Racial disparities in conditional survival among patients with oral cavity squamous cell carcinoma: A surveillance, epidemiology, and end results-based analysis

Background: Oral cavity squamous cell carcinoma (OCSCC) accounts for a substantial proportion of head and neck cancer-related morbidity and mortality in the United States. Persistent racial disparities in incidence, stage at diagnosis, access to surgical care, and overall survival have been well documented. Traditional survival estimates, however, do not reflect how prognosis evolves after patients survive the initial years following diagnosis. Conditional survival (CS) offers a dynamic estimate of prognosis over time and may better characterize the attenuation of racial survival gaps. Methods: Using the SEER database, we conducted a population-based retrospective analysis of 24632 individuals diagnosed with OCSCC between 2004-2015. 5-year cancer-specific CS was calculated using the Kaplan-Meier method. Information including race, age, various socioeconomic demographics, tumor grade and stage, subsite, and treatment modality was used to perform multivariable Cox regression analysis and obtain hazard ratios (HRs) of 5-year mortality for race. All analyses were conducted using R (version 4.5.1). Results: Of the OCSCC patients analyzed, 80.6% were White, 8.7% Black, and 10.7% Asian/Pacific Islander (API). Initial 5-year CS revealed marked disparities: Black patients (43.2%) had substantially lower survival than White (62.4%) and API patients (63.1%). However, conditional survival demonstrated a dynamic convergence pattern. By year 5 post-treatment, survivors showed narrowed differences: Black patients reached 84.7%, White patients 87.8%, and API patients 88.9% 5-year conditional survival. Time-varying multivariable Cox regression revealed evolving mortality patterns. Black patients faced increased death risk early (Year 0 HR: 1.15, 95% CI: 1.06-1.24; Year 1 HR: 1.22, 95% CI: 1.09-1.36), but this excess risk disappeared among long-term survivors (Year 4 HR: 1.05, P = 0.651; Year 5 HR: 1.08, P = 0.589). API patients consistently showed comparable outcomes to White patients across all timepoints (HRs: 0.87-1.02, all P > 0.05). Conclusion: OCSCC racial survival disparities follow a convergence trajectory. While Black patients experience significantly worse outcomes initially, this gap contracts to just 3 percentage points among 5-year survivors, accompanied by complete resolution of excess mortality risk in adjusted models. This temporal concentration of disparities within the first three post-treatment years may implicate early-phase factors in treatment (e.g., diagnostic delays, treatment barriers) as drivers in early mortality. There was no statistically significant difference in API compared to White patients.