This pilot, single-arm clinical study evaluates the feasibility, safety, and effectiveness of radiofrequency ablation (RFA) as a curative treatment for small, low-risk papillary thyroid cancer (PTC). The study will enroll 30 adult patients (≥18 years) with biopsy-confirmed PTC measuring <2 cm, who decline surgery or active surveillance, or who are transitioning from active surveillance to active treatment.

Eligible participants will undergo ultrasound-guided RFA performed with curative intent at University Health Network. Patients will be followed for up to 12 months with scheduled clinical visits, neck ultrasounds, blood tests, voice assessments, and patient-reported outcome questionnaires. A biopsy of the ablation site at 6-12 months will be used to assess local cancer control.

The primary objective is to determine the local cure rate and safety profile of RFA for low-risk PTC. Secondary objectives include evaluating post-ablation ultrasound features, patient-reported quality of life, and the feasibility of implementing a multidisciplinary thyroid RFA program within routine clinical practice.

Results from this study will provide important preliminary data to inform future larger trials comparing RFA with surgery and active surveillance for selected patients with low-risk papillary thyroid cancer.

This study is a pilot clinical trial designed to evaluate a less invasive treatment option for adults with small, low-risk papillary thyroid cancer (PTC). PTC is the most common type of thyroid cancer and is often slow growing with an excellent prognosis. Standard treatment usually involves surgery to remove part or all of the thyroid gland. While surgery is highly effective, it may be associated with complications such as voice changes, low calcium levels, prolonged recovery, and the need for lifelong thyroid hormone replacement. For some patients, close monitoring without treatment (active surveillance) is an option, but this approach can cause ongoing anxiety and uncertainty.

Radiofrequency ablation (RFA) is a minimally invasive, image-guided procedure that uses controlled heat to destroy targeted tissue. RFA has been widely used to treat benign thyroid nodules and is increasingly being explored as a treatment for carefully selected small thyroid cancers. This study aims to determine whether RFA can safely and effectively eliminate small PTCs while preserving the thyroid gland and reducing the impact of treatment on patients' daily lives.

The study will enroll 30 adult participants (18 years or older) with biopsy-confirmed papillary thyroid cancer measuring less than 2 cm, with no evidence of spread outside the thyroid or to lymph nodes. All participants will have previously been offered standard treatment options and have chosen not to undergo surgery or active surveillance, or will be transitioning from active surveillance to active treatment. Each potential participant will be reviewed by a multidisciplinary team that includes radiology, endocrinology, and surgical specialists to ensure the treatment is appropriate and safe.

The RFA procedure will be performed on an outpatient basis under local anesthesia and light sedation, using real-time ultrasound guidance to precisely target the cancer while protecting nearby structures such as the vocal cords, trachea, and esophagus. Patients are typically observed briefly after the procedure and can return home the same day.

Following treatment, participants will be followed closely for up to 12 months. Follow-up includes clinic visits, neck ultrasound examinations, blood tests to assess thyroid function, voice assessments, and questionnaires that evaluate symptoms, quality of life, satisfaction with treatment, and decision-related concerns. A key component of follow-up is an ultrasound-guided biopsy of the treated area performed 6 to 12 months after RFA, which will be used to determine whether the cancer has been successfully eradicated.

The primary focus of the study is to assess local cancer control and safety of RFA, including the frequency and severity of any complications. Additional goals include understanding how treated thyroid cancers appear on ultrasound over time, evaluating patient-reported outcomes, and assessing the practicality of delivering and sustaining a multidisciplinary thyroid RFA program within a Canadian academic health-care setting.

The results of this study will provide important early evidence on the role of radiofrequency ablation as a potential alternative to surgery for selected patients with low-risk papillary thyroid cancer and will help guide future larger clinical trials and treatment guidelines.

Inclusion criteria:

• Histologically confirmed papillary thyroid carcinoma (PTC) by fine-needle aspiration (FNA -Bethesda V/VI ) or core needle biopsy.
• Single or multiple lesions, each 2.0 cm in maximum diameter.
• Intrathyroidal tumors (i.e., no extrathyroidal extension, no clinical/radiological evidence of nodal metastases, nor distant metastases).
• Lesions located at a safe distance (>2 mm) from critical structures (e.g., trachea, esophagus, carotid artery) or accessible with hydrodissection.
• ≤T1b (i.e. < 2cm maximal diameter), N0 or Nx, M0 (no clinical or radiological evidence of lymph node or distant metastasis).
• Patients unfit for surgery due to comorbidities or who refuse surgery.
• ≥18 years old
• Not pregnant at the time of RFA.
• Able to understand and voluntarily sign informed consent.

Exclusion Criteria:

• Evidence of lymph node involvement (clinically or radiologically suspicious or confirmed metastatic nodes) or distant metastasis (e.g., lung, bone).
• Tumors with extrathyroidal extension
• Tumors with extensive calcification
• Tumors located within 2 mm of critical structures where RFA would pose an unacceptably high risk and where hydrodissection is not feasible.
• Previous thyroid surgery or ablation (RFA, ethanol, laser, or microwave) at the index tumor site.
• Known diagnosis of anaplastic, poorly differentiated, or other aggressive thyroid cancer variants.
• Pregnant or breastfeeding at the time of enrollment.
• Bleeding diathesis or use of anticoagulants that cannot be discontinued safely prior to RFA.
• Severe comorbid illness that limits life expectancy to less than 5 years.
• Inability to adhere to study follow-up schedule or procedures or lacking decision-making capacity.
• Implanted electrical devices such as pacemakers or neurostimulators
• Infection in the neck including skin infection or thyroiditis at time of planned ablation.
• Severe cervical anatomy distortion (prior neck surgery or radiation with distorted anatomy that prevents safe RFA

De-identified individual participant data (IPD) from this study may be shared with qualified researchers upon reasonable request. Data sharing will be considered after completion of the primary analyses and publication of the main study results. Shared data will exclude all direct identifiers and will comply with institutional policies, REB requirements, and applicable privacy legislation.

Requests will be reviewed by the study Principal Investigator to ensure scientific validity, ethical appropriateness, and alignment with the original consent. Data will be shared under a data-sharing agreement outlining the permitted use of the data, data security requirements, and restrictions on re-identification or further sharing.

De-identified IPD and supporting documents will be made available after publication of the primary study results or within 12 months of study completion, whichever occurs first.

IPD will be shared upon reasonable request with qualified researchers. Requests must include a brief research proposal and intended use of the data. All requests will be reviewed and approved by the Principal Investigator and must comply with Research Ethics Board (REB) approval, participant consent, and institutional data-sharing policies.

Conditions of use:

Data will be provided in a de-identified format and shared under a formal data-sharing