What is the process for undergoing thyroid ablation with an interventional radiologist?

Thyroid Ablation with Interventional Radiology: Process and Patient Selection

Thyroid ablation by interventional radiology is a minimally invasive, ultrasound-guided thermal procedure that serves as an alternative to surgery for select benign thyroid nodules and, in specific circumstances, for recurrent well-differentiated thyroid cancers, requiring careful patient selection, pre-procedural imaging, informed consent, and structured follow-up. 1, 2

Pre-Procedural Patient Assessment

Diagnostic Confirmation

• All patients must undergo fine-needle aspiration biopsy (FNAB) to confirm pathological diagnosis before thermal ablation 1
• Core needle biopsy may be considered as an alternative diagnostic method 1
• For suspected lymph node involvement (loss of fatty hilum, cystic changes, microcalcifications, hypervascularity), cytological or histological examination with thyroglobulin detection of aspirate should be performed 1

Laboratory Evaluation

• Thyroid function tests (TSH, free T3, free T4) are required, particularly for autonomously functioning nodules 1, 3
• Thyroid antibody assessment if diffuse thyroid disease is suspected 1
• Serum thyroglobulin and anti-thyroglobulin antibodies for malignant cases 1

Imaging Requirements

• Comprehensive neck ultrasound to assess nodule characteristics, size, location, and relationship to critical structures 1, 2
• Contrast-enhanced ultrasound (CEUS) to evaluate nodule vascularity and plan ablation zones 1
• Assessment of cervical lymph node chains bilaterally 1

Patient Selection Criteria

Benign Nodules - Strong Indications

Thermal ablation is recommended for benign thyroid nodules meeting any of these criteria: 1

• Nodules causing compression symptoms (dysphagia, dyspnea, pain)
• Nodules causing cosmetic concerns or anxiety
• Nodules ≥2 cm with progressive growth
• Autonomously functioning thyroid nodules causing hyperthyroidism 1, 3
• Recurrent nodules after chemical ablation 1

Malignant Nodules - Relative Indications

For papillary thyroid carcinoma (PTC) without lymph node or distant metastases (cN0M0), thermal ablation may be considered when: 1

• Single cancer nodule ≤1 cm in maximal diameter
• Cancer nodule located in the thyroid isthmus
• Cancer nodule adjacent to or invading the thyroid capsule
• Cancer nodule 1-2 cm in maximal diameter
• Multiple cancer nodules (≤3 nodules, each ≤1 cm)
• Patient refuses surgery or has prohibitive surgical comorbidities 1, 4

Thermal ablation is also an option for recurrent thyroid cancer and limited metastatic cervical lymph nodes 1, 5

Absolute Contraindications

• Severe bleeding disorders 1
• Severe cardiopulmonary insufficiency or inability to cooperate 1
• Contralateral vocal cord paralysis 1
• Diffuse sclerosing papillary carcinoma 1
• Malignant pathology other than PTC 1
• Pregnancy and lactation (relative contraindication) 1

Procedural Details

Anesthesia and Approach

• Local anesthesia with 1-2% lidocaine is standard 1
• Needle insertion via the thyroid isthmus or lateral neck approach 1
• Hydrodissection technique using 0.9% sodium chloride (for microwave ablation) or sterile distilled water/5% glucose (for radiofrequency ablation) to protect recurrent laryngeal nerve, trachea, esophagus, and major vessels 1

Ablation Techniques

• Moving-shot technique to ensure complete ablation while minimizing complications 1
• Real-time ultrasound monitoring throughout the procedure 1, 2
• Immediate post-ablation CEUS to assess non-perfused zone extent 1

Expected Outcomes for Benign Nodules

• Volume reduction of 33-58% at 1 month and 51-85% at 6 months 5, 6
• Average volume reduction rate (VRR) of approximately 61% within 3-6 months 3
• Resolution of hyperthyroidism in 90.9% of autonomously functioning nodules after single session 3

Post-Procedural Management and Follow-Up

Follow-Up Schedule

• First follow-up at 1 month, then at 3,6, and 12 months during the first year 1
• After 12 months: every 6 months for malignant nodules, annually for benign nodules 1

Follow-Up Components

• Grayscale ultrasound and CEUS to assess ablation zone and detect residual/recurrent disease 1
• Volume reduction rate calculation: VRR = [(Pre-ablation volume - Post-ablation volume) × 100]/Pre-ablation volume 1
• Assessment of symptom improvement using validated instruments 1
• Thyroid function tests, particularly for autonomously functioning nodules until normalization 1

TSH Suppression for Malignant Nodules

Following thermal ablation of malignant thyroid nodules, TSH suppression therapy is recommended: 1

• Target TSH 0.5-2.0 mU/L for nodules meeting absolute indications
• Target TSH <0.5 mU/L for nodules meeting relative indications
• Monitor at 3,6, and 12 months initially, then every 6 months once controlled 1

Management of Residual or Recurrent Disease

• Confirmed residual or recurrent malignant nodules require prompt supplementary treatment 1
• Monitor ipsilateral and contralateral cervical lymph nodes with FNAB when indicated 1

Complications and Safety Profile

Common Side Effects

• Pain (most frequent, up to 100% incidence) - typically transient and self-limiting 1
• Mild discomfort in neck, jaw, teeth, ears, or shoulder 1

Minor Complications

• Bleeding/hematoma (0.35-17% incidence) - usually manageable with local compression 1
• Transient voice changes (0.5-7.9%) - typically resolve within 1-3 days 1
• Transient tachycardia requiring short-term beta-blockers (9%) 3
• Mild hypothyroidism requiring levothyroxine (9%) 3

Major Complications (Rare)

• Permanent vocal cord paralysis (0.04-0.17%) 1
• Sympathetic ganglia or brachial plexus injury (0.04-0.08%) 1

Important caveat: The evidence for thermal ablation of primary thyroid cancer is still evolving, with most data from Asian populations and shorter follow-up periods compared to traditional surgery 4, 2. For differentiated thyroid cancer, surgery followed by radioiodine ablation remains the standard of care for most patients, particularly those with high-risk features 1. Radioiodine ablation using recombinant human TSH (rhTSH) preparation while on levothyroxine is the established method for post-surgical remnant ablation in appropriate candidates 1.