LAUSR

131Background: Oncological immune checkpoint inhibitors (CPI) commonly cause immune related adverse events (irAEs). Thyroid irAEs have a significant clinical impact requiring therapeutic intervention and clinical coordination whilst often causing treatment delays. Methods: Retrospective review of all patients treated with CPIs (pembrolizumab, nivolumab +/- ipilimumab) for metastatic melanoma at the Clatterbridge Cancer Centre, UK identified patients experiencing thyroid irAEs. Clinical/biochemical course (T4 and thyroid stimulating hormone (TSH) levels) and autoantibody titers were evaluated to identify characterisable trajectories. Results: From February 2016 to May 2017, 103 patients received anti-PD1 therapy; 90 receiving monotherapy and 13 combination. Thyroid irAEs were seen in 13(14.4%) and 3(23%) patients respectively. Two distinct trajectories were identified: a hyperthyroid phase with subsequent hypothyroidism (HH) and de novo hypothyroidism (DN). There were no outliers. HH was the predominant pa...