Impact of tumor subsite on survival outcomes in oral squamous cell carcinoma: A retrospective cohort study from 2000 to 2019

Background: Oral squamous cell carcinoma (OSCC) is responsible for high morbidity and mortality worldwide. Although the oral cavity encompasses different anatomical subsites, it is unclear whether subsite localization of carcinoma influences outcome. Methods: This retrospective cohort study examined overall survival (OS), recurrence-free survival (RFS) and local recurrence-free survival (L-RFS) at different subsites by Kaplan-Meier survival curves. Cox proportional hazards regression analysis was performed to investigate the impact of subsite on overall death, locoregional recurrence, and local recurrence. Results: The cohort included 1702 patients treated with curative intent for OSCC according to standardized national guidelines. The 5-year OS was superior in oral tongue to retromolar trigone as well as in both oral tongue and floor-of-mouth (FOM) compared to tumors involving multiple locations. The 3-year RFS in oral tongue and FOM was superior to tumors involving multiple locations, and in FOM compared to retromolar trigone. The 3-year L-RFS in oral tongue and FOM was higher than gingiva, retromolar trigone and tumors involving multiple locations. Adjusting for relevant covariables using oral tongue as reference, tumors involving multiple locations was the only category presenting higher risk for locoregional recurrence, while risk of local recurrence was higher in gingiva, retromolar trigone, hard palate and to tumors involving multiple locations. The study found no difference in risk of death between subsites. Conclusion: The study found differences in survival outcomes between subsites. After adjusting for covariables, subsite mainly had significant impact on local recurrence, with no distinct pattern of influence on overall death or locoregional recurrence.