A steady influx of immigrants living with hepatitis C virus (HCV) infection and a high prevalence of the disease among baby boomers can help explain the increasing rates of liver cancer in the United States, according to two new studies conducted by researchers at the Mayo Clinic in Rochester, Minnesota, and reported in Mayo Clinic Proceedings.

“The studies illuminate the importance of identifying people with risk factors in certain populations to help catch the disease in its early, treatable stages,” said W. Ray Kim, MD, a Mayo Clinic specialist in gastroenterology and hepatology and lead researcher of one study.

According to Kim and his colleagues, data from the Rochester Epidemiology Project—encompassing an entire county’s inpatient and outpatient records—determined the region’s liver cancer prevalence to be 6.9 per 100,000 people. This rate was higher than the national average, estimated to be 5.1 per 100,000, according to the National Cancer Institute.

More important, Kim’s team found that the causes of liver cancer have shifted. Its primary source is now hepatitis C, where two decades ago it was most often the result of diseases such as alcoholic cirrhosis.

“The liver scarring from hepatitis C can take 20 to 30 years to develop into cancer,” said Kim. “We’re now seeing cancer patients in their 50s and 60s”—baby boomers born between 1945 and 1965—“who contracted hepatitis C 30 years ago and didn’t even know they were infected.”

Eleven percent of the liver cancer cases in the study resulted from obesity-related causes such as fatty liver disease. Kim warned that increasing national obesity rates could lead to an even greater upswing in liver cancer rates.

The second study, conducted by Abdirashid Shire, PhD, and his Mayo colleagues, suggests that careful attention needs to be given to U.S. immigrant populations, particularly for those hailing from countries where blood-borne infections are common. (Often times, hepatitis is contracted through contaminated medical equipment as opposed to injection drug use.)

Focusing on the Somali population, which is growing in the United States, particularly in Minnesota, Shire’s team confirmed that chronic hepatitis B infection—common in many East African and Asian countries—is contributing to liver cancer rates among immigrate patients. What surprised Shire’s team, however, was the finding that a significant percentage of liver cancer cases in the Somali population were attributable to HCV infection, which had not been known to be significantly prevalent.

“The study suggests that screening for hepatitis C would be helpful for the Somali population and would enable close surveillance of liver cancer among those at risk,” Shire said. “That would greatly improve treatment and survival of Somalis with this type of cancer.”