Mapping the Hidden Terrain of Hepatocellular Carcinoma: Exploring Regional Differences in Incidence and Mortality across Two Decades by Using the Largest US Datasets

<b>Background:</b> There is an observed variation in the burden of hepatocellular carcinoma (HCC) across different US populations. Our study aims to comprehensively assess variations in HCC incidence and mortality rates across different regions of the US. Understanding these geographical differences is crucial, given prior evidence indicating variations in the incidence of viral hepatitis and metabolic dysfunction-associated steatotic liver disease and varying access to curative HCC treatment among states. <b>Methods:</b> HCC age-adjusted incidence rates between 2001 and 2021 were obtained from the United States Cancer Statistics (USCS) database (which covers approximately 98% of the US population). HCC age-adjusted mortality rates between 2000 and 2022 were obtained from the National Center of Health Statistics (NCHS) database (covering approximately 100% of the US population). The rates were categorized by US geographical region into West, Midwest, Northeast, and South. Incidence rates were also categorized by race/ethnicity. Time trends [annual percentage change (APC) and average APC (AAPC)] were estimated by using Joinpoint Regression via the weighted Bayesian Information Criteria (<i>p</i> < 0.05). <b>Results:</b> Between 2001 and 2021, there were 491,039 patients diagnosed with HCC in the US (74.2% males). The highest incidence rate per 100,000 population was noted in the West (7.38), followed by the South (6.85). Overall incidence rates increased between 2001 and 2015 and then significantly decreased until 2021 (APC = -2.29). Most cases were in the South (38.8%), which also had the greatest increase in incidence (AAPC = 2.74). All four geographical regions exhibited an overall similar trend with an increase in incidence over the first 10-15 years followed by stable or decreasing rates. While stratification of the trends by race/ethnicity showed slight variations among the regions and groups, the findings are largely similar to all race/ethnic groups combined. Between 2000 and 2022, there were 370,450 patients whose death was attributed to HCC in the US (71.6% males). The highest mortality rate per 100,000 population was noted in the South (5.02), followed by the West (4.99). Overall mortality rates significantly increased between 2000 and 2013 (APC = 1.90), then stabilized between 2013 and 2016, and then significantly decreased till 2022 (APC = -1.59). Most deaths occurred in the South (35.8%), which also had the greatest increase in mortality (AAPC = 1.33). All four geographical regions followed an overall similar trend, with an increase in mortality over the first 10-15 years, followed by stable or decreasing rates. <b>Conclusions:</b> Our analysis, capturing about 98% of the US population, demonstrates an increase in HCC incidence and mortality rates in all geographical regions from 2000 to around 2014-2016, followed by stabilizing and decreasing incidence and mortality rates. We observed regional variations, with the highest incidence and mortality rates noted in the West and South regions and the fastest increase in both incidence and mortality noted in the South. Our findings are likely attributable to the introduction of antiviral therapy. Furthermore, demographic, socioeconomic, and comorbid variability across geographical regions in the US might also play a role in the observed trends. We provide important epidemiologic data for HCC in the US, prompting further studies to investigate the underlying factors responsible for the observed regional variations in HCC incidence and mortality.