Disparities in Timeliness of Cancer Diagnosis Across a Multi-Site Academic Health System.

Background: Early cancer diagnosis improves survival and quality of life, yet disparities in stage at diagnosis persist. This study evaluates demographic, clinical, insurance, and neighborhood-level socioeconomic factors associated with late-stage cancer diagnosis within an academic health system. Methods: We conducted a retrospective cohort study of 27,064 adults diagnosed with breast, colorectal, or lung and bronchus cancer between 2015 and 2025 in the University of California Health System. Late-stage disease was defined as AJCC stage III/IV. Multivariable logistic regression examined associations between late-stage diagnosis and patient characteristics, insurance status, comorbidity burden, and neighborhood socioeconomic measures, including the Area Deprivation Index (ADI), Social Vulnerability Index (SVI), and Healthy Places Index (HPI). Results: 17.6% of patients were diagnosed at a late stage. Cancer type was the strongest predictor, with lung (aOR ≈ 13-14) and colorectal cancer (aOR ≈ 8) associated with higher odds of late-stage diagnosis compared with breast cancer. Residence in medium and high ADI tertiles and Medicaid insurance (OR = 1.16; 95% CI: 1.06-1.28) were associated with higher odds of late-stage diagnosis, while Veterans Affairs coverage was associated with lower odds (OR = 0.76; 95% CI: 0.58-1.01). SVI was not associated with stage at diagnosis, whereas higher HPI scores were modestly protective. Conclusion: Late-stage cancer diagnosis is driven primarily by cancer type and insurance status, with additional contributions from neighborhood disadvantage.