The incidence of liver cancer has increased over the past 25 years in much of the world, but the cause of that cancer varies greatly depending on the geographic region and, to a certain extent, also varies according to income. These are the conclusions from the Global Burden of Disease (GBD) 2015 study, which was published online October 5 in JAMA Oncology.
"Liver cancer remains a major public health burden globally," senior author, Christina Fitzmaurice, MD, MPH, University of Washington, Seattle, and colleagues write.
"Liver cancer was the fourth leading cause of cancer death in 2015 after lung, colorectal, and stomach cancer," the authors report. In actual numbers, a total of 854,000 incident liver cancer cases occurred around the world in 2015, along with 810,000 deaths.
This added up to 20,578,000 disability-adjusted life-years (DALYs) around the world. As the authors explain, 1 DALY represents 1 lost year of healthy life.
The report also notes that between 1990 and 2015, liver cancer incident cases increased by 75%.
In addition, "[b]etween 1990 and 2015, cases of liver cancer, deaths, and DALYs increased for all cause groups globally. The highest increase in incident cases was due to HCV [hepatitis C virus], followed by alcohol," the investigators observe.
"The highest burden of liver cancer incident cases, deaths, and DALYs was observed in East Asia," they report.
Analysis of only high-income countries in the Asia Pacific revealed that Japan had 75% of incident liver cancer cases, two thirds of which were caused by HCV infection.
Between 1990 and 2015, age-standardized incidence rates of liver cancer also showed that incidence rates increased by over 100% in many high-income countries, including the United States, Canada, Australia, New Zealand, and most European countries.
On the other hand, age-standardized mortality rates (ASMRs) declined substantially in regions such as East Asia and western sub-Saharan Africa, where liver cancer rates have traditionally been high.
For example, ASMRs in China dropped by one third between 1990 and 2015, possibly because of reduced exposure to aflatoxins and to some extent national hepatitis B virus (HBV) vaccination programs. Aflatoxins are a family of toxins produced by certain fungi that are found on agricultural crops, such as maize (corn), peanuts, cottonseed, and tree nuts.
"Marked differences at the global level exist by sex for HBV-related and alcohol-related liver cancer," the investigators continue. For example, HBV caused 203,000 liver cancer cases in men in 2015 but far less than half that number, at 70,000 cases, in women.
Alcohol in turn caused almost the same number of liver cancers in men, at 204,000, in the same year but even fewer than HBV infection caused in women, at only 45,000 cases, again in 2015.
"The contribution of different etiologies to total liver cancer deaths varies markedly between countries and regions," the researchers write.
Overall, HBV and alcohol were the most common causes of death from liver cancer in 2015, causing 33% and 30%, respectively, of global mortality from the disease.
HCV infection caused 21% of liver cancer deaths in the same year, while 16% of deaths were from other causes.
However, the cause of death from liver cancer varied significantly across different geographic regions.
For example, HBV infection was least likely to cause death from liver cancer in places such as southern Latin America and most likely to cause death in western Saharan Africa and in Andean Latin America.
HCV infection in turn was the least common cause of death from liver cancer in East Asia but the most common cause of death from liver cancer in high-income countries in the Asia Pacific region.
Alcohol, perhaps not surprisingly, made the smallest contribution to death from liver cancer in North Africa and the Middle East but was the greatest contributor to liver cancer death in Eastern Europe, where it caused over half of all deaths from the disease in 2015.
Alcohol was also the biggest player behind mortality from liver cancer in Belarus.
"Our results show that most cases of liver cancer can be prevented through vaccination, antiviral treatment, safe blood transfusion and injection practices, as well as interventions to reduce excessive alcohol use," the researchers state.
The fact that liver cancer caused by HBV would have decreased had the population remained the same between 1990 and 2015 suggests that global vaccination against HBV infection is starting to be successful.
Indeed, "assuming that present HBV vaccination trends continue, between 2020 and 2050, the number of new HBV infection is estimated to drop by 70%," the study authors suggest.
The overall increase in incidence rates of liver cancer caused by HCV infection also highlights the importance of both prevention and the need to make HCV antiviral medications more affordable to control the infection when present.
Dr Fitzmaurice has disclosed no relevant financial relationships. Disclosures of other coinvestigators are listed in the publication.
JAMA Oncol. Published online October 5, 2017. Full text
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