S. Taylor2, W. E. Zahnd2, S. Ganai1,2 1Southern Illinois University School Of Medicine,Surgery,Springfield, IL, USA 2Southern Illinois University School Of Medicine,Population Science And Policy,Springfield, IL, USA
Introduction: Hepatocellular carcinoma (HCC) is among the fastest growing causes of cancer mortality in the United States (U.S.). Major modifiable risk factors for HCC include viral hepatitis and excess alcohol consumption, the prevalence of which may vary by region, geography, and race/ethnicity. We hypothesized that differences exist in incidence of HCC between rural and urban U.S. populations, and that these may be reflective of differences in ethnic diversity.
Methods: We analyzed data from the SEER 18 database, a population-based collection of cancer registries representative of the U.S. population, and calculated age-adjusted incidence rates, rate ratios (RR), annual percentage change (APC), and total percentage change (TPC) for HCC. Rural and urban population incidence rates were calculated by race from 2010 to 2014, with analysis of trends from 2000 to 2014.
Results: The overall incidence of HCC was 6.8 (95% CI, 6.8-6.9) per 100,000 in urban population versus 5.1 (95% CI, 6.8-6.9) in rural ones (RR 0.75, 95% CI, 0.72-0.78; p<0.05). The lowest incidence was seen in the White non-Hispanic population (4.6 per 100,000). White Hispanics had the highest incidence of HCC (11.0 per 100,000). The greatest urban-rural difference was seen in the Black population (RR 0.58). Both urban (APC 3.7; 95% CI, 3.1-4.3; TPC 65.6) and rural (APC 5.4, 95% CI; 4.5-6.4; TPC 108.9) populations saw an increasing trend in HCC incidence. Rural non-Hispanic Whites and Blacks had the largest annual increase in incidence at 5.6% (TPC of 106.3 and 163.5, respectively). The urban Asian population was the only group to see a decrease in incidence trend (APC -1.1, TPC -4.6). Rural Asians (TPC 2.6) and rural American Indians (TPC 5.7) had APCs that were not significantly different from zero over the 15-year time period.
Conclusions: Although both urban and rural incidence of HCC is increasing, rural incidence is increasing at an accelerated rate compared to urban, a finding that was unexpected. Despite the relatively high incidence of HCC in Asian-urban populations, it was the only population with a downward trend in incidence rates. Causes of this decrease should be identified and applied more broadly with the goal of decreasing the overall incidence of HCC.