Radiofrequency Ablation: A Novel Treatment Option for Neck Recurrence in Medullary Thyroid Carcinoma

Background: Medullary thyroid carcinoma (MTC) is an aggressive cancer with cervical lymph node metastases typically found at presentation. The recurrence rate after resection is high (~ 50%)(1), and patients often need multiple surgeries. Radiofrequency ablation (RFA) has been used in treatment of recurrent thyroid cancer when surgery is contraindicated or declined by patients in both Asia and Europe (2). We present the first case of an MTC recurrence treated successfully with RFA in North America. Clinical Case: A 43-year-old female with sporadic metastatic MTC, status post total thyroidectomy and multiple neck surgeries, presented with elevated calcitonin level of 630 pg/mL (normal: < 10 pg/mL). Neck ultrasound showed left tracheoesophageal groove mass, measuring 12 mm X 12 mm X 17 mm, consistent with metastatic MTC on cytopathology with calcitonin washout of 16590 pg/mL (normal: < 10 pg/mL). She had no dysphagia, shortness of breath or hoarseness of voice. Computed tomography (CT) scan of chest confirmed presence of mass, in proximity with left recurrent laryngeal nerve. Serial imaging showed rapid enlargement, with concern for impending aerodigestive tract invasion. Surgical intervention had a high risk of vocal cord paralysis due to the lesion’s location. A multidisciplinary tumor board agreed that thermal ablation aimed at shrinking the mass, as a bridge to systemic therapy, would be the best option. RFA was performed as an outpatient with conscious sedation, after informed consent and observing standard aseptic techniques. Under continuous ultrasound guidance, D5W was injected into left tracheoesophageal groove behind the mass and a continuous infusion of D5W at 15 mL/hr was maintained to protect the nerve from thermal injury. Using a trans-isthmic approach, an 18 G monopolar RFA probe with 5 mm active tip was advanced into the malignant mass and ablation was performed with 35 W power until the entire mass was hyperechoic. Vocal response was monitored throughout the procedure and voice remained normal after RFA. A neck ultrasound at her 6 months follow-up showed ablated lesion measuring 7 mm X 11 mm X 10 mm, representing a 68.6% reduction in volume. Repeat CT scan thorax showed disappearance of mass in left neck region. Conclusion: RFA is a minimally invasive and effective treatment for recurrent cervical MTC lesions, and a viable alternative to surgery, as shown in our case. Future studies should focus on long term follow-up and comparison with surgery with regards to safety and efficacy. References: 1.Skoura E. Depicting medullary thyroid cancer recurrence: the past and the future of nuclear medicine imaging. Int J Endocrinol Metab. 2013;11(4):e8156. 2.Garberoglio R, Aliberti C, Appetecchia M, Attard M, Boccuzzi G, Boraso F, et al. Radiofrequency ablation for thyroid nodules: which indications? The first Italian opinion statement. J Ultrasound. 2015;18(4):423-30.