HOUSTON — Ultrasound-guided minimally invasive procedures are being used increasingly to induce clinically significant shrinkage of benign symptomatic thyroid nodules.
At the annual meeting of the American Association of Clinical Endocrinologists, Dr. Enrico Papini described his experience with the procedures. Ultrasound (US)-guided percutaneous ethanol injection (PEI) was actually the first procedure developed for office-based debulking of benign thyroid lesions and is currently indicated for cystic lesions. However, despite its advantages of low cost and good tolerability, it has been shown to have significant technical limitations in cold nodules and a high risk of relapse in hyperfunctioning nodules.
“Novel percutaneous image-guided procedures are needed for nonsurgical cytoreduction of thyroid lesions,” said Dr. Papini of the endocrinology and metabolism department at Regina Apostolorum Hospital, Rome.
Minimally invasive strategies with the use of thermal energy sources such as laser, radiofrequency, microwave, high-intensity focused US, and cryotherapy are receiving more attention for the treatment of benign and malignant tumors.
With percutaneous laser ablation (PLA), tissue is converted to heat by the light from a source such as a 1,064-nm Nd:YAG laser or continuous wave infrared diode laser, introducing a zone of necrosis with well defined margins. Spinal needles are inserted into the thyroid lesion which is then directly targeted with the laser. It is an outpatient procedure because pain is usually mild and evaporates soon after the end of illumination, he said.
In contrast to PEI, PLA induces a fairly predictable area of necrosis, thereby reducing side effects and damage to surrounding cervical structures. Two randomized clinical trials of PLA showed that the treatment induces a median reduction in nodule volume of over 40% and a decrease in local pressure symptoms (Eur. J. Endocrinol. 2005;152:341-5; Thyroid 2007;17:229-35).
Local symptoms and volume decrease were stable during 6- and 12-month follow-ups with PLA, which was found to be more effective than long-term levothyroxine therapy in inducing nodule shrinkage and improvement in local symptoms. In contrast, clinical control with no active treatment was associated with a high probability of further nodule growth and symptom progression, Dr. Papini said, referring to his study (Thyroid 2007;17:229-35).
Adverse effects reported in the various series have included isolated cases of transient dysphonia, lasting from 1 week to 2 months followed by complete recovery, severe local pain, self-resolving neck hematoma, skin infections, and mild burns, he noted.
In a series of 16 hyperfunctioning thyroid nodules, multiple PLA treatments induced nearly 60% volume shrinkage but TSH was undetectable in one-third of patients after 6 months (Radiology 2004;232:272-80).
A randomized prospective study compared the efficacy of a single PLA session with one radioiodine treatment in 30 patients with a solitary hot nodule. Both treatments reduced baseline nodule volume by 50%, but after 6 months, normalization of serum TSH was obtained in 50% of patients treated with PLA versus 100% of those treated with radioiodine (Eur. J. Endocrinol. 2007;157:95-100).
Therefore, PLA is not effective for the long-term control of hyperfunctioning thyroid nodules and is not an alternative to 131I therapy. But PLA may be recommended in some cases such as in young patients with incomplete extranodular suppression, or in pregnant women who have an absolute contraindication to radiation therapy, Dr. Papini said.
Radiofrequency ablation (RFA) is an alternative thermoablation technique, in which needle-like electrodes are placed directly into the tumor with the use of US or CT guidance. In a few uncontrolled cases series, RFA produced up to 78% decrease in the size of thyroid nodules. In a large follow-up of 236 patients, the procedure was reported safe and well tolerated, and thyroid nodules and related symptoms appeared stably controlled during a 2-year period (Eur. Radiol. 2008;18:1244-50).
Dr. Papini stated that he had no relevant financial conflicts of interest.
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