Rates of breast cancer occurrences in Asian women rising among specific ethnic groups

Data Challenges Myth About Population Traditionally Thought Not Affected

U.S.-Born Chinese And Filipino Women And U.S.- And Foreign-Born Japanese Women Have Highest Rates In California

Research scientists from the Cancer Prevention Institute of California (CPIC) released the results of a study of breast cancer in Asian women which examined their cancer rates by ethnicity, age and immigrant status.  The findings challenge the notion that breast cancer rates are uniformly low across the population of Asian women and indicate rising rates of occurrences in specific ethnic groups.  CPIC scientists studied Asian populations in California, the state with the largest and most diverse Asian population in the U.S.

Study data was drawn from the California Cancer Registry, comprising three of the National Cancer Institute's Surveillance, Epidemiology and End Results program registries.  U.S. Census data, Social Security information and other statistical sources supplemented the data to examine cancer occurrences in California residents during the years from 1998 to 2004.

Breast cancer is the most diagnosed cancer in U.S. women.  Findings from the CPIC study, under the direction of CPIC Research Scientist Scarlett Lin Gomez, Ph.D., were recently published online in the American Journal of Public Health. They revealed that rates vary by specific ethnicity and also by country of origin – with nearly a three-fold difference between some ethnic populations.  The highest breast cancer rates in Asian women are in Japanese women, regardless of place of birth, and the lowest rates are in foreign-born Laotian women.  For U.S.-born Asians, Chinese and Filipino women carry the highest risk, which has been rapidly increasing over time.  Rates among U.S.-born Chinese and Filipino women under age 55 were even higher than those among whites, which was particularly unexpected.

CPIC scientists' discovery that there is a higher breast cancer rate in Asian women living in the U.S. than in their home countries raises questions regarding environmental and non-genetic factors in breast cancer causation.  

"Health disparities and inequities experienced by Asian Americans largely have been under-described because of stereotypes about supposed positive health profiles and a lack of detailed data about the many different populations within the group typically classified as 'Asian'," said Dr. Gomez. "Examining data enhanced to enable the study of cancer incidence in U.S. immigrant groups, as we did in this study, is an important step toward building a base of evidence that can inform health policies for U.S. Asian populations."

According to Dr. Gomez, further research is needed to better understand underlying factors.  Changes in reproductive factors (e.g., higher age at first live birth, lower breast feeding rates, earlier onset of menstruation), lifestyle factors (e.g., diet) and other environmental exposures may be affecting the rates.

SOURCE Cancer Prevention Institute of California