August 6, 2009
Many Hispanic immigrants who relocate to the United States face much higher cancer rates than those in the country they left behind, new research shows.
While the U.S. might provide more cancer screening and often better health care overall, said Paulo Pinheiro, an epidemiologist with the University of Miami Miller School of Medicine and the study’s lead author, “For Hispanic populations, there are beneficial lifestyles associated with their origin that probably should be kept. There are lifestyles that may be more prevalent in the U.S. that probably should be avoided.”
Cancer can be 40 percent more common for Hispanics after they immigrate, the study showed — though it warned doctors not to rely on that figure alone.
Pinheiro and his colleagues found that cancer rates in these groups tend to rise or fall with expected rates among their American counterparts, but that rates for immigrants from Cuba, Mexico or Puerto Rico can be very different.
“Hispanic populations shouldn’t all be considered together. There are specificities to each one of them,” he said.
The University of Miami study looked at cancer rates among Florida residents and found that rates among Cuban immigrants closely followed those seen in white residents of the state, while Puerto Ricans “consistently showed the highest cancer rates of all Hispanic subpopulations.” Mexicans had the lowest cancer rates but had high rates of cancers typically associated with minority populations, such as stomach, cervix and liver cancer.
The study also looked at “New Latinos,” a varied group that included Hispanics who came from Spain, the Dominican Republic and South and Central American countries. These groups had low rates of lung cancer, high rates of thyroid cancer and high rates of cancer that would be expected in a minority population.
To conduct the study, researchers used numbers from the Florida cancer registry from 1999 through 2001, and used data from the 2000 census to generate estimates of cancer rates in the United States. They compared this to data from the International Agency for Research on Cancer, a division of the World Health Organization.
Researchers looked at rates of cancer incidence among Hispanics who had immigrated to the United States from Puerto Rico, Cuba and Mexico and compared them to the rates seen in their home countries. They also compared these rates to those seen in non-Hispanic whites and blacks in the U.S.
Experts not involved with the study noted that a pattern of typically increased cancer rates is not uncommon when a group immigrates to the U.S.
“This study is [reminiscent] of studies from the late 1960s that looked at immigrants from China and Japan to the U.S.,” said Dr. Otis Brawley, chief medical officer and executive vice president of the American Cancer Society. “They raise risk of cancer by immigrating and raise rates for second generation Americans even more so.”
Reasons for Trend Remain Unclear
While the study indicated a strong change in cancer rates among Hispanic immigrants to the U.S., it could not explain exactly why this occurred.
However, the researchers say the data provide some clues.
Pinheiro said that among the changes in cancer rates, one of the most striking is the rise in colorectal cancer rates, which nearly doubled among Puerto Ricans, nearly tripled among Mexicans and more than tripled among Cubans.
He said the changes can likely be attributed to diet — red meat, in particular, is far more popular in the U.S. than elsewhere.
Brawley agreed, noting that the trend has been observed in the past, as when Chinese immigrants came to the U.S.
“[The] major reason is diet changes,” he said. “Increased dietary fat and dietary obesity causes this. Rates were higher in the acculturated than those moving to U.S. Chinatowns.”
Pinheiro said that changes in patterns of tobacco and alcohol use and lack of physical exercise might also explain changes in cancer rates.
He acknowledged that higher rates of screening in the United States might account for some of the differences in cancer rates, but said that likely did not account for the significant changes in cancer rates.
“We look more for cancer in this country, for instance,” said Pinheiro.
Prostate cancer, which is heavily screened for in the U.S., provides one example. In the study, Puerto Rican immigrants, coming from a U.S. territory, had almost the same rates of prostate cancer, while the rates almost doubled in Mexican immigrants and nearly quadrupled among Cuban immigrants.
However, Pinheiro noted, the rates of cancers more commonly found in less developed countries dropped.
“Here we observe the decrease,” he said, noting that this would not be accounted for by reporting errors.
Brawley agreed. He said that more common screening in the U.S. likely had some effect on the numbers but said that “[I] doubt reporting changes anything and doubt this influences treatment.”
Further Categorization Necessary?
Pinheiro said one important thing to draw from the study was that Hispanics could not be lumped together as a single group in studies about ethnic groups and cancer.
At present, he said, he would like some separation among “Hispanic” by country of origin.
It would be especially useful, he said, in his own state. “Florida is so diverse, that of course we want that.”
However, he said, it may be hard to do because cancer registries are national, and most other states have a more homogenous Hispanic population, and, therefore, no use for a more specific registry.
“Because these standards are national, it’s so different,” said Pinheiro.
Dr. Jay Brooks, chairman of hematology/oncology at Ochsner Health System, agreed that better studies can’t be “lumping all people together.”
But more categorization presents a paradox.
As Pinheiro said, increased immigration will require more specific categorization for research. But as immigration increases, so will intermarriage between different Hispanic groups, making the U.S. Hispanic population (as well as the U.S. population in general) more homogenous.
Missing an Opportunity for Advancement?
While Pinheiro said greater categorization might ultimately lose its utility, he said that the time before that happens presents a unique opportunity to determine behaviors that may help prevent cancer.
He believes that in order to determine which behaviors influence cancer, researchers will need to do studies quickly among older Hispanic immigrants living in the U.S.
“We’re missing an opportunity here,” said Pinheiro. “There’s surprisingly [little] research thus far.”