BACKGROUND
Surgery is primary treatment for thyroid cancer. Although the risk is low in hands of an experienced thyroid surgeon, complications such as hypoparathyroidism causing hypocalcemia (low calcium levels) and vocal cord dysfunction causing voice problems can occur. Some patients may not be good candidate for surgery due to other preexisting medical conditions.

Radiofrequency ablation (RFA) is being used for treatment of large thyroid nodules in recent years as an alternative to surgery. RFA delivers high-energy heat via an electrical rod inserted to the thyroid nodule, causing destruction of the tissue and subsequent shrinkage of the nodule. RFA has shown promise as an alternative to surgery for treatment of low-risk papillary thyroid cancer in several studies. However, it is still not clear how to define treatment success and how to select an appropriate papillary thyroid cancer for RFA. This study evaluated long-term findings after RFA treatment of low-risk papillary thyroid cancer.

THE FULL ARTICLE TITLE
Li X et al. Sonographic evolution and pathologic findings of papillary thyroid cancer after radiofrequency ablation: a five-year retrospective cohort study. Thyroid. Epub 2023 Nov 20; doi: 10.1089/thy.2023.0415. PMID: 37885207.

SUMMARY OF THE STUDY
A total of 382 patients (297 females, 85 males, average age of 43 years) were included in this study done in a single hospital in China between May 2014 and August 2021. All patients had stage 1 papillary thyroid cancer, where cancer size was less than 2 cm and there was no metastasis (spread of cancer) to lymph nodes or to other parts of body (distant metastasis). The cancer size was <1cm in 341 patients and 1-2 cm in 41patients. Patients were treated with RFA by an experienced physician with ablation of at least 2 mm outside the original cancer border in an effort to destroy all cancer cells. Patients had biopsy of the area treated to assess for persistent cancer and were followed for an average of 68 months after RFA.

A total of 15 patients (10 patients (2.9%) with cancers <1 cm and 5 patients (12.2%) with cancers 1-2 cm) had persistent cancer after RFA. Among these patients with persistent cancer, 11 underwent repeat RFA with cure and 4 chose observation without repeat RFA and did not have further progression of cancer. One patient developed spread of the cancer to a neck lymph node 21 months after RFA, which was successfully treated with RFA of lymph node. No patients developed spread of the cancer outside the neck. Large cancer size and cancer location close to the thyroid gland border were associated with higher risk of persistent cancer after RFA. Male sex, age < 40 years, cancer <1 cm and higher energy used for RFA were associated with higher likelihood of cancer disappearance.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
This study shows that RFA can be effective in treating low-risk papillary thyroid cancer, although persistent cancer is more common when the cancer size is >1cm. However, there are some practical limitations to make RFA for thyroid cancer a routine practice at this time, including provider expertise and availability of the RFA equipment and higher resolution US machines. Also, the findings of this study suggest that RFA would be a good option for treatment of low-risk papillary thyroid cancer that is smaller than 1cm. The current American Thyroid Association guidelines do not recommend routine biopsy of thyroid nodules less than 1cm to minimize potential impact of unnecessary surgery and subsequent need for surveillance and levothyroxine therapy. These guidelines may change as RFA becomes more widespread. Overall, this study is important to identify another option in the management of thyroid cancer. Larger studies are needed to determine how best to utilize RFA in treatment of low-risk papillary thyroid cancer.

— Sun Y. Lee, MD, MSc

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