Clinical Effects of Microwave Ablation in the Treatment of Low-Risk Papillary Thyroid Microcarcinomas and Related Histopathological Changes

Abstract

ObjectiveThis study aimed to evaluate the feasibility and efficacy of ultrasound-guided percutaneous microwave ablation (MWA) in the treatment of low-risk papillary thyroid microcarcinoma (PTMC), and to observe the histopathological changes after MWA.MethodsMWA was performed under ultrasound guidance for 73 unifocal PTMC patients without clinically cervical or distant metastasis. The target ablation zone exceeded the tumor edge (judged by contrast-enhanced US) to avoid marginal residue and recurrence. Ultrasound evaluation was performed at 1 day, 1, 3, 6, 12 and 24 months after treatment, and thyroid function evaluation at the first 6 months. Repeated fine needle aspiration cytology or core needle biopsy pathology was performed at 3 or 6 months after MWA to evaluate residual tumors. Any adverse event associated with MWA was evaluated.ResultsThe follow-up after MWA lasted 6 (6, 12) months. Tumor volume decreased significantly from 0.06 mm3 (0.04, 0.11 mm3) to 0.03 mm3 (0.00, 0.06 mm3) at 12 months after MWA (P< 0.001), with a median volume reduction ratio of 80.28% (-7.43, 100%) and 16 cases (21.92%) presenting complete remission. The largest diameter, volume and ablation energy were found to be different in patients with and without complete remission 12 months after MWA. On histopathological examinations, no atypical or malignant follicular cells were identified after thermal ablation. The most common pathological characteristics were fibroblastic proliferation (34/39, 87.18%) and chronic inflammation (32/39, 82.05%), followed by infarction (21/39, 53.85%). Five patients were transferred to thyroidectomy and 4 of them were confirmed with local recurrence and/or lymph node metastasis. Serum thyrotropin decreased transiently after MWA (P< 0.01) but normalized thereafter. No serious and permanent complications were reported.ConclusionsMWA is a safe and effective treatment for low-risk PTMC. Fibroblastic proliferation and chronic inflammation are the most common pathological changes after MWA of PTMC.

Pathology confirmation of the efficacy and safety of microwave ablation in papillary thyroid carcinoma

“…Lu et al. ( 15 ) also reported that no characteristics of PTC were found by FNA and CNB at the 3 months and 6 months follow-up in 44 patients with unifocal micro-PTC who underwent MWA. In other studies, the local recurrence rate after MWA treatment was also very low ( 16 – 18 ).…”

Clinical application status and prospect of the combined anti-tumor strategy of ablation and immunotherapy

“…MWA is another novel tumor ablation technology which developed from biologic thermal effects, which is mainly applied in the treatment of solid tumors in liver ( 40 ), lung ( 41 ), kidney ( 42 ), adrenal gland ( 43 ), spleen ( 44 ), thyroid ( 45 ) and breast ( 46 ). The therapeutic effects of MWA depends on the dipolar molecules (primarily water) to align and realign according to the variable electromagnetic field.…”

Hyperthermia combined with immune checkpoint inhibitor therapy in the treatment of primary and metastatic tumors

“…Coagulative necrosis often occurs in the central area, leading to the release of new antigens in tumor cells, which is called tumor in situ vaccination, while the transition zone is easily affected by residual temperature, resulting in secondary effects such as immune activation (17). However, the latest research shows that thermal ablation not only irreversibly denatures the newly released antigens in the central area of tumor tissues but may also upregulate some carcinogenic factors (such as interleukin-6(IL-6) and vascular endothelial growth factor(VEGF)), aggravating the progression of tumor metastasis (18,19). However, thermal ablation still has some positive immunomodulatory effects, such as the release of positive immunomodulatory factors, initiation of a local inflammatory response, and recruitment of immune cells (18,20).…”

“…However, the latest research shows that thermal ablation not only irreversibly denatures the newly released antigens in the central area of tumor tissues but may also upregulate some carcinogenic factors (such as interleukin-6(IL-6) and vascular endothelial growth factor(VEGF)), aggravating the progression of tumor metastasis (18,19). However, thermal ablation still has some positive immunomodulatory effects, such as the release of positive immunomodulatory factors, initiation of a local inflammatory response, and recruitment of immune cells (18,20). Compared with thermal ablation, the main effect of mild hyperthermia is not necrosis, but apoptosis, vascular permeability, and immune effect.…”