The short answer
Much of Japan's liver cancer has been linked to long-term hepatitis B and C infection. Vaccines and antiviral treatment have helped lower this risk. Alcohol and fatty liver disease also matter. For people at higher risk, regular liver checks can catch cancer early.
Long-term hepatitis B and C infection has been a major cause of liver cancer in Japan.
Hepatitis B vaccination and antiviral treatment can lower liver cancer risk.
Heavy alcohol use and fatty liver disease also raise the risk.
People at higher risk may be offered regular liver checks to catch cancer early.
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The full explanation.
Reading level: written for a 6th–8th grade reading level. Short sections, plain words, no jargon.
The simple answer
Liver cancer in Japan is closely tied to long-term viral hepatitis — mainly hepatitis B and C — which slowly damages the liver over many years. Alcohol and fatty liver disease add to the risk. The hopeful part is that vaccines, antiviral treatments, and healthy habits can prevent much of this damage, and regular checks can catch cancer early in people at higher risk.
Hepatitis: the leading cause
For decades, a large share of Japan's liver cancer has been linked to chronic infection with hepatitis B or hepatitis C. These viruses can live in the liver for years, quietly causing inflammation and scarring. Over time, this damage can lead to cirrhosis and then to liver cancer.
Hepatitis C, in particular, drove much of Japan's liver cancer in the past. Many people were infected years ago and did not know it, because the virus often causes no symptoms until serious damage has occurred.
Progress through vaccines and antivirals
This is a story with real hope, because we have tools that work.
A vaccine protects against hepatitis B. Widespread vaccination, especially of infants, prevents new infections and, over time, lowers liver cancer rates.
Antiviral medicines have transformed care. Treatments can control hepatitis B and cure most cases of hepatitis C. By calming or clearing the infection, they reduce liver damage and lower the risk of liver cancer. As more people in Japan have been tested and treated, hepatitis-related liver cancer has been declining.
The lesson is powerful: when a cancer has an infectious cause, preventing or treating that infection can prevent cancer.
Alcohol and fatty liver
Not all liver cancer comes from hepatitis. Heavy alcohol use damages the liver and raises cancer risk, especially when combined with viral hepatitis. And as excess weight becomes more common, fatty liver disease — a buildup of fat in the liver — is a growing cause of liver damage worldwide, including in Japan.
These causes are important because they are becoming more common even as hepatitis declines. Limiting alcohol and managing weight and related conditions can help protect the liver.
Catching it early
For people who already have long-term liver disease or hepatitis, doctors often recommend regular liver checks — usually ultrasound scans and blood tests — to look for cancer early. Because these people are at higher risk, this monitoring can find liver cancer when it is smaller and more treatable.
This is a form of targeted screening: not for everyone, but for those whose risk is known to be higher.
A changing mix of causes
Liver cancer offers a striking example of how a disease's causes can shift over time. In Japan, hepatitis C once drove the large majority of cases. Thanks to testing, antiviral cures, and vaccination against hepatitis B, that share has been falling. But as one cause fades, others are growing — especially fatty liver disease linked to excess weight and metabolic conditions, and alcohol-related liver damage. This means prevention has to keep evolving. Clearing hepatitis is a huge win, but protecting the liver now also means addressing weight, blood sugar, and alcohol. The overall lesson is hopeful: liver cancer has many preventable causes, and progress on one front is real, even as new challenges appear.
What this means for you
Two simple questions are worth asking your doctor: Should I be tested for hepatitis B or C? And do I need the hepatitis B vaccine? Many infections go unnoticed, and testing can open the door to treatment that protects your liver.
If you have liver disease or a hepatitis infection, ask whether regular liver checks are right for you. And for everyone, limiting alcohol and keeping a healthy weight support liver health. These steps will not remove all risk, but they meaningfully shift the odds.
Sources to verify before publishing
- National Cancer Institute, liver cancer: https://www.cancer.gov/types/liver
- National Cancer Center Japan, liver cancer statistics: https://ganjoho.jp/reg_stat/statistics/en/
- CDC, viral hepatitis: https://www.cdc.gov/hepatitis/
- World Health Organization, hepatitis: https://www.who.int/health-topics/hepatitis
Before you go
This article is for education only and is not a substitute for medical advice. Talk with a healthcare professional about your personal cancer risk, symptoms, screening, or treatment options.
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Common questions
▸What causes most liver cancer in Japan?
Much of Japan's liver cancer has been linked to long-term infection with hepatitis B or C viruses, which slowly damage the liver over years. Alcohol and fatty liver disease are other important causes.
▸Can liver cancer be prevented?
Many cases can be reduced. Hepatitis B vaccination prevents that infection, and antiviral medicines can treat hepatitis B and C, lowering liver damage and cancer risk. Limiting alcohol and managing fatty liver also help.
▸How is liver cancer caught early?
People with long-term liver disease or hepatitis may be offered regular checks, such as ultrasound scans and blood tests, to catch cancer early when it is more treatable.
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