Cancer incidence in the Hmong of central California, United States, 1987-94

The Hmong are an ethnic minority in China, some of whom migrated to the mountainous areas of North Vietnam, Laos, and Thailand in the 19th and 20th centuries. Because of their support for the United States during the Vietnam war, many Laotian Hmong fled to Thailand and eventually were re-settled in the US after the end of that conflict. Approximately 100,000 Hmong currently live in the US, of whom about half reside in the Central Valley of California, The purpose of this study was to measure cancer incidence in this unique new immigrant population. Using the resources of the Cancer Registry of Central California (CRCC), a population-based cancer registry cancer incidence in the Hmong was evaluated by calculating age-adjusted incidence rates as well as by calculating proportional incidence ratios. Compared with all races combined, elevated rates of cancer in the Hmong were observed for the following sites: nasopharynx, stomach, liver, pancreas, leukemia, and non-Hodgkin's lymphoma. Cervical cancer incidence overall was elevated, but more noteworthy, invasive cervix cancer rates were much higher than expected. Lower cancer rates were found for breast, prostate, and colorectal cancer. Hmong also experienced advanced stage and grade of disease at diagnosis for many cancer sites in addition to cervical cancer, which may be explained by cultural factors, including avoidance of Western medical care and low rates of participation in screening programs. This population should be followed closely and monitored for patterns of cancer incidence in the future since it provides a natural laboratory for studies of cancer etiology as this population gradually becomes acculturated to the Western lifestyle.