Reduced treatment adherence and cancer mortality in patients with depression.

11040 Background: Depression affects up to 20% of cancer patients and is associated with poorer cancer outcomes. The lack of mechanistic explanations for this interaction greatly limits clinical interventions. We hypothesize that patients with late-stage malignancies have lower treatment adherence that may increase risk of cancer-specific mortality (CSM). Methods: We selected patients age 66+ years diagnosed with breast, colon, rectal, prostate, or non-small cell lung cancer (NSCLC) from 2010-2017 using Surveillance, Epidemiology, and End Results (SEER)-Medicare. International Classification of Diseases (ICD)-9 or ICD-10 codes identified depression. Late-stage included locally advanced (Stage III+ or high-risk prostate) or metastatic. Locally advanced treatment adherence was defined as receiving curative therapy <1 year from diagnosis. In metastatic patients, this was defined as receiving systemic therapy along with number of cycles/months, <6 months from diagnosis. Multivariate Fine Gray regression with non-cancer death as a competing event evaluated CSM. Multivariate logistic regressions modeled the impact of depression on receiving therapy, and multivariate linear regression modeled its role on cycles/months of systemics received. Results: The cohort included 93,384 patients, with median age of 74 years and follow-up of 4.2 years. In total, 21,690 patients (23.2%) had depression, highest in NSCLC (27.1%) and lowest in prostate (13.4%). Depression was associated with 6-36% increased risk (p<0.01) of CSM (Table 1). Locally advanced patients with depression had 15-32% lower odds (p<0.01) of receiving curative treatment. Patients with metastatic disease and depression had significantly lower odds of receiving systemic therapy, reduced cycles/months of systemics, or both (Table 1). Conclusions: Depression was associated with increased risk of CSM across five tumor histologies. Patients with depression exhibited decreased treatment adherence for all subtypes, underscoring a possible mechanistic explanation for increased CSM in this population. Multivariate regressions for depression effect. Endpoint CSM:SHR 95% CI, p Received treatment:Locally advancedOR 95% CI, p Received treatment:MetastaticOR 95% CI, p Therapy cycles/months:Metastatic,B Coefficient, p Histology Breast 1.11 1.02-1.24, <0.01 0.78 0.65-0.92, <0.01 0.85 0.71-1.03, 0.10 -0.52, <0.01 Colon 1.15 1.10-1.20, <0.01 0.71 0.63-0.79, <0.01 0.67 0.59-0.75, <0.01 -0.63, <0.01 Rectal 1.13 1.02-1.25, <0.01 0.68 0.53-0.87, <0.01 0.67 0.52-0.88, <0.01 -0.24, 0.33 Prostate 1.36 1.25-1.48, <0.01 0.85 0.78-0.93, <0.01 0.94 0.69-1.31, 0.71 -0.22, 0.02 NSCLC 1.06 1.04-1.09, <0.01 0.75 0.67-0.84, <0.01 0.94 0.88-0.999, 0.045 -0.21, <0.01 SHR: Subdistribution hazard radio; OR: odds ratio; CI: confidence interval.