BACKGROUND
Small thyroid cancers are low risk in terms of the risk for recurrence and spread beyond the thyroid gland. Further, they do not appear to affect survival. In recent years, following small thyroid cancers with physical exam and ultrasound imaging over time without surgery, known as active surveillance, has been proposed as an alternative management option for these small, low risk thyroid cancers. However, the success of active surveillance depends on the selection of appropriate patients. For example, patients whose cancer is close to or invading important structures such as the windpipe (trachea) or the nerve supplying the voice box (recurrent laryngeal nerve) are not suitable candidates for active surveillance.

This study aimed to better understand the significance of the location of the cancer within the thyroid gland and minimum cancer size when selecting patients for active surveillance.

THE FULL ARTICLE TITLE
Newman SK et al 2022 Invasion of a recurrent laryngeal nerve from small well-differentiated papillary thyroid cancers: Patient selection implications for active surveillance. Thyroid 32:164–169. PMID: 34714169.

SUMMARY OF THE STUDY
This was a study of 30 patients with papillary thyroid cancers 2 cm or smaller who had evidence of invasion of the recurrent laryngeal nerve found before or during surgery and who were seen at Memorial Sloan Kettering between 1986 and 2015. Reports of the operative procedure, ultrasound and other imaging techniques was studied in detail. The spread of the cancer beyond the thyroid gland and it’s association with the size of the initial cancer was done as part of the study. Nerve involvement by the thyroid cancer of a nerve called the recurrent laryngeal nerve in the neck was also studied.

The majority of patients were women (76.6%) and the average age at diagnosis was 51.3 years. The average cancer size was 1.6 cm and two-thirds of the cancers with recurrent laryngeal nerve invasion were 1.5-2.0 cm. In addition to the invasion of the recurrent laryngeal nerve, invasion into the trachea, esophagus, fibroadipose tissue, strap muscles, and larynx was seen in 15 (50%), 12 (40%), 4 (13.3%), 3 (10.0%), and 3 (10%) patients, respectively. Imaging before surgery showed invasion of the recurrent laryngeal nerve in only 8 patients (26.7%). In 29 out of 30 patients, the primary cancer was on the inner side of the thyroid next to the trachea. However, the overall risk of involvement of structures in the neck beyond the thyroid gland with these cancers was low. This was especially true for tumors that were very small, that is less than 9 mm in size.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
This study showed that patients with thyroid cancers that are next to the trachea are not appropriate candidates for active surveillance. Moreover, only one-fourth of the patients had findings on imaging before surgery suggesting extension of the cancer beyond the capsule and invading other structures. It is encouraging that invasion of the recurrent laryngeal nerve was not observed for cancers smaller than 0.9 cm regardless of cancer location.

These findings are important to guide physicians and patients when discussing different management options for small thyroid cancers, including active surveillance. In addition to the cancer size and growth rate, the cancer’s location in respect to the trachea and the recurrent laryngeal nerve should be considered in decision-making. It is also important for patients to have high-quality imaging and an experienced multidisciplinary team to carefully interpret findings, before considering active surveillance.

— Maria Papaleontiou, MD and Vibhavasu Sharma, MD, FACE

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