RFA Treatment for Papillary Thyroid Microcarcinoma

Differentiated thyroid cancer (DTC), which includes papillary and follicular cancer, comprises the vast majority (\>90%) of all thyroid cancers. The yearly incidence has nearly tripled from 4.9 per 100,000 in 1975 to 14.3 per 100,000 in 2009. Almost the entire change has been attributed to an increase in the incidence of papillary thyroid cancer (PTC). This increase in incidence is likely driven by the diagnosis of small PTCs \<1cm in size due to the increasing use of neck ultrasonography. In a study observing 1235 patients with small papillary thyroid cancer over 22 years, it was noted that at 10 years follow-up, only 8% had tumor enlargement of \>3mm and 3.8% had novel lymph node metastases proving that the majority of these 'microcarcinomas' were low-risk and indolent in nature. In 2017, the US commissioned task force evaluating the risks and benefits of treatment of these small cancers concluded that surgical treatment of these microcarcinomas was associated with a low, but not negligible, risk of surgical complications: 2.12-5.93% risk of permanent hypoparathyroidism and 0.99-2.13% risk of permanent recurrent laryngeal nerve injury. In addition, 98.8% of patients treated with thyroidectomy received radioactive iodine that was associated with an excess absolute risk of 11.9 to 13.3 cancers per 10, 000 person-years for second malignancies. In accordance with these data, the most recent societal guidelines for management of thyroid nodules and differentiated thyroid cancer have favored less aggressive management of microcarcinomas, with active surveillance as a reasonable option for management. However, although this may appeal to a subset of individuals who are especially risk and surgery averse, many patients are still uncomfortable with observing 'cancer' and still opt for the least invasive approach to surgical treatment. Thyroid surgery has always been the mainstay of treatment for thyroid cancer. Although associated with excellent outcomes in experienced hands, thyroid surgery carries a low risk of complications that include recurrent or superior laryngeal nerve injury leading to voice changes, hypoparathyroidism, hypothyroidism with need for thyroid hormone supplementation, and unsightly scarring. Although many patients with thyroid cancer find these risks acceptable, these risks are sometimes less acceptable to patients with benign disease. In an era when the medical field is treating thyroid diseases less aggressively, there is a pressing need to identify approaches to treat indolent malignant disease less invasively. Introduced in the early 2000s, ultrasound-guided percutaneous ablation of thyroid lesions has emerged as a potential alternative to surgery in patients with benign thyroid nodules. Of the myriad ablation methods, the most commonly used technique is radiofrequency ablation (RFA). An expanding body of evidence shows that radiofrequency ablation and other percutaneous interventions are effective treatments for benign solid thyroid nodules, toxic adenomas, and thyroid cysts resulting in overall volume reduction ranges of 40-70% with durable resolution of compressive and hyperthyroid symptoms. In addition, RFA has been used as an effective alternative treatment in the management of locally recurrent thyroid cancers in patients who are not good surgical candidates. In addition, RFA of other solid tumors is a commonly performed procedure in the United states and all RFA devices, including the device the investigators will use for the clinical care of these patients, are cleared by the FDA (New devices/technology to the market are approved, but devices that have a predicate device/technology that are already on the market only need to be cleared). Recently, a systematic review and meta-analysis of thermal ablation techniques for micropapillary carcinomas found that among 503 low risk PTCs in 470 patients, no patient experienced tumor recurrence or distant metastasis, 2 patients (0.4%) experienced lymph node metastasis, 1 patient (0.2%) developed a new PTMC, which was successfully treated by additional ablation, and 5 patients (1.1%) underwent delayed surgery after ablation, including the two patients with lymph node metastasis and three additional patients with unknown etiology. Although these percutaneous techniques have been steadily gaining acceptance in Europe and Asia over the past 20 years, they have been slow to be adopted in the US. There remains a dearth of data regarding clinical experience in the United States and no randomized clinical trials have been performed evaluating RFA vs active surveillance for micropapillary carcinomas.

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