Researchers found that colorectal cancer risk in Californian Latinos vary widely based on their country of origin, according to study findings published in Cancer Causes & Control (doi:10.1007/s10552-015-0691-4).
Approximately 14.7 million Latinos live in California. They represent 38.4% of the California state population and 27% of the entire US Latino population, according to the US Census Bureau.
“Hispanics are a very heterogeneous population, which is not really recognized in most cancer studies,” said Mariana Stern, PhD, a cancer epidemiologist, and associate professor of preventive medicine in the Keck School of Medicine of University of Southern California (USC) in Los Angeles, and lead author of this study.
“Their risk factors might be different; their clinical characteristics could be different. We have to zoom into these observations and understand these disparities because they may affect how patients are educated about the disease and how they are treated by doctors.”
Using California Cancer Registry data, the USC researchers examined the profiles of 36 133 Latinos and 174 710 whites whose colorectal cancer was diagnosed between 1995 and 2011. Latinos were further identified by their location of origin: Mexico, Cuba, Puerto Rico, Central or South America, or not specified.
“Most of the information we have on the molecular characteristics of colorectal cancer comes from the white population,” said Stern, who is Latina. “There is little information specific to Latinos. Plus, they are typically clumped as a group.”
The study found that Latinos from Mexico have the lowest risk for colorectal cancer compared with other Latino subgroups. More Mexicans (20%) and Central or South Americans (20%) had colorectal cancer diagnoses before age 50 years compared with other Latino subgroups.
Among Latinos in California, Cuban patients with colorectal cancer had the highest proportion of deaths (63%), followed by Puerto Ricans (58%). Mexicans had a higher percentage of rectal cancer (35%) than other Latino subgroups.
“We have pioneered surveillance of ethnic differences in cancer risk,” said Lihua Liu, PhD, assistant professor of clinical preventive medicine at Keck Medicine of USC and a research scientist in the Los Angeles Cancer Surveillance Program, and senior author of the study. “We have previously shown dramatic differences in cancer risk among Asian subgroups. It’s time to also examine the heterogeneity within Latinos.”
Hospitals and clinics in California, however, do not have a standardized practice for collecting detailed ethnic and birthplace information, resulting no recorded information on country of origin for a large proportion of Latino patients that poses a notable weakness of the study.
Standardizing ethnic and birthplace data collection can help guide future cancer control strategies, Liu said. The objective is to reduce the impact of cancer, the leading cause of death in the Latino community. In contrast, the number 1 cause of death among whites is heart disease, followed by cancer.
Genetics, varying degrees of intermixing, and acculturation to the US lifestyle influence colorectal cancer incidence rates. For example, Latinos from the Caribbean generally have more African and fewer indigenous American forefathers. People from Mexico, however, have a larger proportion of indigenous American ancestry than Puerto Ricans or Cubans, Stern said.
“Maybe the biology of people from Mexico protects them from developing colorectal cancer,” she added. “This has been reported for breast cancer too. The heterogeneity of Latino populations presents a unique opportunity to disentangle the complex role of socio-demographics, culture, lifestyle, and genetics as potential determinants of colorectal cancer risk among Latinos and other populations.”