Quantifying the Role of Stage-at-Diagnosis in Racial Disparities in US Cancer Survival: A Population-Based SEER Study for 8 Common Cancers

Background Black patients with cancer experience worse relative survival, yet it remains unclear how far shifting diagnoses towards earlier stage would reduce mortality. Methods We analysed Surveillance, Epidemiology, and End Results (SEER) data (2004–2022) for U.S. Black and White patients aged 15–89 years with eight common cancers, using a 2021–2022 period-analysis window. We estimated age-standardised survival under observed and counterfactual stage distributions in which Black patients had the White stage distribution. We quantified the proportion of the racial survival gap mediated by stage and deaths postponed beyond specified follow-up times. Results Among 1,299,386 eligible patients, Black patients were diagnosed at similar or younger ages and had more distant-stage disease for most sites, except rectal cancer in Black women aged < 75 years. At 5 years, stage accounted for large shares of the Black-White disparity in breast, colon, corpus uteri, lung, and oral cavity and pharynx cancers. The mediated proportion was low for rectal cancer in men, pancreatic cancer, and ovarian cancer, with weak evidence for ovarian cancer at age 75 + years and pancreatic cancer in women. The negative indirect effect for rectal cancer in younger women indicated suppression. Deaths postponed varied by follow-up time and cohort size. Conclusions Stage equalisation could yield meaningful short-term mortality reductions for several sites, but stage-focused strategies are not universally beneficial. Equity-oriented policies should pair earlier diagnosis with interventions to improve downstream care pathways.