People infected with the hepatitis C virus risk developing liver cancer, and now Japanese researchers have identified several factors that increase that risk.

Being male, advancing age, high liver enzyme levels and low cholesterol levels all increase the likelihood of liver cancer occurring in someone with hepatis C but no current symptoms, they report.

While hepatitis C viral infection is a known risk factor for liver cancer, Dr. Hideo Tanaka of the Osaka Medical Center for Cancer and Cardiovascular Diseases and colleagues note that it is unclear what percentage of people with asymptomatic infection will go on to develop cancer.

To investigate, the researchers looked at a group of individuals 40 years or older who donated blood between 1991 and 1993, some of whom were found to have HCV infection.

For the study, published in the International Journal of Cancer, some 1950 individuals with hepatitis C were compared with a control group of about 150,000 people without hepatitis. The subjects were followed for an average of 99 months.

Among men with hepatitis, the risk of developing liver cancer during follow-up was 22 percent, while the risk for women was 9 percent.

Liver cancer risk increased in tandem with rising liver enzyme levels, and also increased as cholesterol levels dropped. Cancer risk increased with age among both men and women.

The findings underscore the importance of developing effective hepatitis C screening programs in countries where the infection is widespread, the researchers conclude.

SOURCE: International Journal of Cancer, December 20, 2004.