Immune Checkpoint Inhibitor-related New-onset Thyroid Dysfunction: A Retrospective Analysis Using the US FDA Adverse Event Reporting System

Objectives The study aimed to investigate the prevalence and demographic characteristics of an immune checkpoint inhibitor (ICI)-related thyroid dysfunction (ICI-TD), and to explore risk factors of poor clinical outcome using data from the US Food and Drug Administration (FDA) Adverse Event Reporting System (FAERS). Methods This is a retrospective study. All cases, aged over 18-year olds, of new-onset or new-diagnosed thyroid dysfunction related to FDA-approved ICIs from January 1, 2011 to December 31, 2020 were identified using FAERS. Data of age, gender, other combined endocrinopathies related to ICIs besides ICI-TDs, and the prognosis was analyzed. Results In total, 2.60% (2971/114 121) cases of ICI-TDs were identified. Among them, 1842 (62.0%) developed hypothyroidism, 675 (22.7%) were hyperthyroidism, and 454 (15.3%) presented in thyroiditis without the mention of thyroid function. Patients on anti- programmed cell death protein-1 (PD-1) therapy displayed higher risk of hypothyroidism compared with other 3 regimens, respectively (P < .01 for all). The likelihood of other immune-related endocrinopathies in patients on the combination therapy of anti-cytotoxic T-cell-associated protein-4 (CTLA-4) and anti-PD-1 was significantly elevated than anti-PD-1 (odds ratio [OR] 2.362, 95% confidence interval [CI] [1.925-2.898], P < .001) and anti-programmed death-ligand 1 (PD-L1) regimens (OR 4.857, 95%CI [3.228-7.308], P < .001). The risk of severe cases was positively related to hypothyroidism in individuals on anti-PD-1 therapy (OR 1.587, 95%CI [1.146-2.197], P = .005) and those on anti-CTLA-4 therapy (OR 3.616, 95%CI [1.285-10.171], P = .015). The risk of severe cases was positively associated with the comorbidity with other endocrinopathies (anti-PD-1 group, OR 0.285, 95%CI [0.200-0.467], P < .001; anti-PD-1+anti-CTLA-4 group, OR 0.574, 95%CI [0.371-0.890], P = .013). Conclusions Regular monitor of thyroid function is indispensable, since ICI-TDs manifested as hypothyroidism or hyperthyroidism, especially those on the combination therapy. Awareness among health care professionals is critical when hypothyroidism occurs, which might indicate poor clinical outcomes.