Ultrasound-Guided Radiofrequency Ablation of Low-Risk Papillary Thyroid Microcarcinoma: a Prospective Study

Abstract

Low risk papillary thyroid microcarcinoma (PTMC) has a high incidence and a good prognosis. Surgical operation to all PTMC has been questioned as over treatment and active surveillance is recommended as an alternative. However, some patients have heavy mental burden and minimally invasive treatment could be used to eliminate PTMC and reduce the tumor related risk of growth and metastasis. The objective of this study was to evaluate the efficacy and safety of ultrasound (US)-guided radiofrequency ablation (RFA) of low-risk PTMC on a large scale of patients with over 1 year follow-up. 421 patients with 440 low risk PTMC were included in this study. US and contrastenhanced ultrasound (CEUS) examinations were performed before ablation. RFA was performed using the movingshot technique. The ablation area exceeded the tumor edge to prevent marginal residue and recurrence. Patients were followed at 1, 3, 6, and 12 months and every six months thereafter. US and CEUS examinations were used to evaluate the ablation area and cervical lymph nodes. The mean volume reduction ratio (VRR) was 0.58±0.09, 0.79±0.07, 0.87±0.05, 0.94±0.04, and 0.96±0.01 at 1, 3, 6, 12, and 18 months after RFA, respectively. Of all the nodules, 172 (39.1%) resolved in six months, and 415 (94.3%) resolved in 12 months. No residual lesion was detected in ablation area. 82 patients were followed up for more than 3 years and the rest patients were followed up for at least 1 year. During follow up, 4 patients had biopsy proved recurrent PTMC in other parts of thyroid tissue, which had diameter of 2mm-3mm and received a second RFA. 5 patients had suspicious thyroid lesions less than 2mm and continued follow up. 4 patients had biopsy proved cervical lymph node metastasis and received RFA of the lymph nodes. No distant metastasis was detected in these patients. And no major complications were encountered. RFA can effectively eliminate low risk PTMC with a very small complication rate. Very low recurrent PTMC and cervical lymph nodes were detected, which could be treated by second RFA. RFA may be an alternative strategy for the treatment of low risk PTMC, especially in patients with heavy mental burden.