A new study finds liver cancer incidence rates continue to increase in some low-risk parts of the world such as North America, and are decreasing in some of the highest risk countries of Asia. Despite this, the incidence rates in Asian countries remain twice as high as those in Africa and more than four times as high as rates in North America. The study will be published in an upcoming issue of Cancer Epidemiology（流行病学） Biomarkers and Prevention and appears early online.

Using data from the International Agency for Research on Cancer, American Cancer Society epidemiologists Melissa M. Center, MPH and Ahmedin Jemal, PhD examined recent trends in liver cancer incidence rates from 1993 to 2002 for 32 cancer registries worldwide. They also examined the male to female rate ratios for these and four additional registries, based on the 1998 incidence data.

They found liver cancer incidence rates for both men and women increased from 1993 to 2002 for eight of the 32 cancer registries considered in the analysis. Increases were largely confined to economically developed countries of Western Europe, North America, and Oceania and may be partly due to increased chronic¹ HCV infection as a result of unscreened blood transfusions²（输血） and contaminated（受污染的） needles used for medical purposes and with widespread intravenous（静脉内的） drug use in previous decades. In contrast, rates decreased in both men and women in five registries including three in Asia. Despite this, incidence rates in Asian countries remain three to four times higher than those in low-risk areas with increasing rates. Male to female rate ratios varied³ from 0.9 in sub-Saharan African and South American registries to 5.0 (five men for every woman diagnosed) in France and Egypt.

The authors conclude that liver cancer incidence rates continue to increase in some low-risk parts of the world, while they are now decreasing in some of the highest risk countries in Asia. Additional studies looking at causation are needed, they say, to further elucidate⁴（阐明，说明） factors contributing to these divergent（相异的，分歧的） liver cancer incidence trends worldwide.

"We hope our description of international liver cancer incidence trends may stimulate⁵ studies to further illustrate⁶ etiologic（病因学的） factors associated with these divergent liver cancer incidence trends worldwide," said Ms. Center.