178P Real world diagnosis of immune checkpoint inhibitor induced adrenal insufficiency with 9 a.m. cortisol and the short synacthen test

Results: Of the 198 patients, 66 received definitive immunotherapy and 132 patients received prolonged immunotherapy.The groups were well-balanced across race, insurance status, social vulnerability index, histology, and ECOG.Overall survival did not differ between the two groups as 94 (71.2%) patients in the prolonged and 46 (69.7%) patients in the definitive group were alive at 5 years (p=0.457).The most common reason for discontinuation in the definitive group was end of planned therapy (54.7%) followed by progression of disease (26.6%), then toxicity without progression (12.5%).Conclusions: Maintenance immunotherapy duration has not been clearly defined and is extremely practice-dependent.Stopping immunotherapy at two years has benefits in terms of biologic and financial toxicity but also risks the chance of recurrence and can lead to patient anxiety.Our data supports previous studies demonstrating that there is no survival benefit to continuing immunotherapy past two years of therapy.