A Novel Approach to Recurrent Papillary Thyroid Carcinoma – Radiofrequency Ablation

Although papillary thyroid cancer (PTC) has a favorable prognosis, reoccurrence in the neck region can range between 20% in low risk tumors to 59% in high risk tumors. To add, in these reoccurring tumors, repeated surgeries can be challenging. Novel image-guided percutaneous interventions for thyroid tumors such as radiofrequency ablation (RFA) has been studied in solitary and reoccurring PTC with favorable results. This case describes a patient with reoccurring PTC who underwent radiofrequency ablation.

Case Description :

This is a case of a 68 year old Caucasian male with a significant past medical history of recurrent papillary thyroid cancer. His initial diagnosis of papillary thyroid cancer was found one year ago, after a total thyroidectomy with left inferior parathyroidectomy was performed for compressive multinodular goiter and left inferior parathyroid adenoma. Prior to his surgery he had fine needle aspiration cytologies of multiple nodules that were negative for thyroid cancer. His postoperative pathology diagnosis was multifocal bilateral papillary thyroid cancer – classical type - with lymph node metastasis (pathological stage: mpT1b pN1a). Serum thyroglobulin was 4.9 ng/mL (reference range 1.6 – 59.9 ng/mL). Therefore, as the patient was deemed American Thyroid Association (ATA) intermediate risk, he was given adjuvant radioactive iodine (I-131 120mCi) treatment. Subsequent to this, he was started on suppressive levothyroxine at 250 µg daily for TSH suppression, with pretreatment TSH at 14.730 µU/mL and TSH after 4 months of treatment 0.140 µU/mL.

Four months after I-131 therapy, a neck exam revealed a palpable firm lymph node in the upper right neck. A diagnostic ultrasound revealed this to be a right level IIb cystic cervical lymph node (18 x 16 x 18 mm) with no overt vascularity. Serum thyroglobulin at this time (four months post I-131 therapy) was < 0.2 ng/mL. He then underwent fine needle aspiration biopsy, with cytology showing papillary thyroid carcinoma. Thyroglobulin measured in the needle washout was elevated (1015.3 ng/mL, reference range < 10ng/mL). Due to the nature of the recurrent cancer, as well as the surgical risks, radiofrequency ablation of the metastatic lymph node was performed.
Six weeks post ablation, a surveillance ultrasound showed an 80% reduction (11 x 8 x 12 mm) in node size, with decreased cystic appearance and no vascularity. The patient denies any complications after the ablation.

Discussion :

Radiofrequency ablation is an image guided therapeutic technique that uses alternating current of frequencies ranging between 200 kHz and 1200 kHz to generate heat (50 - 100°C) leading to coagulative necrosis. This technique, first introduced for thyroid nodules in the early 21^st-century, has rapidly gained popularity in the treatment of benign and malignant thyroid tumors due to its minimally invasive nature and low complication rate. So far, studies unanimously report a volume reduction rate (VRR) of greater than 50%, with some studies reporting almost 99% VRR within 12-24 months. Studies specific to recurrent nodes were also favorable, suggesting a role for RFA to replace 'berry picking surgery’ in selected patients.