When is percutaneous ablation (PA) recommended for a thyroid nodule?

Percutaneous Ablation for Thyroid Nodules: Clinical Indications

Percutaneous thermal ablation is recommended for symptomatic benign thyroid nodules causing compression symptoms, cosmetic concerns, or anxiety, and for select T1aN0M0 papillary thyroid carcinomas, with all patients requiring pre-procedure fine-needle aspiration biopsy to confirm pathological diagnosis. 1, 2

Primary Indications for Benign Nodules

Absolute Indications

• Symptomatic nodules causing compression symptoms including dysphagia, dyspnea, or neck discomfort 2, 3
• Cosmetic concerns with visible neck enlargement causing patient distress 2, 3
• Autonomously functioning thyroid nodules (toxic adenomas) 2
• Recurrent nodules after previous chemical ablation 2
• Nodules ≥2 cm that are symptomatic, where thermal ablation serves as an alternative to surgery 3

Technical Requirements

• Nodules must be solid or cystic with ≥10% solid composition to be appropriate candidates 2
• Mandatory pre-procedure FNAB confirming benign pathology (Bethesda II) is required before ablation 2

Indications for Malignant Nodules

Papillary Thyroid Carcinoma (PTC)

• T1aN0M0 PTCs are recognized candidates for thermal ablation, leading to in situ tumor inactivation 1
• This indication has been recognized by multiple international guidelines, though the Chinese guidelines note that high-level evidence for PTCs with relative indications is still awaited 1

Patient Selection Criteria

Pre-Procedure Assessment

• Complete laboratory testing including comprehensive blood count, blood type, coagulation function, blood biochemistry, and tumor markers 2
• Ultrasound evaluation of thyroid and cervical lymph nodes, with contrast-enhanced ultrasound (CEUS) to assess blood supply 2
• TSH monitoring to identify autonomously functioning nodules 3

Exclusion Criteria

• Prior FNA results of suspicious or malignant (Bethesda V-VI) require definitive surgical management regardless of size 3
• Uncertainty about malignancy potential makes thermal ablation inappropriate; surgery remains the gold standard 4

Clinical Outcomes and Effectiveness

Volume Reduction

• Thermal ablation achieves complete necrosis of lesions with gradual volume reduction, alleviating symptoms and potentially achieving partial or complete cure 1
• Long-term data shows 47.8% volume reduction at 3 years with improvement in symptoms in 73% of patients 5
• More recent data demonstrates 52.3% volume reduction with 78% patient-reported symptom resolution at 6-month follow-up 6
• Newer techniques like nanosecond pulsed field ablation show 85.8% volume reduction at 1 year with rapid symptom relief as early as 2 weeks 7

Safety Profile

• Thermal ablation is increasingly recognized as safe and effective with widespread acceptance for benign nodules 1
• Thermal damage is restricted to the ablated area with no involvement of nearby parenchyma, as confirmed by histopathological studies 8
• Major complications are rare, with nerve injury risk reduced by adequate hydrodissection (strong recommendation) 1

Common Pitfalls and Caveats

Critical Safety Measures

• Adequate hydrodissection is mandatory to reduce nerve injury risk 1
• NSAIDs are recommended for prevention/treatment of nodular rupture in larger nodules 1
• Nodule rupture occurs in 0.08-0.21% of cases; early NSAID administration improves prognosis 1
• Vasovagal reflex is more common with large nodules compressing carotid vessels; immediate cessation and head-down positioning are required 1

Follow-Up Protocol

• CEUS evaluation post-ablation to confirm complete ablation and assess treatment effectiveness 2
• Initial follow-up at 1 month, then at 3,6, and 12 months during the first year 4
• Monitor volume reduction rate (VRR) to assess treatment efficacy 2
• Approximately 9% of nodules may regrow above baseline, requiring consideration for alternative management 5

When to Choose Surgery Instead

• Growing nodules with documented increase of ≥50% volume or ≥20% in two dimensions warrant surgical intervention 4
• Indeterminate cytology (Thy3/Bethesda III-IV) after ablation requires surgical management for definitive diagnosis 8
• Surgery provides definitive diagnosis and treatment in a single procedure and remains the gold standard when malignancy cannot be excluded 4