Cases of primary liver cancer, an often preventable disease, have trebled in the last 30 years, figures suggest.

数据显示，原发性肝癌--一种可以预防的疾病，患病人数在过去30年间翻了三倍。

While it is not uncommon¹ for cancer to spread to the liver, Cancer Research UK statistics show incidents where it starts in the organ have risen sharply.

Cases of cancer overall have increased over recent decades as people live longer and detection methods improve.

But experts say hepatitis C（丙肝） infections, as well as alcohol and obesity²（肥胖，肥大）, have helped fuel the spike³ in liver cases.

Primary tumours⁴ frequently develop as a result of cirrhosis（硬化）, itself associated with these risk factors.

Hepatitis C is a virus spread by blood-to-blood contact. Prior to 1991, transfusions⁵（倾注，渗透，灌输） were the most common source of infection, but since screening was introduced the disease is most commonly spread among intravenous（静脉的，静脉注射的） drug users.

Matt Seymour, professor of gastronintestinal cancer at the University of Leeds, said: "We are seeing more patients with cirrhosis and, in turn, more patients with primary liver cancer.

"This is likely to continue. There is a long delay between exposure to the risk factors and the onset⁶（攻击，进攻） of cancer.

"It might take between 20 and 40 years for liver cancer to develop after infection with hepatitis C. So even if new cases of infection stopped, the number of cases would continue to rise for some years."

Screening call

Obesity is now thought to be one of the most common causes of liver disease, while cases of cirrhosis associated with excessive drinking are known to have soared in the UK in recent years.

Caught early enough, some of the damage caused by liver disease can be reversed（颠倒） and the risk of cancer developing reduced.

But many people with hepatitis C do not know they are carrying the virus: estimates suggest that while more than 250,000 people in the UK have been infected, eight out of 10 are unaware⁷.

The five-year survival rate for primary liver cancer is low, and Cancer Research UK says it is currently supporting a number of trials to improve the treatment of the condition.

Imogen Shillito, of the British Liver Trust, said: "We know liver cancer is caused by years of liver damage, often from infection with hepatitis B or C, or regular excessive drinking.

"But there are many interventions⁸ that can prevent liver cancer. In particular, if people at risk are screened for hepatitis B or C and are offered effective treatment before liver damage has set in, their risk of liver cancer drops dramatically.

"We want to see the NHS diagnosing and treating liver disease at an early stage to prevent liver cancer developing and save lives."