Temporal trends and disparities in oral cavity and oropharyngeal squamous cell carcinoma incidence in Saudi Arabia, 2000-2019: a nationwide population-based study

Oral cavity squamous cell carcinoma (OC-SCC) and oropharyngeal squamous cell carcinoma (OP-SCC) are major contributors to the global burden of head and neck cancer. This study aimed to evaluate nationwide temporal incidence trends in OC-SCC and OP-SCC in Saudi Arabia between 2000 and 2019, stratified by sex, nationality, region of residence, age group, and stage at diagnosis. A nationwide population-based observational study was conducted using data from the Saudi Cancer Registry (SCR) (2000-2019). Age-standardized and age-specific incidence rates were calculated. Temporal trends with annual percent change (APC) and average annual percent change (AAPC) were estimated using the Joinpoint Regression Program. A total of 4,185 SCC cases were included, comprising 3,727 (89.1%) OC-SCC and 458 (10.9%) OP-SCC cases. Most patients were aged 45-74 years (64.7%); 57.7% were male, and 74.5% were Saudi nationals. Overall incidence remained stable throughout the study period for both OC-SCC (AAPC = - 0.60%) and OP-SCC (AAPC = - 0.57%). Age-specific analyses demonstrated a significant increase in OC-SCC incidence among individuals aged < 45 years (APC = + 2.92%; 95% CI, 1.38 to 4.95), whereas it declined among those aged 45-74 years (AAPC = - 3.15%). However, the absolute incidence remained low, and this finding should be interpreted cautiously given the relatively small annual case counts. OP-SCC incidence declined significantly among males (AAPC = - 3.91%) and non-Saudi residents (AAPC = - 7.92%). The Southern region consistently recorded the highest OC-SCC incidence rates, peaking at 2.92 per 100,000 person-years in 2005. Regional trend analyses were limited by insufficient annual case counts in some regions. The proportion of localized disease increased from 35.6% to 46.9% for OC-SCC and from 18.1% to 35.9% for OP-SCC between 2000-2009 and 2010-2019. Early-stage OC-SCC incidence increased significantly during the study period (APC = + 2.40%). Although national incidence rates of OC-SCC and OP-SCC remained stable in Saudi Arabia between 2000 and 2019, important demographic and geographic disparities were observed. The increasing incidence of OC-SCC among younger adults, persistently elevated incidence rates in the Southern region, and the increase in the proportion and incidence of recorded localized-stage disease, accompanied by a reduction in unknown-stage classification, highlight areas for future prevention, surveillance, and etiologic research.