BACKGROUND
Thyroid cancer is one of the fastest rising cancers in the world. Part of this increase is due to the detection of thyroid nodules on imaging studies done for another reason. Many of the cancers identified are small and may never cause significant problems. However, other lines of evidence support a true increase in papillary thyroid cancer (the most common type of thyroid cancer) that have more advanced-stage disease at diagnosis, and higher associated death rate. It is projected that by 2040, thyroid cancer will be one of the top four cancer diagnoses, along with breast, colorectal, and kidney and pelvis cancers. Overall, the prognosis of thyroid cancer is excellent, with surgery often the only treatment needed. However, it is unclear for the need for surgery in some patients with small thyroid cancers that are at very low risk of spreading outside of the thyroid. Indeed, some patients with small thyroid cancers are watched without surgery (active surveillance).

The objective of this study was to determine the mode of detection for thyroid nodules that subsequently led to thyroid surgery in varying parts of the world. The goal is to determine whether there was a true increase in papillary thyroid cancer or if this trend is secondary to an increase in nodule detection.

THE FULL ARTICLE TITLE
Sajisevi M et al 2022 Evaluating the rising incidence of thyroid cancer and thyroid nodule detection modes: A multinational, multi-institutional analysis. JAMA Otolaryngol Head Neck Surg 148:811–818. PMID: 35834240.

SUMMARY OF THE STUDY
This is a study of patients who underwent thyroid surgery in 2019 at 16 centers in four different countries. From survey responses provided by investigators at each of the centers, patients were classified into groups by the mode of thyroid detection that led to surgery.

The authors found that of the 1328 patients (average age 52 years, 75% women) included in this study, 41% of patients were asymptomatic at the time of detection, 34% had symptoms related to the thyroid nodule, 14% had other endocrine conditions, and 12% were under surveillance (nodules with original mode of detection unknown). Mode of detection within the asymptomatic category included 20% noted on imaging studies done of other reasons, 1% by patient-requested screening, and 13% by clinician screening examination. CT scan of the chest was the most common imaging test that led to the discovery of thyroid nodules, comprising 31% of the imaging studies done for other reasons.

Thyroid surgery was more often performed in the US and Canada for asymptomatic nodules. Denmark and South Africa had the highest rates of nodules discovered secondary to patient symptoms. The surgical thyroid pathology revealed cancer in 613 cases (46%). Of these patients, only 30% had been symptomatic, thus would not have necessarily come to attention otherwise. The average size of the cancer was larger in symptomatic patients compared to those who were asymptomatic (3.2cm vs 2.1cm).

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
Overall, this study shows that there are differences in the mode of detection of thyroid nodules, and associated surgical practices, from the four countries (Denmark, South Africa, United States, and Canada) whose clinicians were surveyed in this study. Most patients in this study had no thyroid-related symptoms and 60% of those with thyroid cancer fell into this group. The asymptomatic patients had smaller-sized cancers than patients with symptoms, but the average size was still >2 cm. This suggests that there has been an actual increase in thyroid cancer across the world.

— Alan P. Farwell, MD

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