Immune Checkpoint Inhibitor-induced Thyroid Disorders: A Single Center Experience

Background: Immune checkpoint inhibitors (ICI) foster T lymphocytes to fight cancer, but they can also trigger immune-related adverse events (irAE) in various organs, including thyroid dysfunction that can manifest itself in terms of both hyperthyroidism and hypothyroidism or subclinical disease.

Objective: Based on previous observations, this study evaluated the impact of oncological immunotherapy on the development of thyroid dysfunction in a cohort of patients treated with ICI at our institution.

Methods: We collected 10 cases of thyroid irAE that emerged from 24 cancer patients treated with immunotherapy, belonging to a cohort of 120 patients who were sent to our clinic by the Oncology Department of our institution, between December 2016 and March 2020.

Results: From the analysis of the data, thyroid irAEs emerged after a median time of 9 weeks, and they occurred mainly in females. Regardless of the initial presentation (thyroiditis with thyrotoxicosis, hypothyroidism, or worsening of the previous subclinical hypothyroidism), later all patients developed persistent hypothyroidism which required hormone replacement therapy with levothyroxine. This finding was confirmed by a statistically significant increase in the median value of TSH (thyroid-stimulating hormone) between the pre-ICI treatment and subsequent phases and, for the first time, by a reduction in the median value of the thyroid volume estimated by neck ultrasound, a sign of destructive thyroiditis.

Conclusion: Our results confirm that patients undergoing immunotherapy should be monitored for potential thyroid dysfunction with biochemical assessments and changes in thyroid volume estimated by ultrasound could be helpful in the diagnostic work-up.