There are many medical risks seemingly unquestioned by doctors and patients alike. Most people know, for example, that hypertension significantly increases the chance of developing coronary disease--in fact, it doubles the odds.

But other, less well-known risks may exist, some just as dangerous.

Take the claim by one Harvard researcher who says that the odds of developing primary liver-cell cancer, one of the world's five most deadly forms of the disease, may be twenty-five times as high in a person who tests positive for the Hepatitis C virus as in those that don't.

According to Associate Clinical Professor of Medicine Dr. Robert H. Resnick '52, 40 percent of the 1,930 patients in his first-ever worldwide study of Hepatitis C individuals diagnosed with liver cancer tested positive for the Hepatitis C virus.

Resnick published his data earlier this year in the American Medical Association's Archives of Internal Medicine.

While it has long been known that the Hepatitis B virus leads to primary liver-cell cancer, researchers now believe that Hepatitis C also contributes to its formation. Primary liver-cell cancer is cancer which originates in the liver, as opposed to metastatic cancer, which spreads to the liver from other regions of the body.

But Resnick's study did not determine the number of B positive patients, and Associate Professor of Medicine Dr. Bruce D. Walker says that it is not clear that Hepatitis C alone, rather than untested-for Hepatitis B virus or another causative agent, is sufficient to cause liver-cell cancer.

Resnick insists that both viruses are prevalent in liver-cell cancer--not as cofactors but instead working independently. He says it can be shown that the absence of one virus make the other more probable.

In the majority of cases, the Hepatitis C virus is spread through blood or blood products and can be acquired through sexual intercourse, blood transfusions and intravenous drug use.

Liver-cell cancer is most prevalent in Asia and Africa. But because such cancer is responsible for less than one percent of all cancer-related deaths in the U.S., Mallinckrodt Professor of Medicine Dr. Kurt J. Isselbacher says Resnick's research is not as crucial to U.S. citizens as those in other parts of the world.

Researchers say that testing positive for the Hepatitis C virus does not necessarily lead to liver-cell cancer. And even when it does, the development is a long and not well-understood one.

Isselbacher says that developing the cancer can take more than 20 years and that a malignant state may not be reached until 40 to 50 years after acquiring the hepatitis virus.

While liver-cell cancer may not be a pressing concern to U.S. residents, researching this area is of importance to the scientific community.

"Identifying the mechanism by which the Hepatitis C virus infection is involved in malignant transformations of cells should provide important insight into the role of the virus in human cancer," says Walker.