BACKGROUND
Thyroid cancer is being detected in more and more people, but luckily it has an excellent prognosis. Overall, very few patients with thyroid cancer actually die of their cancer. This low death rate, however, does result in many years of follow up visits, labs, and ultrasounds for the patients. Discharging thyroid cancer patients who are low risk of recurrence and many years after their initial thyroidectomy might be beneficial to reduce the financial burden on patients and the patient volume on the hospital systems. During surveillance of thyroid cancer, it can be difficult to differentiate a thyroid cancer recurrence from persistent thyroid cancer that was not completely removed.

The purpose of the study is to identify risk factors and frequency of true recurrences of thyroid cancer in patients whose disease is characterized as low risk of recurrence.

THE FULL ARTICLE TITLE
Pałyga I etg al. The frequency of differentiated thyroid cancer recurrence in 2302 patients with excellent response to primary therapy. J Clin Endocrinol Metab 2024;109(2):e569-e578. doi:10.1210/clinem/dgad571.

SUMMARY OF THE STUDY
A total of 2,302 patients who had low risk of recurrence thyroid cancers with excellent responses to therapy from Holy Cross Cancer Center in Poland were analyzed from 1998 to 2021. As the majority of patients were treated before the latest release of the American Thyroid Association thyroid cancer guidelines in 2015, only patients with a thyroid cancer less than 1 cm underwent a lobectomy. Patients with thyroid cancer above the size of 1 cm had a total thyroidectomy and central neck lymph node dissection, and if spread to the lymph nodes were detected, a lateral lymph node dissection was performed. Although the dose was not specified, all patients with a thyroid cancer measuring greater than 1 cm received radioactive iodine therapy.

Excellent response to therapy was defined by both suppressed (low-normal TSH) and stimulated (intentionally high TSH following thyrogen injections) thyroglobulin levels less than 1 ng/dL. A local structural recurrence was defined a lymph node that was confirmed to contain thyroid cancer cells by biopsy. Distant metastatic spread of cancer to other organs such as the lungs and bones was detected with radioactive iodine whole body scans or FDG PET scans.

Of the thyroid cancers, 94% of the cancers were papillary thyroid cancers, and 67.7% of the cancers measured less than 1 cm. Of the 2,132 patients, only 32 patients (1.4%) had a recurrence of their cancer. The cumulative recurrence rate at 5 years and 24 years after thyroidectomy were 1.2% and 2.9%, respectively. Of the recurrences, 62.5% were within 5 years of the initial thyroidectomy. Risk factors for a recurrence are a younger age, larger cancer size, spread to the lymph nodes, incomplete resection during surgery, and higher risk classification using the American Thyroid Association guidelines.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
This study confirms that the recurrence rate of thyroid cancer in patients who are having an excellent response to therapy is very low. Even patients with low risk of recurrence thyroid cancers according to the American Thyroid Association classification who do not receive radioactive iodine still have low rates of recurrent disease. Patients with smaller thyroid cancers, negative lymph nodes, and a low risk of recurrence per the American Thyroid Association guidelines likely do not need indefinite testing for thyroid cancer for surveillance and can be discharged from cancer follow up. Having confidence that, at some point, a patient can safely be followed symptomatically without surveillance labs or imaging would relieve the burden placed on patients and hospitals. The time point of discharge for these low risk of recurrence thyroid cancer patients who are having an excellent response to therapy is still to be determined, but may be as early as 5 years after surgery.

— Pinar Smith, MD

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