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."
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.
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."