June 10, 2002 LOS ANGELES, June 10 -- Asian-American women have traditionally had a lower risk of breast cancer than others, but epidemiologists at the Keck School of Medicine of USC and USC/Norris Comprehensive Cancer Center have found that their breast cancer rates have been rising.
Cases of breast cancer among Japanese-American women, in particular, have been increasing rapidly, according to research published in the June 10 issue of the International Journal of Cancer.
The study is based on cancer cases reported in the mid-to-late 1990s to the Los Angeles Cancer Surveillance Program (CSP). The registry records cancers throughout Los Angeles County, the most populous and probably most ethnically diverse county in the nation. Breast cancer rates in Los Angeles are similar to rates nationwide.
Researchers found that the breast cancer incidence rates for Japanese and Filipino women were about double those for Chinese and Korean women, and rates rose during the 1993-1997 period for all except Chinese women.
"Although Asian-American women in the past have had low breast cancer rates, that appears to no longer be the case," says Dennis Deapen, professor of preventive medicine and director of the Los Angeles County CSP. "And if trends from the 1990?s have continued, rates among Japanese-American women in Los Angeles County may have surpassed those of non-Hispanic white women, who have historically had the highest rates of breast cancer."
The study indicated the following about breast cancer:
* Among Asian women 50 years or older, diagnosed cases increased about 6.3 percent a year during the five-year period. Among non-Hispanic white women 50 years or older, diagnosed cases increased about 1.5 percent a year during the same time period.
* In 1997, Asian-American women experienced 78 cases per 100,000 women. Non-Hispanic whites had about 129 per 100,000, African-Americans had about 98 per 100,000 and Hispanics had about 64 per 100,000.
* Breaking down Asian-Americans by national origin shows disparities. In 1997, Japanese women experienced 114 cases per 100,000 women. Flipinas had about 98 per 100,000, Chinese women had about 51 per 100,000 and Korean women had about 45 per 100,000.
"Breast cancer incidence for Japanese-American women in Los Angeles County is the highest reported anywhere in the world," Deapen notes. In Japan itself, studies have shown that breast cancer incidence also has increased dramatically, more than doubling from 1960 to the late 1980s. The Japanese lifestyle has become increasingly Westernized, study authors note, influencing factors known to increase risk for breast cancer: having fewer children, engaging in less physical activity and experiencing increasing obesity. Japanese are also eating more fats and fewer soy products.
Research has shown that when Asian women migrate to the United States, breast cancer risk increases in subsequent generations. Among the four Asian groups analyzed in this study, Japanese were the first population to migrate to Los Angeles County in substantial numbers, followed by Filipinos. Chinese and Koreans tend to be more recent and less acculturated immigrant populations.
Deapen and colleagues note that the trends point out the need for increasing awareness of breast cancer as a significant health hazard among Asian-American women, especially those of Japanese descent. Although Asian-American women have traditionally had lower-than-average breast cancer risk, physicians need to know that is no longer true?and breast cancer screening among such women is just as important as it is in other groups.
Adds Deapen: "The rapid increase in cancer rates also suggests that outside factors?such as diet and exercise?are prominent in risk, and these factors can potentially be altered."
Dennis Deapen, Lihua Liu, Carin Perkins, Leslie Bernstein and Ronald K. Ross. "Rapidly Rising Breast Cancer Incidence Rates Among Asian-American Women." International Journal of Cancer, June 10, 2002.
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