Based on a comprehensive study that included more than half the U.S. Asian-American and Native Hawaiian and Other Pacific Islander (NHOPI) populations, a team of scientists led by members of the Keck School of Medicine of USC and Cancer Prevention Institute of California (CPIC) has produced the first-ever analysis of national cancer incidence trends among 11 Asian-American and NHOPI groups.
The researchers examined rates and trends from 1990 through 2008, using data collected by 13 registries of the National Cancer Institute’s Surveillance, Epidemiology and End Results (SEER) Program. The groups studied in detail include Asian Indians/Pakistanis, Chinese, Filipinos, Guamanians/Chamorros, Japanese, Kampucheans (Cambodians), Koreans, Laotians, Native Hawaiians, Samoans and Vietnamese.
The studies reveal substantial disparities and complexities in cancer incidence patterns and trends among these population groups. Their findings appear in a pair of articles published first online in the Journal of the National Cancer Institute.
“These population groups are so different from each other in terms of culture, language, history, socioeconomic status and risk exposures,” said Lihua Liu, PhD, assistant professor of clinical preventive medicine at the Keck School and lead author of the NHOPI analysis. “Putting them all into one group masks the unique cancer patterns and experiences of each subgroup.”
In their article, Liu and colleagues report clear differences in cancer incidence rates among NHOPI subgroups and between NHOPIs and non-Hispanic whites by cancer type.
“One of our most unique observations is the seemingly migrant effect on Native Hawaiians’ cancer risk,” Liu said. “Their change in cancer risk is similar to what we see in immigrants, which strongly indicates the environmental influence on cancer incidence.”
Native Hawaiians living in Hawaii experienced higher risks for lung, breast and uterine cancers, but lower risks for colorectal and prostate cancers, as compared to the Native Hawaiians living on the U.S. mainland. Liu says that future research designed to understand the causes for the geographic differences could help reduce cancer disparities among Native Hawaiians.
The Asian-American study, led by CPIC Research Scientist Scarlett Lin Gomez, PhD, found that prostate was the most common type of cancer among men, followed by lung, colorectal, liver and stomach cancers.
When looked at individually, however, important differences arise. For instance, while breast cancer was the most common form of cancer among women, not all groups experienced the same incidence or trends over the study period. Chinese women experienced a greater than 1 percent increase annually in breast cancer rates throughout the nearly 20-year period. At the same time, Japanese women experienced an even greater annual increase (2.7 percent) between 1990 and 1998, but then a nearly two percent annual decrease after that.
This research was supported by the National Cancer Institute’s SEER Program under contract HHSN261201000035C awarded to the University of Southern California, contract HHSN261201000140C awarded to the Cancer Prevention Institute of California and contract HHSN261201100412P awarded to one of the authors.