Climate change may be driving rise in liver cancer: study

GI cancer

By Mardi Chapman

27 Jan 2023

The rapid rise of liver cancer in Australia, mainly in the equatorial and tropical regions and not explained by known risk factors, has researchers questioning a link between liver cancer and climate change.

The research, published in the journal Science of the Total Environment [link here], said recognised risk factors such as viral hepatitis and alcohol consumption are decreasing in contrast to the increasing incidence of liver cancer.

The investigators said the incidence of liver cancer in Australia has increased by 306% and mortality from liver cancer by 184% between 1982 to 2015.

Yet hepatitis B and C infections, the main drivers of liver cancer, have dropped considerably owing to antiviral treatment and prevention strategies which suggests other factors are contributing to the increased liver cancer.

Their research compared the risk of liver cancer with lung cancer in the same regions to control for confounders such as socioeconomic factors of access to health care, income and education.

Lung cancer also has similar risk factors to liver cancer but is on the decline in the same regions.

The research found hot spots for liver cancer in Australia included the Nhulunbuy, East Arnhem and Torres Strait Islands – with more than double the standardised incidence ratio (SIR) of lung cancer.

“The mean temperature anomaly in Australia has shown an upward trend over the past decades, with annual mean temperatures increasing in almost all climate classifications, but the health effects of increased temperatures are likely to be more prominent in hotter regions such as the equatorial and tropical regions because mean temperatures in these regions are significantly higher than in other regions,” the study said.

It said their findings were consistent with other research such as the Cancer Incidence in Five Continents data [link here] which found humid and hot climate conditions were associated with liver cancer incidence.

“Such a result is similar to the distribution of liver cancer we observed in Australia. Moreover, environmental and climate change, including air pollution, precipitation, fungi, and viruses, may bring changes to the maps of cancer and liver diseases.”

Carcinogenic fungus

The study noted the optimal growth temperature for Aspergillus, the fungus that produces the carcinogen aflatoxin, is 25–40 °C which overlaps with the temperature in tropical and subtropical regions. As well there was evidence that the accumulation of aflatoxin was accelerating in hot environments.

“Climate can affect all procedures of crops production, heat and drought can help Aspergillus colonise pre-harvest crops and accelerate the synthesis of aflatoxin, while humid storage conditions can lead to post-harvest contamination,” it said.

The investigators, including Professor Wenbiao Hu, from the Queensland University of Technology’s School of Public Health and Social Work, and Professor Hilary Bambrick, Director of the National Centre for Epidemiology and Population Health, said climate change was also having an impact on the transmission pattern of viruses.

This may in turn affect the trends and distribution of liver cancer which was predominantly a virus-mediated cancer.

They said climate change could also impact rates of obesity and NAFLD, risk factors for liver cancer, through dietary pattern changes.

Another potential factor was the involuntary migration of people from HBV endemic areas in the Asia-Pacific region due to weather-related disasters, which may increase Australia’s apparent liver cancer incidence.

The investigators called for more research including efforts to combine cancer surveillance and environmental surveillance to develop “climate-driven cancer prediction models and provide early warning of liver cancer risk to the public,” they concluded.

Other liver cancer hot spots identified in the study included Sydney which has the highest number of chronic hepatitis B patients in Australia.

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