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HCC Incidence Gains in US Slowed in Urban But Not Rural Areas.
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AASLD The Liver Meeting Digital Experience, November 13-16, 2020
Mark Mascolini
Incidence (new diagnoses) of hepatocellular carcinoma (HCC) began slowing in 2009 in the United States-but only in urban areas [1]. In rural parts of the country, HCC incidence continues climbing unabated, according to an analysis of the North American Association of Central Cancer Registries (NAACCR). In 2013 Hispanics pulled ahead of Asian-Pacific Islanders and took the lead in HCC incidence figured by US racial/ethnic group.
University of Southern California (USC) researchers who conducted this study reminded colleagues that HCC ranks as the fastest-growing cancer in the United States. Because HCC risk factors may differ between rural and urban areas of the country, the USC team analyzed potential disparities in rural versus urban HCC incidence, which had not been previously studied.
The analysis focused on 1995-2016 data from NAACCR, which collects and certifies all central cancer registry data in the US and Canada, covers 93% of the population, and provides a rural-urban variable. The investigators used USDA Rural-Urban Continuum Codes to classify counties as urban or rural. They calculated three major outcomes:
AAIR, age-adjusted incidence rate for HCC per 100,000 persons
APC, annual percentage change in HCC incidence over a single linear segment
AAPC, average annual percentage change in HCC incidence over the entire study period
The USC team counted 310,635 incident (newly diagnosed) HCC cases from 1995 through 2016, including 85% in urban areas and 15% in rural regions. Non-Hispanic whites made up 82% of the rural population, with non-Hispanic blacks accounting for 8%, Hispanics for 8%, and Asian-Pacific Islanders for 2%. Respective proportions in urban areas were 57%, 16%, 17%, and 10%.
From 1995 to 2009, urban HCC incidence rose smartly at an APC of +5.34%. But that strong upswing in urban incidence slowed in 2009-2014 to +2.71% then started falling in 2014-2016 at an APC of -2.66% (a nonsignificant trend). But in rural regions, HCC incidence showed no signs of slowing throughout the study period, rising 5.70% every year.
AAIR analysis determined the rural HCC incidence rocketed by 218% from 1995 to 2016, compared with an urban incidence gain of 118% over that period. Charting AAIR over those years showed a growing gap between rural and urban HCC incidence.
Asian-Pacific Islanders had the highest age-adjusted HCC incidence through 2013. But they were also the only racial/ethnic group with an overall drop in incidence figured by AAPC for the years 1995-2016 (-1.02%). In 2013 Hispanics surpassed Asian-Pacific Islanders for the highest age-adjusted HCC incidence, and they stayed on top through 2016. Throughout 1995-2016, non-Hispanic whites had the lowest AAIR of any racial/ethnic group analyzed.
In 1995-2016, urban non-Hispanic blacks had the greatest single surge in HCC incidence, as their AAPC vaulted 6.55% between 1999 and 2009. But that change among urban blacks slowed to 2.76% in 2009-2013 then fell by 1.94% in 2013-2016. Over the entire 1995-2016 period, urban blacks had a 1.6-fold greater HCC incidence than rural blacks, 10.0 versus 6.2 per 100,000. But HCC incidence among rural blacks rose steadily over 1995-2016 at an AAPC of 5.38%.
By race/ethnicity and gender, for the whole 20-year study period age-adjusted urban HCC incidence was highest in Asian-Pacific Islander men followed by Hispanic men. For rural areas HCC incidence leaders for 1995-2016 were Hispanic men followed by Asian-Pacific Islander men.
The USC team underlined the "striking rural-urban disparities" they uncovered in HCC incidence trends over the past 2 decades. They stressed that those disparities are growing with time and called for more research on risk factors underlying these disparities. The researchers believe interventions to prevent HCC will have to be tailored to rural populations.
Reference
1. Gainey C, Zhou K, Terrault N. Striking rural-urban disparities in hepatocellular carcinoma trends in the United States, 1995-2016. AASLD The Liver Meeting Digital Experience, November 13-16, 2020. Abstract 136.
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