e14713 Background: Endocrine irAEs have been reported in association with various ICI and are characterized by their correlation with improved survival outcomes. A growing clinical comprehension of endocrine irAEs has facilitated the development of effective treatment strategies involving hormone replacement, which has been shown to enhance patients' quality of life. This study aims to evaluate outcomes in patients (pts) experiencing endocrine irAEs and identify predictive factors for their occurrence. Methods: This retrospective cohort study comprised 214 adult pts with solid malignant tumors who underwent ICI, either as monotherapy or in combination with other chemotherapeutic agents, at the SBIH Moscow Clinical Scientific and Practical Center named after A.S. Loginov of DHM. Results: Between June 2016 and January 2023, 214 pts were included in the study (46.3% female, 53.7% male). The median age was 62.6 years (range 32–91). At the data cut-off (1 February 2024) the median overall survival (OS) for the analyzed population was 34,5 months (95%CI 21,15-43,91). No significant difference in median OS was observed between pts with overall endocrine irAEs and those exhibiting specific manifestations, such as hypocortisolism and destructive diabetes mellitus. However, thyroid irAEs were associated with improved median OS: 27.5 months compared to 22.6 months in those without (p=0.037); RR=1.39 (95%CI 1.025-1.89; p=0.036). The grade of endocrine irAEs did not impact the survival benefit. A significant association was observed between age group and endocrine irAEs (Pearson’s χ2=9.92, p=0.019), with a left-skewed age distribution due to a higher proportion of participants aged 32–44 years among those developing endocrine irAEs. Pts with nodular goiter had a 2.91 times higher risk of developing thyroiditis (95%CI 1.03–8.25), although this did not reach statistical significance (p=0.067). Calcium channel blockers were associated with an increased risk of developing thyroid irAEs (RR=1.54, 95%CI 1.09–2.19; p=0.036). Antihistamine use was a robust predictor of hypothyroidism with a RR=1.68 (95%CI 1.05–2.7, p=0.04). Initial derived neutrophil-to-lymphocyte ratio (dNLR) ≥3 predict the development of endocrine irAEs (Pearson χ2=4.02; p=0.045) as well as dNLR>2.2 (Pearson χ2=4.22, p=0.04). Conclusions: Thyroid irAEs are correlated with improved OS. Predictors of endocrine irAEs may include young age (32-44 years), calcium channel blocker or antihistamine use, dNLR ≥3, or dNLR >2.2. Prospective trials are warranted to validate these findings.