Asian Americans Show Different Cancer Pattern Than Whites

Roxanne Nelson, BSN, RN

September 30, 2016

Asian Americans have overall lower cancer mortality rates as compared with non-Hispanic whites (NHWs), but certain exceptions point to differences in biological or lifestyle risk factors. For example, stomach and liver cancer mortality are very high in several Asian American groups.

These findings come from the first report to comprehensively document trends and patterns of cancer mortality among six major Asian American ethnic groups. The report was published in the October issue of Cancer Epidemiology, Biomarkers & Prevention.

The authors suggest that cancer prevention and screening efforts geared to specific ethnic groups may be beneficial.

Stomach and Liver Cancer

Two cancers found at a much higher rate among Asian Americans than among NHWs are stomach and liver cancer, the report notes.

Death from stomach cancer accounted for about 10% to 15% of cancer mortality among ethnic Koreans and approximately 5% to 10% of cancer related mortality among Chinese, Japanese, and Vietnamese.

In contrast, stomach cancer accounted for less than 2% of all cancer deaths among NHWs.

Death due to liver cancer was also generally much higher in the Asian American population. It accounted for 22% of cancer deaths in Vietnamese males, 12% of Chinese males, and 10% of Vietnamese females.

Again, in contrast, liver cancer was responsible for less than 2.5% of cancer related deaths in NHWs.

"We know that certain cancers, such as liver cancer, that are related to infections such as hepatitis B are more common in China," said lead author, Latha P. Palaniappan, MD, MS, a clinical professor of medicine at Stanford University School of Medicine in California.

"Liver cancer is also more common in Chinese Americans," she told Medscape Medical News. "We have a publication under review that examines nativity status — foreign-born vs US born — and we do see higher rates of some cancers among foreign-born populations, possibly due to higher-risk exposures to certain viruses in the country of origin."

Teasing Out Factors

As a group, Asian Americans have surpassed Hispanics as the fastest-growing racial/ethnic group in the United States. There are currently 17.3 million Asian Americans in the United States, representing 5.6% of the total population, and by 2050, it is estimated that their population will exceed 40 million.

A new version of the US death certificates was implemented in 2003, which detailed Asian ethnicity for six major subgroups: Asian Indian, Chinese, Filipino, Japanese, Korean, and Vietnamese.

Before 2003, only seven states collected detailed information on Asian ethnicity, which in turn limited knowledge of how cancer affected each of these separate groups. But even then, it can be difficult to gauge the converging effects of biology and lifestyle factors on cancer mortality risk.

"The US death records only contain data for first- and second-generation Americans and do not capture any further generational data," said Dr Palaniappan. "There is ample data to suggest that immigrants who acculturate to Westernized lifestyles tend to slowly mirror health of the native population over time, but it is poorly understood how this may differentiate among diverse racial/ethnic populations."

It is also unclear how immigrant status may affect certain cause-specific deaths, such as cardiovascular disease and cancer, which may be highly influenced by factors related to place of migration, such as socioeconomic environment, social norms, and local health policies, she noted.

"As an example, smoking rates may be much lower in the United States, which is important for lung cancer prevention; however, sedentary lifestyles and poor diets common to Western countries may increase risks for cardiovascular disease," Dr Palaniappan pointed out. "It is also important to look at Asian subgroups separately, instead of as a whole, because patterns are different."

Lung cancer mortality is one case in point. Even though mortality trends are stable or declining for most of the population, there has been a modest increase in lung cancer deaths among Chinese, Filipina, and Japanese women.

Breast cancer is another example, she explained. "Breast cancer deaths accounted for about 20% of all Filipino and Asian Indian cancer deaths, compared with 15% of cancer deaths among non-Hispanic white women. But among other Asian American women, breast cancer death rates were significantly lower than those for non-Hispanic white women."

Variance Among Different Groups

For their study, the authors obtained data on 85,616 cancer-related deaths from 2003 to 2011 from the National Center for Health Statistics. They examined cancer-related mortality for Asian Indians, Chinese, Filipinos, Japanese, Koreans, and Vietnamese and compared it with mortality for NHWs as the reference population.

When looking at the major cancer types, they found that lung cancer was the leading cause of cancer-related death for men in all Asian American groups, as well as for Chinese, Japanese, and Vietnamese women. Among Filipino and Chinese men, lung cancer accounted for approximately 30% of all cancer-related deaths.

But the overall mortality burden for male lung cancer in most Asian American groups was about half of that seen in NHWs; in females, it was half to one third. This was particularly true for Asian Indians of both sexes, who had markedly lower lung cancer mortality rates than both NHWs and all other Asian ethnic groups.

The authors also found that while lung cancer mortality had stabilized or was declining among men in all groups, the trend was not seen in women. For Chinese, Filipina, and Japanese women, there was a nonsignificant upward trend.

For female breast and ovarian cancers, Filipinas had the highest rates of breast cancer mortality compared with other Asian groups, but their mortality rates were still lower than those of NHWs. That said, breast cancer accounted for 19.5% of all cancer deaths in this group, compared with 14.6% in NHW women.

Ovarian cancer mortality was also lower among Asian groups. In NHW women, the mortality rate was 8.8 (age-adjusted mortality rate), while among all Asian groups, the rate was half that or less. However, there was a spike in the numbers — ovarian cancer death accounted for 10% of female Asian Indian cancer mortality, which is about twice the proportion in NHW women.

Among men, prostate cancer is the second leading cause of cancer death in NHW males but ranks third for most of the American Asian groups. Filipino men had the highest rates of prostate cancer mortality and Vietnamese men the lowest, but a slightly downward trend in prostate cancer mortality was noted for all groups.

Finally, the rates of death from colorectal cancer were similar between NHWs and Asian groups. Colorectal cancer accounted for about 10% of total NHW cancer mortality and about 9% to 11% for most Asian groups, but the rate was higher for Japanese, at 13%. Japanese of both sexes had the highest rates among Asian groups, while Asian Indians had the lowest.

Even though the adjusted rates of mortality for colorectal cancer were slightly lower among Asians than NHWs, the authors note that the differences were not as large as those seen for other malignancy types.

Given the differences in cancer mortality, Dr Palaniappan suggested that diverse Asian subpopulations should have targeted cancer screening guidelines tailored to the unique cancer risks in their communities.

This work was supported by grants from the National Institutes of Health. One coauthor reports receiving a commercial research grant from Genentech; none of the other authors have disclosed any relevant financial relationships.

Cancer Epidemiol Biomarkers Prev. 2016;25:1371-1382. Abstract

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