FRI539 Vitamin D and Endocrine Immune-Related Adverse Events in Patients Treated with Immune Checkpoint Inhibitors

Disclosure: Z. He: None. A. Leiter: None. E. Carroll: None. G. Santiago Pichardo: None. I. Khanna: None. E. Gutowski: None. E.J. Gallagher: Research Investigator; Self; Novartis Pharmaceuticals, Flare Therapeutics, Seagen. Background: Low vitamin D levels have been previously associated with the development of thyroid dysfunction in non-cancer populations. Thyroid dysfunction is one of the most common immune-related adverse events (irAEs) induced by immune checkpoint inhibitors (ICIs). Currently, the effect of vitamin D deficiency or vitamin D supplementation on the development of ICI-induced thyroid dysfunction is unknown. This study was design to examine the association between baseline vitamin D levels and vitamin D supplementation, and the development of ICI-induced thyroid dysfunction. Methods: In this IRB-approved, retrospective cohort study, we collected demographic and clinical characteristics in addition to TSH, free T4, and vitamin D levels from patients with melanoma, multiple myeloma (MM), and transitional cell carcinoma (TCC) treated with ICIs between 2011 and 2020, in a large urban hospital system. The primary outcome was the occurrence of thyroid dysfunction defined by abnormal TSH or free T4 level after ICI initiation. Vitamin D deficiency / insufficiency was defined as serum 25-hydroxy-vitamin D level