The results, according to one of the study’s authors, indicate that liver cancer is an underrecognized and deadly cancer that is increasingly affecting people living in rural areas of the United States.
The incidence of hepatocellular carcinoma — the most common form of liver cancer — has decreased in urban areas but steadily increased in rural areas of the United States over the past two decades, according to recently published data.
The results — which were printed in the journal Cancer — show a widening disparity between the two patient populations and emphasize the need for further research on what is driving this increase, according to the study authors.
Lead study author Dr. Kali Zhou, an assistant professor of clinical medicine at the Keck School of Medicine of the University of Southern California, said in an interview with CURE® that this study focused primarily on the rates of liver cancer because of its poorer prognosis compared to other cancers.
“It’s really important we raise awareness because, first and foremost, prevention followed by early diagnosis are crucial to identifying the cancer early and saving lives,” she mentioned.
The study results demonstrated that out of 310,635 cases of hepatocellular carcinoma diagnosed from 1995 to 2015, 85% were among people who resided in urban areas and 15% were among those who lived in rural areas. The higher incidence of hepatocellular carcinoma in urban settings, according to Zhou, stems from a higher frequency of people having certain chronic liver diseases, including viral hepatitis.
Although the study results demonstrated that most cases of hepatocellular carcinoma occurred in individuals who lived in urban areas, further analysis showed the incidence was slowing down in those communities.
However, the data indicated that there was a 5.7% annual increase in incidence of the disease among people who lived in rural areas. This trend, according to the results, suggests that even though rural areas tend to experience a significantly lower rate of hepatocellular carcinoma incidence, rates of disease are approaching that of urban areas.
Zhou said that she and her colleagues hypothesized that this annual increase may come from increased obesity rates and alcohol use among people who live in rural areas. She added that the Centers for Disease Control and Prevention has reported that obesity is more common in rural areas, and further explained that obesity is associated with an increased risk of liver cancer.
“It’s also possible that due to challenges in accessing health care in rural areas, in particular specialty care, fewer patients with hepatitis C are getting treated or being treated before they develop cirrhosis (chronic liver damage) as compared to urban areas,” she mentioned.
Reasons for Incidence Decline in Urban Areas
The data showed that some urban subgroups started experiencing a decline in hepatocellular carcinoma incidence starting in 2013 and 2014. This decline occurred in men, women, younger people (ages 40-59), Asian Pacific Islander individuals and residents living in the western region of the U.S.
Zhou explained that this decline may be associated with the advances and improvements that have been made in the screening and treatment of chronic viral hepatitis B and C.
“Certain demographics, such as Asians, are more likely to have hepatitis B and much more likely to live in urban areas,” she said. “Thus, improvements in this group likely contributed to declines in urban areas.”
On the other hand, no subgroups residing in rural areas experienced a decline in incidence during the nearly two-decade study period. Instead, hepatocellular carcinoma incidence continued to rapidly increase in men, people aged 60-69 years, non-Hispanic Black individuals, American Indian/Alaskan Native individuals, southern regions of the United States and areas with high census poverty.
During the overall study period, age-adjusted incidence rates of hepatocellular carcinoma were lower in rural areas compared with urban areas.
However, throughout the study period, age-adjusted incidence rates changed substantially by race and ethnicity. Hispanic individuals living in rural areas had a higher age-adjusted incidence rate of hepatocellular carcinoma compared to their counterparts living in urban areas. The greatest incidence over the 20-year period occurred in America Indian/Alaskan Native individuals living in urban areas, and American Indian/Alaskan Native individuals living in rural areas.
More Research is Needed
Zhou explained that it is important to continue to study health outcomes among residents of rural and urban areas. She said that because of the many differences in cancer risk factors and the frequency of medical conditions among residents of rural and urban areas, cancer rates must be studied separately. Moreover, Zhou noted that there are “clear differences” in the health care systems found in urban areas. For instance, residents of rural areas may have less access to valuable resources.
“The disparity in health outcomes, particularly for liver cancer, between rural and urban areas is not well studied,” she concluded. “The importance of this study is to bring greater awareness of liver cancer as an underrecognized and deadly cancer that is increasingly affecting people living in rural areas.”
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