Abstract PS5-04-15: Improving Adrenal Insufficiency Screening in Patient Receiving Keynote-522

Abstract Abstract Title: Improving Adrenal Insufficiency Screening in Patient Receiving Keynote-522 Investigators: Amanda Golden, MD, Katherine Clifton, MD, Mara Hoefherr, PharmD, Huda Al-Bahadili, MD Background: Endocrine toxicities of immune checkpoint inhibitors, such as the pembrolizumab, are well known and documented. Immune-related adverse events from checkpoint inhibitors can present as endocrinopathies involving any organ system. In KEYNOTE-522, 18 patients (2.3%) of any grade and 10 patients (1.3%) with grade 3 adrenal insufficiency (AI) were reported in the pembrolizumab arm. Testing for adrenal insufficiency in this population is imperative as the symptoms of this toxicity can be very vague and nonspecific. Current cortisol testing is recommended by the pembrolizumab package insert, however is not well established in clinical practice. This study investigates improved screening for adrenal insufficiency in KEYNOTE-522 patients. Methods: In this retrospective, single center quality improvement project at baseline, at 8 and at 16 weeks of therapy with the Keynote-522 regimen. Any value greater than 12 is considered normal, 12 or below is considered abnormal and had further testing done. System plans were updated. Patients were included if they received treatment from 3/1/2024 - 9/1/2025. The authors will collect baseline endocrine data, pertinent variables (i.e, symptoms of endocrine disorders, recent steroid use, amount of pembrolizumab received, i.e.), and outcomes. Results: A total of 70 patients were given KEYNOTE-522 in the specified timeframe and had baseline cortisol drawn. We plan to collect baseline endocrine laboratory parameters. We will Strengths include the resources and protocols already in place for patients undergoing the Keynote-522 regimen. We would be able to incorporate the testing for adrenal insufficiency into already planned labs draws. Potential limitations or confounding factors could be if a patient has recently gotten any treatment with dexamethasone or another steroid treatment. This could affect the values listed above. If the data would prove to be inconclusive for a patient, then next steps would be a chart review to ensure they did not have glucocorticoid therapy prior to lab testing. Results will be collected after 9/1/2025 and incorporated into the poster presentation and subsequent manuscript. Citation Format: M. Hofherr, A. Golden, K. Clifton, H. Al-Bahadili. Improving Adrenal Insufficiency Screening in Patient Receiving Keynote-522 [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS5-04-15.