With the increasing incidence of PTMC in recent decades, surgical resection has become the main clinical treatment worldwide[17]. However, traditional excision may cause detachment of the thyroid gland, which may inevitably lead to varying degrees of hypothyroidism[18]. Surgical resection for PTMC often leads to excessive resection and a sense of insecurity in patients, which has been controversial for many years[19, 20]. Some scholars believe that total thyroidectomy for PTMC is unnecessary and expanding thyroidectomy does not improve surgical efficiency[21]. Some academics argue that lymph node metastasis did not affect the survival rates of PTMC patients, and preventive lymph node dissection is unnecessary for those PTMC patients without suspected lymph node metastasis[22–24]. Therefore, in the current clinical environment, an effective minimally invasive treatment of PTMC is urgently needed.
PLA was first used in the treatment of hepatic, uterine and adrenal diseases[25–27]. Pacella et al[28] preliminarily verified the efficacy of PLA to treat benign thyroid nodules. Ultrasound-guided PLA treatment, which has become a promising minimally invasive treatment for thyroid nodules, offers a series of advantages, including simple operation, minimal invasiveness, stable coagulation range, safety, and quick recovery[29]. Døssing et al.[30–32] performed PLA 3 times for 16, 30, and 78 patients with benign cold thyroid nodules and he found that the nodular volume reduction ratios 6 months after PLA were 46%, 44%, and 51%, respectively, suggesting that PLA offers excellent tumor reduction effects. In 2010, PLA was recommended as an effective and safe method for thyroid nodules according to the American Society of Clinical Endocrinologists, the Italian Society of Clinical Endocrinology, and the European Thyroid Association[33]. Therefore, the proper application of PLA in the treatment of thyroid diseases meets the needs of development of modern medicine.
Subjects with malignant thyroid tumors treated by PLA have also been reported in recent years. Lili Ji et al.[34] found that 32.4% of the primary lesions of PTMCs had disappeared, and 64.9% remained as cicatricial hyperplasia; only 2.7% of subjects had cervical lymph node metastasis during the follow-up period after PLA treatment. Zhou W et al.[35] retrospectively analyzed 30 patients with PTMC following PLA treatment and concluded that ultrasound-guided PLA is an effective and safe method for T1N0M0 PTMC treatment of patients who are ineligible for surgical resection.
In the present study, we analyzed 18 PTMC patients undergoing PLA treatment, and our data suggested that all of the nodules of the 18 patients were effectively ablated. CEUS revealed no doppler signal enhancement in the ablation focus after the operation, showing that thyroid nodules were thoroughly removed. No serious complications were found, such as bleeding, dyspnea, or thyroid crisis post-PLA treatment. In addition, no tumor recurrence, cervical lymph node metastasis or distant metastasis were found during the follow-up. To test the ablation efficiency of PLA, we measured the maximum diameter and volume of the ablation areas, and our data suggested that the maximum diameter and volume of the ablation areas at 30 minutes and 1 month after operation were significantly larger than those of the preoperative nodules. In the 3rd month and 6th month after the operation, the maximum diameter and volume of the ablation areas decreased, and no significant differences were found between the post and preoperative nodules. From the 12th month, the maximum diameter and volume of the ablation areas gradually decreased, noticeably smaller than the preoperative nodules.
These findings suggested that ultrasound-guided PLA is a new therapeutic approach that could be an alternative treatment for PTMC.
During the process of PLA treatment, attention should be paid to the following aspects: (1) Hydrodissection solution should be used when the distance between nodules and vital organs is less than 5 mm. (2) The temperatures of the thyroid and vital organs must be monitored: once the temperature is too high, energy output must be reduced. (3) If the nodule adheres to the trachea or blood vessels, the nodule can be ablated partially. (4) If one side of recurrent laryngeal nerve (RLN) is injured, the other side of RLN should be avoided during ablation to avoid asphyxia. Although PLA exhibits considerable clinical efficacy in treating PTMC in the present study, it still must be further improved. (1) More patients and long-term follow-up need to be investigated in the ensuing studies. (2) New imaging techniques, such as computerized three-dimensional stereotaxic technology, could be used to reduce the damage surrounding vital tissues during the PLA process. (3) There are few comparative studies between thermal ablation and surgical resection, which need to be further investigated.