12265 Isolated Adrenocorticotropic Hormone Deficiency In The Setting Of Anti-PD1 Immunotherapy

Abstract Disclosure: J. Poncelet: None. Q. Wang: None. A.J. Montero: Advisory Board Member; Self; AstraZeneca, Gilead. Other; Self; Medical Advisor for Paragon Infusion Services. L. Tranchito: None. Isolated Adrenocorticotropic Hormone Deficiency in the Setting of Anti-PD1 Immunotherapy Introduction: Immune checkpoint inhibitors have been associated with endocrine immune-related adverse events, such as secondary adrenal insufficiency with isolated ACTH deficiency in rare instances. Case Presentations: We present two different cases of isolated ACTH deficiency (IAD) while on anti-PD1 therapy with pembrolizumab. Patient A is a 66-year-old woman with history of tobacco use, hypertension, and COPD diagnosed with stage IV lung adenocarcinoma. After completing 15 cycles of pembrolizumab, she reported symptoms of fatigue, weakness, lightheadedness, and was subsequently admitted to the hospital for symptomatic hyponatremia. Lab workup revealed a morning cortisol level of 0.6 ug/dL (n2.5-20 ug/dL) and ACTH <1.5 pg/mL (n7.2-63.3 pg/mL), both of which had previously been normal. Her TSH was mildly elevated with a normal free T4. Her FSH, LH, prolactin, and IGF levels were normal as was MRI of the pituitary. She therefore was diagnosed with IAD and started physiologic steroid replacement therapy with hydrocortisone with subsequent symptomatic improvement and normalization of her serum sodium. Patient B is a 60-year-old woman with a history of osteoporosis, aortic stenosis, and stage II triple negative breast cancer treated with neoadjuvant chemotherapy and pembrolizumab. Two months after starting immunotherapy, she presented to her oncology office with symptoms of fatigue, poor appetite, body aches, and dizziness. Her labs revealed mild hyponatremia, cortisol of 0.9 ug/dL (n2.5-20 ug/dL) and ACTH <1.5 pg/mL (n7.2-63.3 pg/mL). TSH, LH, FSH, and prolactin levels were normal. She started physiologic steroid replacement therapy with hydrocortisone for IAD, which led to improvement in her symptoms. Both patients continue pembrolizumab. Conclusions: Immune-related adverse events affecting endocrine pathways have been reported with immune checkpoint inhibitors. There is no method to predict which patients may be affected, and no guidelines exist on when or how often to monitor hormone levels in these patients. Importantly, patients can continue immune checkpoint inhibitors despite IAD if controlled by hormone replacement, though ACTH recovery should not be expected[1]. Recognition of symptoms can prompt earlier evaluation for secondary adrenal insufficiency and provide greater benefit to patients. 1.Schneider BJ, Naidoo J, Santomasso BD, et al. Management of Immune-Related Adverse Events in Patients Treated With Immune Checkpoint Inhibitor Therapy: ASCO Guideline Update [published correction appears in J Clin Oncol. 2022 Jan 20;40(3):315]. J Clin Oncol. 2021;39(36):4073-4126. doi:10.1200/JCO.21.01440 Presentation: 6/1/2024