World Cancer Day 2017: liver cancer, a global challenge thanks to viruses and alcohol

In part 3 of our World Cancer Day series, we take a look at how liver cancer affects different regions across the world. We’re focusing on cancer that starts in the liver (primary liver cancer), not cancers that begin in other organs and spread to the liver. Take a look at the map below for the global picture of liver cancer rates, and read on to find out what’s causing this variation

Liver cancer isn’t that common in the UK. It accounts for around 2 in every 100 newly diagnosed cancers each year and is the 17th most common type of cancer. But since the late 1970s, liver cancer rates have more than tripled in the UK – a sharp rise compared to other types of cancer.

Globally, however, liver cancer poses an even bigger challenge.

It’s the 6th most common cancer worldwide, approaching 800,000 new cases diagnosed each year, mostly in low-to-middle-income countries.

And if you look at the map above, the regions hardest hit by liver cancer are parts of Asia and Africa.

So what’s behind the rising rates of liver cancer in the UK, and why are rates much higher in Asia and Africa?

Viral hepatitis

There are five main types of hepatitis viruses, A, B, C, D and E. These viruses infect the liver and usually cause inflammation – if the infection isn’t cleared by the immune system (chronic infection) it increases the risk of liver cancer. The 2 most important viruses linked to liver cancer are hepatitis B and C.

Worldwide around 360 million people have chronic hepatitis B infections, and around 150 million chronic hepatitis C.

Dr Tim Harrison , who’s based at UCL and has devoted his research career to studying hepatitis viruses and liver cancer, says it’s through studying the patterns of infection that scientists can begin to understand soaring liver cancer rates.

“Hepatitis B infection is endemic is certain parts of the world, particularly East Asia and parts of Africa. It’s frequently passed between mother and infant, and in some people it becomes a persistent infection,” he says.

Replication of hepatitis B virus in the liver can lead to viral DNA being inserted into the liver cells’ DNA.

“Hepatitis B can lead to liver cancer via different mechanisms,” Harrison says. “In some cases it seems to be linked to long-term inflammation caused by the immune system trying to get rid of the virus. In other cases it seems more likely that the virus has caused a genetic abnormality in our cells that causes them to become cancerous.”

The good news is that a vaccine was developed in 1982, which will protect people from getting infected with the virus.

“Taiwan is a good example of a success story for the vaccine,” says Harrison. “Around 10-12% of people used to carry the infection, but after the vaccine was introduced in 1984 this dropped to less than 1% in the children who were vaccinated.

Dr Tim Harrison

The increase in liver cancers caused by hepatitis C is a consequence of a global pandemic in the second half of the 20th century, according to Harrison.“While liver cancer in children was not common in Taiwan, after the vaccination programme was rolled out the number dropped by almost a half, suggesting the virus was causing some types of childhood liver cancer too. It’s a good indication that in 20 years or so, when liver cancer rates would be peaking for people born in the 80s, we’ll see a big drop in the numbers of liver cancer due to the vaccine.”

This increase stemmed from advances in medicine shortly after the Second World War, which were unknowingly spreading the blood-borne hepatitis C virus. Blood transfusions and poorly sterilised needles used on multiple patients allowed hepatitis C to be transmitted from person to person.

“30 to 40 years later we’re seeing increases in liver cancer thanks to this rise in hepatitis C infection,” says Harrison. “Because acute hepatitis C often doesn’t cause any symptoms, or has mild ‘flu-like’ symptoms, people were unknowingly carrying the virus for many years without it being diagnosed. It wasn’t being picked up until it was too late – they had irreversible liver damage or cancer.”

For many years now, all blood donations are tested for hepatitis C virus (among other diseases) and needles used in healthcare are single-use, dramatically cutting hepatitis C transmission. People who share needles though, for example intravenous drug users, are still at a high risk of contracting the virus.

There’s now a quick and simple blood test doctors can use to diagnose the infection, so people who are at high risk of having the virus can be tested, and treated.

As nationwide vaccination programmes become more common in places with endemic hepatitis B, and measures are in place to prevent, diagnose and treat hepatitis C infection, the number of viral-linked liver cancers will fall in the future. And this’s good news for a cancer than can be prevented.

But it’s not just viruses that can cause liver cancer.

Alcohol and liver cancer

It’s estimated that around a third of liver cancers in developed countries are caused by alcohol.

And looking at global figures, there is a high level of alcohol consumption in developed countries (particularly in Russia and the Eastern bloc). The picture is very different in less developed countries, where drinking levels are low. And a similar pattern is seen in regions where religious beliefs mean people don’t drink.

Professor Linda Bauld, Cancer Research UK’s Chair in Behavioural Research for Cancer Prevention based at the University of Stirling, says that drinking patterns in the UK have changed in the last few decades, and cancer rates may reflect this.

Like smoking and lung cancer, liver cancer caused by alcohol abuse takes many years to develop

– Professor Linda Bauld, Cancer Research UK

“In the UK we’ve actually seen a small decrease in the amount of alcohol people consume on average since 2008. But between 1980 and 2008 sales of alcohol shot up by 42%, and we’re very far from getting back down to pre-1980 levels,” she says.

“And like smoking and lung cancer, liver cancer caused by alcohol abuse takes many years to develop. So we’ve probably not seen the peak of liver cancer rates linked to alcohol yet, and it’s forecast to carry on rising.”

Worrying times ahead

Although there has been a small decrease in alcohol consumption in the UK over the last 10 years, this drop was only seen in certain groups of society, including young people.

“In the UK, just under 5% of the population consume a third of its alcohol, and it’s these very heavy drinkers that are most at risk from liver cancer. We’ve not seen a decrease in the amount of alcohol drunk by this high risk group, unfortunately ,” says Bauld.

While drinking is high in developed countries, levels are at least stable. But in middle-income countries, like China and India, alcohol consumption is sharply rising – probably driven by a flourishing economy, increased alcohol marketing and changing gender roles leading to women drinking more.

Tackling high and rising levels of drinking will be important if we’re going to reduce the number of people with liver cancer in the future. In the UK, independent experts, including some funded by us (such as Professor Bauld), have used the evidence to produce a recommendation for a national strategy to help reduce drinking.

According to Bauld, there are effective ways to tackle drinking both on an individual basis and looking at measures the government can introduce that affect the whole population.

In the UK, just under 5% of the population consume a third of its alcohol.

– Professor Linda Bauld, Cancer Research UK

“Around 9 in 10 people aren’t aware of the link between alcohol and cancer in the UK, so one effective way of reducing alcohol consumption is for GPs or other primary care givers to have a conversation about it and give people advice on ways to change their behaviours around alcohol,” says Bauld. “For example, simply keeping a drinking diary or using an online drink tracker app, can be an eye opener.”

It’s also vital that governments around the world invest in national health campaigns to provide people with clear information about the health risks of drinking alcohol and suggest guidelines for alcohol consumption.

“We also need governments to introduce measures to tackle the price, promotion and availability of alcohol, such as minimum unit pricing,” says Bauld. “Tackling marketing, alcohol content of drinks, and reviewing the number and density of pubs and restaurants could all help reduce the amount people drink.”

Our drinking habits in developed countries, and increasing levels of alcohol consumption in countries with rising income, is bad news for liver cancer rates in the future.

It’s vital that countries with high alcohol consumption take steps to reduce these levels, if we’re to reduce the global burden of liver cancer in the future.

Emma

This is not a complete list of the risk factors that cause liver cancer – for example, smoking also increases your risk of developing the disease (see here for more information). And alcohol is linked to several other types of cancer too. For more information, visit our health pages.