 394 patients were classified as low risk and intermediate risk, respectively. In ATA low-risk patients, recurrence rates were comparable between the total thyroidectomy and lobectomy groups (0.4% vs. 1.5%; *p* = 0.297). Patients with ATA intermediate risk also showed no difference in the recurrence rates be-tween groups (2.0% vs. 2.0%; *p* = 0.996). Total thyroidectomy and lobectomy demonstrated similar RFS in the ATA low-risk (*p* = 0.411) and ATA intermediate-risk (*p* = 0.682) groups (Figure 4A,B).

**Figure 4.** Recurrence-free survival in patients with (**A**) ATA low risk and (**B**) intermediate risk.
