Racial disparities in conditional survival of oral cavity squamous cell carcinoma: a surveillance, epidemiology, and end results-based analysis

Purpose To examine racial disparities in conditional survival (CS) among patients with oral cavity squamous cell carcinoma (OSCC). While racial differences in incidence, stage at diagnosis, and overall survival are well established, it is unclear whether these disparities persist or diminish over time among patients who survive beyond diagnosis. CS offers a dynamic prognostic estimate that may better characterize the attenuation of survival gaps over time. Methods Using the Surveillance, Epidemiology, and End Results (SEER) database, we conducted a population-based retrospective analysis of 24,632 individuals diagnosed with OSCC between 2004–2015. Five-year cancer-specific CS was calculated using the Kaplan–Meier method. Multivariable time-varying Cox regression was performed to obtain hazard ratios (HRs) of 5-year mortality by race, adjusting for age, socioeconomic demographics, tumor grade and stage, subsite, and treatment modality. Results Of patients analyzed, 85.6% were White, 6.7% Black, and 7.7% Asian/Pacific Islander (API). Initial 5-year CS revealed marked disparities: Black patients (43.4%) had substantially lower survival than White (62.1%) and API (63.0%) patients. By year 5 post-treatment, survival differences narrowed considerably (Black: 84.3%, White: 87.7%, API: 89.3%). Black patients faced elevated mortality risk early (Year 1 HR: 1.21, 95% CI: 1.10–1.33, P < 0.001), which was no longer statistically significant among long-term survivors (Year 5 HR: 1.05, 95% CI: 0.84–1.32, P = 0.642; n = 90 events among 553 Black patients at risk). API patients showed consistently comparable outcomes to White patients across all time points. Conclusion OSCC racial survival disparities follow a convergence trajectory, with excess mortality risk concentrated within the first three post-treatment years. This pattern implicates early-phase factors as drivers of disparity.