Pre-existing mental health diagnosis and colorectal cancer outcomes.

e15711 Background: Mental health disorders are common among patients (pts) with cancer, sometimes associated with delays in diagnosis and treatment. The impact of pre-existing mental health diagnoses (MHD) on colorectal cancer (CRC) presentation and outcomes is not well understood. Methods: We conducted a retrospective study of pts with MHD and CRC treated between 2015 and 2020 at a comprehensive cancer center. Cox proportional hazards models were used to compare overall survival (OS) among pts diagnosed with an MHD either before or after their CRC diagnosis, followed by sensitivity analysis and propensity score matching (PSM). MHD is defined as anxiety, depression, substance use disorder, PTSD, bipolar disorder, and schizophrenia. OS was defined as the time from CRC diagnosis to death from any cause. Statistical significance was set at 0.05. Results: A total of 528 patients with MHD were included;19.2% had pre-existing MHD (pre-MHD). Compared to patients without pre-MHD, those with pre-MHD were older (≥ 60 years) (69.61% vs 44.84%, p &lt; 0.0001) and less likely to present with advanced (stage IV) disease (19.61% vs 35.45%, p &lt; 0.001). Significant predictors of mortality included Black race (HR = 1.72, 95%CI: 1.32–2.24, p &lt; 0.0001), male sex (HR = 1.35, 95%CI: 1.05–1.74, p = 0.019), and stage IV disease (HR vs stage I = 5.32, 95% CI: 3.47–8.16, p &lt; 0.0001). In the unadjusted Cox proportional hazards analysis, pre-MHD was not associated with OS, but was associated with worse OS in the adjusted model (HR = 1.51, 95% CI: 1.09–2.08, p = 0.012). PSM cohort of 204 patients; The propensity of having a pre-MHD was modeled as a function of age, tumor site, and stage. In the unadjusted analysis, the estimated HR of pre-MHD was 1.51 (95% CI 1.00 - 2.28, p = 0.049). However, this association was attenuated in the adjusted model (HR = 1.50, 95% CI 0.99 – 2.28, p = 0.055). Conclusions: Despite presenting with less advanced disease, patients with pre-MHD experienced worse survival. These findings highlight the importance of integrating mental health assessment and support into oncologic care. Validation in larger, prospective cohorts is needed while targeting high-risk groups for intervention. Patient characteristics stratified by Pre-existing Mental Health Diagnosis. Demographics Total (N=528) Pre-MHD(N=102) No pre-MHD(N=426) P-value Site 0.026 Colon 383(72.54) 83(81.37) 300(70.42) Rectum 145(27.46) 19(18.63) 126(29.58) Stage &lt;0.001 1 86(16.29) 31(30.39) 55(12.91) 2 115(21.78) 20(19.61) 95(22.3) 3 156(29.55) 31(30.39) 125(29.34) 4 171(32.39) 20(19.61) 151(35.45) Sex 0.513 Female 311(58.90) 63(61.76) 248(58.22) Male 217(41.10) 39(38.24) 178(41.78) Age at cancer diagnosis &lt;0.001 Median (IQR) 59(50-69) 68(56-82) <jats:td