To compare the clinical outcomes of Thermal ablation with those of thyroid lobectomy in patients with subcapsular papillary thyroid microcarcinoma.

The global incidence of papillary thyroid microcarcinoma (PTMC) has increased rapidly in recent decades because of improved ultrasound (US) detection and fine needle aspiration biopsy and has primarily contributed to the surge in cases of thyroid carcinoma. Given the indolent characteristics of most PTMCs, the American Thyroid Association guidelines recommend active surveillance for low-risk PTMC to prevent over-treatment. Nevertheless, in many countries, active surveillance poses challenges, including patient anxiety, limited medical resources, and insurance coverage limitations when adopted. Furthermore, many patients prefer treatment rather than active surveillance due to anxiety, a meta-analysis showed that a significant proportion of patients (8.7%-32%) who underwent delayed surgery without tumor progression during active surveillance. Thyroid lobectomy (TL), replacing total thyroidectomy is recommended as the first-line treatment for PTMC by several guidelines. However, there were still concerns remain regarding lifelong hormone replacement therapy, surgery-related complications, and the potential over-treatment associated with TL.

Thermal ablation (TA) has emerged as a viable alternative for the managing of PTMC within the thyroid gland, as evidenced by studies conducted across various Asian and European countries. It has been endorsed as an alternative treatment strategy to TL in clinical guidelines issued by multiple professional associations in Europe, Asia, and North America. However, controversy persists regarding its usefulness for subcapsular PTMC because of concerns about potential extrathyroidal extension (ETE) or occult lymph node metastasis (LNM), which may impact disease progression post-treatment. There are also technical challenges and safety issues when ablating subcapsular lesions. To date, a limited number of studies have reported the short-term efficacy of TA in treating subcapsular PTMC.However, these studies were constrained by small sample sizes and the absence of comparative analyses between the first-line treatment option, TL, and TA. Consequently, further research is needed to fully understand the role of TA in the therapeutic management of subcapsular PTMC and its potential as an alternative to TL.

Therefore, the aim of this multicenter study was to compare the clinical outcomes of TA with those of TL in patients with subcapsular PTMC.

Inclusion Criteria:

1. a unifocal papillary thyroid carcinoma (PTC) diagnosed by fine-needle aspiration or core-needle biopsy;
2. tumor with a maximum diameter of ≤ 10 mm detected on ultrasound;
3. tumor located within ≤ 2mm from the thyroid capsule (with or without tumor-associated capsular bulging or capsular discontinuity);
4. absence of clinical or imaging evidence of gross ETE (involvement of strap muscles, obtuse angles between the tumor and trachea/esophagus, protrusion into the tracheoesophageal groove, and invasion into other neck structures);
5. no clinical or imaging evidence suggesting lymph node metastasis or distant metastasis

Exclusion Criteria:

1. aggressive subtypes of PTC (aggressive subtypes of PTC includes the tall cell, columnar cell, solid, and hobnail variants);
2. multifocal PTMC;
3. history of neck surgery or TA;
4. a follow-up period of < 24 months;
5. incomplete follow-up data, or poor-quality pre-treatment ultrasound images

This study included patients with clinical T1aN0M0 PTC who underwent thermal ablation or thyroid lobectomy at three institutions between June 2014 and December 2020.

Some of the data generated or analyzed during the study are available from the corresponding author by reasonable request.