Increasing incidence and improving survival of oral tongue squamous cell carcinoma

We evaluated changes in incidence, relative survival (RS), and conditional survival (CS) of head and neck squamous cell carcinoma (HNSCC), focusing on oral tongue squamous cell carcinoma (OTSCC). Data of 74 680 HNSCC patients from 1976 to 2015 were obtained from the Surveillance, Epidemiology, and End Results database. Five anatomical sites and their subsites were analyzed. Annual percent change (APC) of incidence was calculated. RS and CS were compared across the four decades. Adjusted hazard ratios (aHRs) of RS were evaluated using multivariate regression. OTSCC incidence decreased from 1976 (APC = -0.76, P < 0.05) but has increased since 1999 (APC = 2.36, P < 0.05). During 2006-2015, the 5-year CS exceeded 90% only for OTSCC and oropharyngeal squamous cell carcinoma (OPSCC). RS improved in OTSCC (aHR = 0.697, 95% confidence interval [CI] 0.642-0.757, P < 0.001) and OPSCC (aHR = 0.669, 95% CI 0.633-0.706, P < 0.001) during the last two decades. For both OTSCC and OPSCC, improved survival was observed regardless of treatment. Incidence and survival remained unchanged for nasopharyngeal, hypopharyngeal, and laryngeal cancers during this period. In conclusion, OTSCC incidence has been increasing since the 2000s, with improving prognosis irrespective of treatment. Given its similarity to OPSCC, OTSCC may represent an emerging HNSCC, warranting further research and clinical recognition.