FRI233 Adrenal Insufficiency Due To An Unusual Culprit

Abstract Disclosure: S. Decamps: None. K.T. Yeung: None. K. McCowen: None. Background: Chronic exogenous use of glucocorticoids is the most common cause of reversible secondary adrenal insufficiency (AI). There is a significant risk of cortisol deficiency if the medication is abruptly discontinued. Chronic glucocorticoid therapy may cause hypothalamic-pituitary-adrenal (HPA) axis suppression, resulting in low ACTH, atrophy of the adrenal zona fasciculata and decreased cortisol production. Immunotherapy rarely causes reversible central AI, usually permanent. We present a case of an immunotherapy-receiving patient who presented with biochemical evidence of adrenal insufficiency after using an oral solution (swish and spit) of dexamethasone as prophylaxis for mucositis. Patient Summary: A 52-year-old woman with stage IIb triple negative breast cancer receiving neoadjuvant Datopotamab, Dertuxtecan and Durvalumab was evaluated for adrenal insufficiency. Prior to starting therapy, serum cortisol level measured 7.9 mcg/dL at 11 AM (normal 6.0-18.4 mcg/dL at 6-10 A.M). She had received a single dose of dexamethasone 10 mg IV with her first cycle, but not thereafter. As part of the immunotherapy protocol, serial cortisol levels were obtained, and 2 weeks after the baseline, noon serum cortisol was 1.0 ug/dL. Patient was asymptomatic. At no point were glucocorticoids replaced, but 1-week later serum cortisol level was 0.6ug/dL at 11:00 AM along with an ACTH of 5 pg/mL. Immunotherapy-induced AI was strongly suspected. Her only glucocorticoid exposure had been a dexamethasone oral mouth rinse (swish 10mL for 1 minute and spit out, four times daily). Cortisol level at 7AM a week later measured 3.5 mcg/dL with ACTH 18.7 pg/mL and a dexamethasone level 108.2 ng/dL (normal < 50 ng/dL for patients not on dexamethasone). Technique of swish and spit was reviewed with the patient, and she was not ingesting the medication. An observational approach was pursued at this time given hemodynamic stability, treatment was continued and several weeks later repeat labs showed cortisol levels of 3.3 (7AM), with a dexamethasone level of 84.3 ng/dL. Her course of therapy has been completed, so she has been off the dexamethasone solution, continues to be asymptomatic and repeat labs now show a 9AM Cortisol level of 9.5 mcg/dL and, given lack of other sources, it is most likely that these low cortisol levels along with elevated dexamethasone levels are related to the use of dexamethasone swish and spit rather than immunotherapy induced permanent HPA axis suppression. Conclusion: There is no literature on dexamethasone swish and spit being absorbed systemically possibly leading to potentially reversible HPA suppression. Our case will raise awareness of help guide clinicians expand their differential when working up these patients. Presentation: Friday, June 16, 2023