BACKGROUND
Thyroid cancer has been one of the fastest rising cancers until the number of cases started to level off in the past few years. A big part in the increased number of cancers has been the identification of small (<1 cm) cancers. The management of these small cancers is controversial, as many of them may never grow or spread outside the neck. Because of this, it has become increasingly common to follow these small cancers with ultrasound monitoring and hold off on surgery until the cancer starts to grow. This is called active surveillance and is currently accepted as an alternative to surgery for patients with these small thyroid cancers.

The medical community is eager to establish criteria that are predictive of either cancer stability or progression to determine the best candidates for active surveillance. Some predictors of progression are an age <30, elevated TSH, male sex and cancer size more or equal to 0.6 cm. This study was performed to determine if additional characteristics noted on ultrasound may predict progression of small thyroid cancers that would lead to surgery.

THE FULL ARTICLE TITLE
Lee JY et al. US predictors of papillary thyroid microcarcinoma progression at active surveillance. Radiology 2023;309(1):e230006; doi: 10.1148/radiol.230006. PMID: 37906009.

SUMMARY OF THE STUDY
This was a Multicenter study performed at three large hospitals in Korea of 699 participants with Small Thyroid Cancer (≤1 cm). The average age of participants was 50 years and 76% were female. Ultrasounds were performed every 6 months for 2 years, subsequently yearly thereafter for an additional 3 years. The images were evaluated to determine the presence of diffuse thyroid disease (alternatively described as thyroiditis or the appearance of generalized inflammation of the gland), cancer size/ location, brightness, borders, internal blood flow and other characteristics.

Cancer progression was seen in 68 of 699 (~10%) participants, of which 56 (82%) developed cancer enlargement, 3 (4%) developed extension of the cancer outside of the thyroid and 8 (12%) developed spread to the lymph nodes in the neck. No one developed spread of the cancer outside of the neck or died during active surveillance. Patients with diffuse thyroid disease were more than twice as likely to have cancer progression and those with blood flow within the cancer were >1.5 times more likely to progress. The 5-year estimated progression rate was 10.7% if neither diffuse thyroid disease nor blood flow was present, 19.4% if blood flow only was present, 21.7% if diffuse thyroid disease was present, and 23.5% if both diffuse thyroid disease and blood flow was present. The average time to progression was 27.8 months if neither diffuse thyroid disease nor blood flow was present, 20.4 months if blood flow was present, 21.6 months if diffuse thyroid disease was present was present, and 16.4 months if both diffuse thyroid disease and blood flow was present.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
This study shows that active surveillance of small (<1 cm) thyroid cancers is safe, as no patient developed spread of the cancer outside of the neck or death during the monitoring period. This study also shows that ultrasound features can be identified to indicate probability of cancer progression and this may important to aid in decision making regarding active surveillance vs surgery for small thyroid cancers <1 cm. However, the majority of patients (around 80%) of patients who had these findings (diffuse thyroid disease or increased cancer blood flow), did not progress, so these cannot be used as the ultimate factors to decide whether surgery is needed or not. It is possible that a longer follow up would clarify the role of these ultrasound characteristics.

— Maria Brito, MD, ECNU

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