The Coming of Age of Ultrasound-Guided Percutaneous Ethanol Ablation of Selected Neck Nodal Metastases in Well-Differentiated Thyroid Carcinoma

The majority of patients with well-differentiated thyroid cancer (WDTC), whether derived from the follicular cell or the C-cell, present with a focal, often palpable, intrathyroidal primary lesion, but at initial diagnosis, many such tumors have already spread to regional lymph nodes, mainly in the neck (1). The prevalence of such neck nodal metastases (NNM) at presentation varies significantly among the various histological subtypes of WDTC but approaches 40% (2) in both papillary thyroid cancer (PTC) and medullary thyroid cancer (MTC). A significant number of WDTC patients, despite potentially curative primary surgery, are also found to have NNM discovered at months to years after the date of the initial operation. Historically, postoperative “recurrence” within 30 postoperative years occurs in NNM, despite apparently complete primary surgical resection, in 9–20% of PTC and about 25% of MTC patients (2, 3). As detection limits of tumor markers progressively diminish, and high-resolution ultrasound (US) allows the identification of NNM as small as 2–3 mm diameter, increasing numbers of tiny NNM are being confirmed (4) by USguided biopsy (USGB). What to do with such nonthreatening disease is a dilemma increasingly faced by thyroidologists in contemporary clinical practice (5, 6). Clearly, radioiodine remnant ablation (RRA) rarely prevents the discovery of postoperative NNM in follicular cell-derived cancers (FCDC), and reoperative compartment-oriented surgery, recommended by most clinical management guidelines (5, 6) produces a biochemical remission in PTC only 30–50% of the time (7–9). Stereotactic radiotherapy has recently been employed in Korea to treat recurrent NNM in WDTC, but follow-up in these patients (7 PTC; 2 MTC) has been short, and new metastases in 4 of 9 patients developed in “nontarget regional nodes” (10). In this issue of JCEM, a study from Norway (11) describes the latest chapter in a series of papers (12– 15) describing the efficacy of ultrasound-guided percutaneous ethanol ablation (UPEA) in treating NNM in WDTC. Ultrasound-guided percutaneous ethanol injections (UPEI) have been employed since the 1980s for the palliative treatment of small hepatocellular carcinomas. In 1988, UPEI was successfully employed by Charboneau and Hay at the Mayo Clinic (16) to ablate a parathyroid adenoma, which had resulted in persistent hyperparathyroidism in an elderly patient considered unsuitable for neck re-exploration. By 1990, UPEI was being employed in many European centers to treat autonomously functioning thyroid adenomas (17), and it had also been used to treat an inoperable FCDC (18). UPEA was first used at the Mayo Clinic in 1991 to treat two left central compartment NNM (9 mm and 1.1 cm diameter) in a 46-yr-old psychiatrist with stage IV MTC who had undergone three prior neck surgeries, had previously undergone transection of his right recurrent laryngeal nerve and was facing a possible tracheostomy, if he were to undergo further surgical resection. His two injected level VI nodes disappeared on careful US scanning within 10 months and did not recur after 20 yr of follow-up (Hay, I. D., and J. W. Charboneau, unpublished data).