Ablative therapy for Thyroid Nodule
Thermal ablation utilizing radiofrequency ablation (RFA) and Microwave ablation (MWA), is a new, minimally invasive modality employed as an alternative to surgery in patients with benign thyroid nodules and recurrent thyroid cancers.
Keypoints:
| Indications | A. Benign thyroid nodule - 1. At least two US-guided fine-needle aspirations (FNA) or core-needle biopsy (CNB) before ablation 2. Single benign diagnosis on FNA or CNB is sufficient when - Nodule has US features highly specific for benignity (isoechoic spongiform nodule or partially cystic nodules with intracystic comet tail artifact). - Autonomously functioning thyroid nodule (AFTN) | 1. Symptomatic - pain, dysphasia, foreign body sensation, discomfort, neck bulging, and cough or 2. Cosmetic problems - Cosmetic Score |
| B. Recurrent thyroid cancers at the thyroidectomy bed and cervical lymph nodes | 1. Curative or palliative purposes 2. High surgical risk patients or who refuse surgery. |
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| C. Follicular Neoplasm | 1. Surgery is the standard treatment tool 2. RFA currently reserved for high surgical risk or who are ineligible for surgery |
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| D. Primary Thyroid Cancers | 1. Surgery is the standard treatment tool | |
| Laboratory | 1. Thyroid panel (TSH, thyroid harmone, and thyroid autoantibody level) 2. Thyroglobulin levels in patients with recurrent thyroid cancer after total thyroidectomy 3. Parathyroid hormone, calcium and phosphate level to diagnose hyperparathyroidism. 4. Calcitonin level 5. CBC, Coagulation profile | 1. Anticoagulation / Anti-Platelet should be stopped accordingly prior to the procedure |
| Imaging | 1. Pre procedure USG - evaluate size, volume, characteristic of nodule, composition, vascularity, presence of lymph nodes, relationship of target nodule with other neck structures like vessels and nerves. 2. Aberrant Anatomy like right sided oesophagus, extension of thyroid gland between common carotid and internal jugular vein, location of inferior parathyroid gland, right sided recurrent laryngeal nerve (associated aberrant right subclavian artery), aberrant vagus nerve (anterior and medial) | Additional Imaging: 1. Tc-99m pertechnetate scintigraphy - differentiate cold nodules from AFTNs. 2. CT - for intra-thoracic extent of benign lesions. 3. Parathyroid scan for localising parathyroid nodules. Additional CT or MRI might be required for ectopic parathyroid nodules. |
| Technique | 1. Perithyroidal lidocaine injection is recommended for local anesthesia technique 2. Thyroid nodule is divided into small ablation units 3. Moving-shot technique - ablation of most caudal and posterior portion of nodule so as to avoid disturbances caused by microbubble formation during ablation. | 1. Trans-isthmic approach method - Allows good visualisation of electrode tip and other important structure in neck like vessels and nerves. 2. Cranio-caudal approach - difficulty in determining proximity of electrode tip to important structure in neck like vessels and nerves. 3. Lateral approach - when isthmus has many enlarged vessels |
| Cystic and predominantly cystic nodules | Ethanol ablation (EA) is recommended as the first-line treatment method. | RFA can be recommended as the next step in cases with incomplete resolved symptoms or recurrence following EA |
| Electrode Tip | Electrode with a small active tip - most commonly used is 0.5 cm (available sizes 0.38, 0.5, 0.7, 1 and 1.5 cm) | The electrode tip size is chosen based on the tumor size and status of the surrounding critical structures. |
| Post-procedure | 1. Immediate post-procedure (upto 3-7 days) can show some increased swelling due to odema of surrounding tissue 2. Clinical, Laboratory, and Imaging Evaluation 3. Follow up at 1, 3, 6 and 12 months | 1. Mostly USG neck can help evaluate the patient post procedure (loss of vascularity in ablated nodule, decreased volume, decreased echogenicity) 2. Repeat CT for lesions previously extending into neck 3. Tc-99m pertechnetate scintigraphy is must for AFTN lesions. 4. Recurrent Thyroid cancer - CECT neck at 1 month for look for residual enhancement, USG follow up at 1, 3, 6 and 12 months, thyroglobulin concentration at 6 months. |
| Additional ablation | 1. Large nodule (1-2 months after 1st session) 2. Hyper-functioning thyroid and parathyroid nodules - 2nd session should be performed as early as possible 3. Incomplete resolution of symptoms 4. Reoccurrence - as and when required | |
| Complications (Avoid 2-3 mm width when adjacent to important anatomic structure) | Major complications | 1. Nerve injuries - Recurrent laryngeal nerve (Most common) - Cervical sympathetic ganglion - Horner’s syndrome. - Brachial plexus - sensory and motor disturbance of the arm and fingers - Spinal accessory nerve - asymmetric neckline, drooping shoulder, winging of the scapula (trapezius and sternocleidomastoid muscles involvement) 2. Nodule rupture, and 3. Permanent hypothyroidism 4. Tracheal injury - First symptom is Cough |
| Minor complications | 1. Hematoma (manual compression for 5-10 mins is usually therapeutic), 2. Oesophageal injury - can be avoided by asking the patient to drink cold water 3. Skin burn 4. Transient thyrotoxicosis 5. Lidocaine toxicity 6. Hypertension 7. Pain 8. Edema and swelling (usually resolves in 3-7 days) |
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| Contraindications | No absolute contraindications | Relative contraindications: 1. Uncorrectable coagulopathy 2. Follicular neoplasm |
- Kim, Ji-Hoon et al. “2017 Thyroid Radiofrequency Ablation Guideline: Korean Society of Thyroid Radiology.” Korean journal of radiology vol. 19,4 (2018): 632-655. doi:10.3348/kjr.2018.19.4.632
- Baek JH, Kim YS, Lee D, Huh JY, Lee JH. Benign predominantly solid thyroid nodules: prospective study of efficacy of sonographically guided radiofrequency ablation versus control condition. AJR Am J Roentgenol. 2010 Apr;194(4):1137-42. doi: 10.2214/AJR.09.3372. PMID: 20308523.
- Sung JY, Kim YS, Choi H, Lee JH, Baek JH. Optimum first-line treatment technique for benign cystic thyroid nodules: ethanol ablation or radiofrequency ablation? AJR Am J Roentgenol. 2011 Feb;196(2):W210-4. doi: 10.2214/AJR.10.5172. PMID: 21257865.
- Moon WJ, Baek JH, Jung SL, Kim DW, Kim EK, Kim JY, Kwak JY, Lee JH, Lee JH, Lee YH, Na DG, Park JS, Park SW; Korean Society of Thyroid Radiology (KSThR); Korean Society of Radiology. Ultrasonography and the ultrasound-based management of thyroid nodules: consensus statement and recommendations. Korean J Radiol. 2011 Jan-Feb;12(1):1-14. doi: 10.3348/kjr.2011.12.1.1. Epub 2011 Jan 3. PMID: 21228935; PMCID: PMC3017873.
- Giovagnorio F, Martinoli C. Sonography of the cervical vagus nerve: normal appearance and abnormal findings. AJR Am J Roentgenol. 2001 Mar;176(3):745-9. doi: 10.2214/ajr.176.3.1760745. PMID: 11222217.
- Ha EJ, Baek JH, Lee JH, Kim JK, Shong YK. Clinical significance of vagus nerve variation in radiofrequency ablation of thyroid nodules. Eur Radiol. 2011 Oct;21(10):2151-7. doi: 10.1007/s00330-011-2167-6. Epub 2011 Jun 2. PMID: 21633824.
- Sung JY, Baek JH, Kim YS, Jeong HJ, Kwak MS, Lee D, Moon WJ. One-step ethanol ablation of viscous cystic thyroid nodules. AJR Am J Roentgenol. 2008 Dec;191(6):1730-3. doi: 10.2214/AJR.08.1113. PMID: 19020243.