Image of a patient’s neck one day after RFA.
RF Ablation of Benign Thyroid Nodules. The efficacy
of RF ablation for reducing nodule volume and relieving
nodule-related clinical problems was confirmed by the
prospective comparison study by Baek et al. and using a
control group . In five, representative studies, reduction
of the nodule volume after RF ablation ranged from 33–
58% at one month and from 51–85% at six months
postablation [15–17, 20, 22] (Table 1). The greatest volume
reduction is usually observed within the first month after RF
ablation, and further volume reduction is gradually observed
thereafter [15–17, 22] (Figure 2). Recently, the mean volume
reduction rate based on 111 patients with 126 benign thyroid
nodules has been reported to be 93.4% four years following
RF ablation .
For symptomatic cystic (<10% of solid component) nodules, EA should be the first-line treatment modality because of its similar safety and efficacy to those of RF ablation, the fewer number of treatment sessions, and its cost effectiveness; the volume reduction rate was quite similar; 93.1% in EA and 92.2% for RF ablation, as seen at the 6- month followup . In another recent study based on 217 patients with cystic or predominantly cystic nodules, the volume reduction rate was 85.2% at the time of the oneyear followup . For treating predominantly cystic nodules (10% < solid component < 50%), RF ablation is also safe and effective for patients with incompletely resolved clinical problems due to the solid components remaining following EA, which indicates that RF ablation is effective in both solid and cystic thyroid nodules [3, 17, 19, 21, 38]. When the nodules were grouped into mainly cystic, mixed, and mainly solid nodules, the volume reduction was significantly higher for the mainly cystic nodules than for the other types, as seen at the one-month followup. However, at the six-month followup there was no significant difference in the volume in any of the three types . RF ablation is effective in patients with AFTN, as it reduces the nodule volume, improves nodule-related clinical problems, and corrects abnormal thyroid function [14, 16, 20, 22]. RF ablation of AFTNs requires greater effort in order to ablate the entire nodule, including the peripheral area, as untreated portions could interfere with improvements in abnormal thyroid functioning, induce regrowth of treated nodules, and usually require more treatment sessions. Incomplete ablation of nodule margins due to the presence of adjacent critical structures allows marginal regrowth of treated nodules, especially for patients with AFTNs . Although the moving shot technique can successfully prevent marginal regrowth in many patients, undertreated portions adjacent to the danger triangle as well as large-size nodules remain vulnerable to marginal regrowth following RF ablation [2, 16, 22]. A patient with a large thyroid nodule, for example, greater than 20 mL, may require additional RF Figure 1: Schema of the transisthmic approach and the moving shot technique. The needle is inserted through the isthmus in order to visualize the entire length of the electrode and the target nodule. Ablation starts from the deepest portion of the nodule to the superficial area according to the order of the numbering of each small conceptual ablation unit, by moving the electrode tip. The ablation area is small near the peripheral danger triangle (black triangle), while it is large in the central, safe area. Recurrent laryngeal nerve (black circle) is within the danger triangle. The carotid artery (red color), internal jugular vein (blue color), and vagus nerve (gray color) are lateral to each thyroid lobe. ablation due to incomplete treatment and unresolved clinical problems . Thyroid functions are considered to be only minimally influenced by RF ablation, although several anecdotal cases of permanent hypothyroidism after RF ablation have been reported in patients with elevated levels of antithyroid peroxidase antibodies [22, 40]. The possible cause of hypothyroidism seems to be the progression of autoimmune thyroiditis associated with preexisting antibodies. In patients who have previously undergone thyroid lobectomy, RF ablation preserves thyroid functions and therefore seems definitively advantageous over surgery or radioiodine therapy for the treatment of symptomatic benign thyroid nodules . Compared with laser ablation, the long-term volume reduction rate of RF ablation was superior to that of laser ablation, that is, 90–92% in RF ablation versus 48% in laser ablation, as seen in the three-year follow-up data [37, 41]. RF ablation also seems to be safer than laser ablation .