SUN-072 The Role of Late-Night Salivary Cortisol in Evaluating Endocrine Remission in Patients With Cushing’s Disease Following Pituitary Radiotherapy: A Retrospective Cohort Analysis

Abstract Disclosure: U. Habib: None. H. Shih: None. B.M. Biller: None. N.A. Tritos: None. Pituitary radiotherapy (RT) is an established treatment for persistent or recurrent Cushing’s disease (CD) when transsphenoidal surgery fails to achieve lasting remission. Late-night salivary cortisol (LNSC), a minimally invasive and convenient biomarker, has proven accurate in diagnosing CD. However, its utility in monitoring endocrine remission post-RT remains underexplored, particularly compared to the accepted standard of 24-hour urinary free cortisol (UFC). Understanding the comparative effectiveness of these approaches will be valuable for optimizing long-term disease management.This study aimed to assess the clinical outcomes and utility of LNSC versus UFC in monitoring for endocrine remission in patients with CD following RT. Specific objectives included evaluating remission rates, cardiometabolic outcomes, recurrence risk, and practical implications for patient care.A retrospective cohort study was conducted at a tertiary academic medical center, analyzing 75 patients diagnosed with CD (aged 16–86 years, 71% female) who underwent RT for CD between 2008 and 2023. Patients were categorized into two groups: those monitored using LNSC (group 1, n=16) and those monitored using UFC (group 2, n=18). Forty-one patients who did not achieve remission served as a control group. Key variables included changes in BMI, blood pressure, HbA1c, time to remission, and recurrence rate.Of the 75 patients, 34 (45.3%) achieved endocrine remission during a median follow-up of 56 months. Among these, 16 (21.3%) were monitored using LNSC, and 18 (24%) using UFC. Significant clinical improvements compared to baseline were observed in both groups, including reductions in BMI from baseline (group 1: -3.9 ± 0.7 kg/m², p=0.0001; group 2: -5.2 ± 1.9 kg/m², p=0.0123) and systolic blood pressure (group 1: -7.9 ± 3.9 mm Hg, p=0.03; group 2: -10.1 ± 4.5 mm Hg, p=0.008). The median time to remission was similar between the groups (group 1: 48 months; group 2: 56 months, p=0.76). Both groups demonstrated equivalence in recurrence risk (group 1: 6%; group 2: 11%; p=0.61), and there were no between-group differences in cardiometabolic parameters, including BMI, HbA1c and the number of antihypertensive medications at remission.Our study findings demonstrate that LNSC is accurate in monitoring for endocrine remission after radiation therapy in patients with CD. Patients monitored with LNSC experience comparable clinical and biochemical outcomes at remission; however, LNSC offers practical advantages, including ease of specimen collection and possibly improved patient adherence. These findings suggest that LNSC can be incorporated into routine follow-up protocols for patients with typical sleep-wake cycles who underwent RT. Presentation: Sunday, July 13, 2025