BASELINE TSH LEVEL IS ASSOCIATED WITH RISK OF ANTI-PD-1-INDUCED THYROID DYSFUNCTION.

Objective: To characterize anti-programmed cell death 1 (PD-1)-induced thyroid immune-related adverse events (irAEs) in metastatic melanoma patients treated at our institution and to identify risk factors associated with their development. Methods: We reviewed the files of 154 patients with metastatic melanoma treated with PD-1 inhibitors at a single institution from November 1, 2011, to February 28, 2017. The association of thyroid irAEs within 120 days posttreatment initiation with age, gender, melanoma characteristics, treatment protocol, and baseline thyroid-stimulating hormone (TSH) was examined. Results: Overall, 42.4% developed thyroid dysfunction following treatment, including 20.2% (20/99) subclinical thyroid dysfunction, 13.1% (13/99) overt hypothyroidism, and 9.1% (9/99) overt hyperthyroidism. Of those that developed overt hyperthyroidism, 8 progressed to overt hypothyroidism, consistent with thyroiditis. Age, gender, melanoma characteristics, or treatment protocol did not modify the risk of developing thyroid irAEs. Higher baseline TSH was observed in patients who developed overt hypothyroidism versus hyperthyroidism versus those who remained euthyroid (P = .05). A pretreatment TSH >2.19 mIU/mL was associated with an increased risk of overt thyroid dysfunction (odds ratio, 3.46; 95% confidence interval, 1.2 to 9.8). Conclusion: Thyroid dysfunction following treatment with PD-1 inhibitors is common, and patients with a higher baseline TSH appear to be at increased risk. Such patients may benefit from closer monitoring of their thyroid function following initiation of anti PD-1 agents. Abbreviations: CTLA-4 = cytotoxic T-lymphocyte antigen 4; FT3 = free triiodothyronine; FT4 = free thyroxine; irAE = immune-related adverse event; PD-1 = programmed cell death 1; TFT = thyroid function test; TPO = thyroid peroxidase; TSH = thyroid-stimulating hormone.