Among Asian-Americans living in California, Laotian/Hmong-Americans have the lowest survival rates for the most common type of liver cancer, a new study by researchers with the UC Davis School of Medicine has found.
The study, the largest population-based examination of liver cancer rates among Asian-Americans, highlights a profound disparity that calls for targeted outreach to detect and treat the disease earlier among Laotian/Hmong-Americans, said Moon Chen Jr., a professor of hematology and oncology in the UC Davis School of Medicine.
"We knew that liver cancer is the most significant and prominent cancer health disparity affecting Asian-Americans. But we wanted to look at which Asian-American population was most at risk of dying from the disease," said Chen, who also is associate director of cancer control at UC Davis Cancer Center.
"If we do an intervention, not only do we have to address the characteristics of a particular disease. We have to figure out how to reach the specific population that is affected."
The study, "Disparities in Hepatocellular Carcinoma Survival among Californians of Asian Ancestry, 1988-2007," is published online in the journal Cancer Epidemiology, Biomarkers & Prevention. The research was conducted by UC Davis along with colleagues at the California Department of Public Health and UC San Francisco.
The study used California Cancer Registry data from more than 6,000 Asian-American patients diagnosed with hepatocellular carcinoma (HCC) between 1988 and 2007. It found stark differences in survival rates among the nine largest Asian-American groups in California, including Chinese, Filipino, Vietnamese, South Asian, Korean, Japanese, Laotian/Hmong, Cambodian and Thai.
Although much more prevalent in other parts of the world, liver cancer incidence in the United States is on the rise, and death rates from the disease have increased faster for both men and women than for any other type of cancer. Medical interventions for liver cancer are limited and may include surgery and liver transplantation. Hepatocellular carcinoma is the most common type of liver cancer.
Liver cancer among Asian-Americans is primarily related to infection with hepatitis B, which is endemic in many parts of Asia. The virus can pass from mother to unborn child, developing into cancer over many years.
The Hmong are an Asian ethnic group from the mountainous regions of China, Vietnam, Laos and Thailand. During the Vietnam War, thousands of Hmong were enlisted by the United States in Laos to fight communist insurgents. Many Hmong war refugees were resettled in the United States after the war.
The study found significant disparities in survival rates for Asian-Americans diagnosed with liver cancer. The median survival rate for the Laotian/Hmong Americans involved in the study was just one month. It was three months for the Cambodian-Americans, and four months for the Thai- and Filipino-Americans. The survival rate was six months for the Chinese- , Japanese- and Vietnamese-Americans. The Korean- and South Asian-American survival rate was seven months.
"The Laotian-Hmong have the worst survival rates for liver cancer — between one to two times greater than the aggregate of the Asian-American groups, which already is poor," Chen said.
Chen pointed out that, for all Americans, the liver cancer death rate is less than 10 percent after five years.
Researchers also discovered that Laotian/Hmong were far more likely to be diagnosed with cancer at later stages of the disease, which led to the poorer survival outcomes. The group also was the least likely to receive any kind of treatment, such as a liver transplant. Only 3 percent of Laotian/Hmong-Americans with liver cancer underwent surgery or liver transplantation, compared with 22 percent of other Asian-Americans studied.
Other important findings from the study are that Southeast Asian-Americans — those of Cambodian, Thai and Laotian/Hmong ancestry — were relatively young, diagnosed before age 50 more often than other groups. More than half of the Hmong/Laotians belonged to the lowest socio-economic group.
Liver cancer is considered a silent killer because it is not typically symptomatic until it is advanced, said Christopher Aoki, a co-author of the study and former gastroenterology and hepatology fellow and faculty member at UC Davis.
"That's why increasing awareness among the populations and among the physicians who take care of these patients is very important," Aoki said.
Now a liver specialist at The Queens Medical Center in Honolulu, Aoki said physicians must first identify those patients at risk for exposure to hepatitis B infection, and those who test positive should be screened for liver cancer.
Chen also emphasized that the findings point to the importance of developing liver cancer screening and other awareness materials in the language spoken by the individual groups affected so that they understand the importance of early detection.
Chen is also principal investigator of the Asian American Network for Cancer Awareness, Research and Training (AANCART), a National Cancer Institute-funded program to reduce cancer disparities in Asian-American populations. He also leads a research program at UC Davis focused on interventions for Hmong, Vietnamese and Korean Americans at risk for liver cancer.
"We believe that hepatitis B-induced liver cancer can be controlled," he said. "We have an effective vaccine, and with the combination of both screening and treatment we can eventually eliminate liver cancer."