SUN-450 - Clinical Management of Immune Checkpoint Inhibitor-Induced Secondary Adrenal Insufficiency Due to Hypophysitis: A Practice Gap Analysis

Background: Immune checkpoint inhibitors (ICIs) are associated with immune-related adverse events (IrAE), such as ICI-induced hypophysitis (ICI-H). This is often associated with hypothalamic pituitary axis dysfunction, the most serious of which is secondary adrenal insufficiency (SAI) for which patients are routinely screened. In the event of ICI mediated SAI, ASCO recommends endocrinology evaluation, immediate replacement of deficient hormones, and continuation of ICI once stabilized.

Objective: The aim of this study was to identify adherence to ASCO guidance with regards to the continuation of ICIs in the setting of ICI-H with SAI among practitioners at a university hospital.

Methods: This retrospective study included patients within a single health system exposed to ICIs from 2013-2024 who developed SAI. Patients aged ≤17, those with pituitary adenomas, pituitary surgery/radiation, or pre-existing AI were excluded. 33 eligible participants were identified. Data was gathered via chart review by an attending endocrinologist and 2 medical students. The response to ICI-H was categorized as: 1) Followed guidelines: ICI continued despite SAI, 2) Followed guidelines: ICI discontinued for other valid medical reasons, 3) Guidelines not followed: ICI discontinued due to SAI, or 4) Missing Data. It was also noted if endocrinology was consulted and if cortisol was provided before levothyroxine when applicable.

Results: Of the 33 patients included in the study, ICI was continued in 12 patients (36%) after a diagnosis of SAI; discontinued in 16 patients (48%) due to another valid medical reason (such as an already completed treatment course, cure, disease progression on ICI, or grade 4 IrAE of another organ system); and discontinued due to SAI in 4 patients (12%). There was missing data for 1 patient (3%) in which the category was inconclusive. All patients (100%) were referred to endocrinology. 12 patients (36%) had concomitant hypothyroidism. Of these, 7 patients (21% of total cohort) received cortisol replacement before thyroid hormone replacement, and the remaining 5 (15% of total cohort) had pre-existing hypothyroidism for which they were already receiving thyroid hormone replacement before ICI-H induced SAI.

Conclusion: Clinical management of ICI-H induced SAI was largely concordant (85%) with ASCO guidelines. However, this study highlights opportunities for continued education to ensure consistent management with a therapy known to improve cancer outcomes. Endocrinology consultation was universal, and appropriate sequencing of hormone replacement therapy was followed when indicated. Overall, these findings suggest strong adherence to guideline-based care of ICI-H induced SAI in this group of patients.

*Unless otherwise noted, all abstracts presented at ENDO must not be released to the press or the public until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.*