While colorectal cancer is recognized the third most common cancer in the country, behind lung and prostate in men and lung and breast in women, a group of Tulane University researchers suspected it’s even more prevalent in pockets of their local region in south central and southwest Louisiana.
Once Tay-Sachs disease, an inherited disorder that destroys nerve cells in the brain and spinal cord, was established as predominant in the Cajun population, Jordan Karlitz, MD, Division of Gastroenterology at Tulane University School of Medicine and adjunct faculty at the LSU Health New Orleans School of Public Health, began to suspect a similar link might exist between Cajun inhabitants of Louisiana and colorectal cancer.
In October they released findings that white men in the Louisiana Acadian parishes — those in which French is commonly spoken — have colorectal cancer rates that are among the highest in the U.S.
First Founder Population Cancer Study
The research is generating a great deal of buzz in the cancer registry community as it’s the first in the U.S. to study a regional founder population in the U.S. for cancer. In medical terminology, a “founder population” is a distinct new population that has descended from an original, larger population. In this case, the Cajuns migrated in the 1700s from France first to Canada, then Louisiana where they settled in the state’s Acadian parishes.
“Founder populations are important to study as cancer susceptibility genes, potentially novel, may be discovered that may be important not only for the population in question, but for others worldwide who may share a similar remote ancestry,” Karlitz said.
Sure enough, rates of colorectal cancer increased in parallel with the proportion of French speakers, a marker for parishes with higher numbers of those with Cajun ancestry, said Karlitz.
While Karlitz hypothesized colorectal cancer rates would be high in the Acadian parishes, even he was surprised that they were the highest in the U.S. for white males.
The research team identified 18 Acadian parishes and stratified 2005-2009 cancer incidence data by age, ethnicity and gender by utilizing French language census data. They used data from the Louisiana Tumor Registry to uncover a total of 3,288 colorectal cancer cases in the Acadian region and 11,737 in Louisiana. They identified a subgroup of nine parishes with higher proportions of French speakers, a marker for the Cajun population. Colorectal cancer rates in whites and white males in the 18 parishes were statistically significantly higher than both Louisiana and U.S. rates. In the nine parishes, rates increased further; whites had an incidence of 56.1 per 100,000, 13% higher than Louisiana and 23% higher than the US rate. In white males, incidence was 72.6 per 100,000, 19% higher than Louisiana and 37% higher than the US rate. If the 9-parish region were considered a “state,” white males would have the highest colorectal cancer incidence in the United States by 11% compared with other white male populations.
“Kentucky was the state with the highest colorectal cancer rate in white males and our rates were still higher than Kentucky’s,” he offered.
Limitations of Cancer Registry Studies
Even with this compelling evidence, Karlitz said he still can’t go as far as saying there’s a definite genetic link.
For one, environmental factors haven’t been ruled out. “We’ll need to do a new study examining patients with lung and pancreatic cancers sharing environmental risk factors such as obesity or smoking,” he explained. “Incidences of these cancers were high, but not disproportionately so like colorectal cancer.”
It’s also logical that some aspect of the Cajun diet may be at the root of the increased cancer incidences. Karlitz acknowledged the possibility, but said further study would be needed.
“In general, dietary studies have been somewhat inconclusive regarding red meat as a risk factor for CRC. Also, it is not clear whether red meat consumption is higher (or lower) in the Acadian parishes compared to other areas,” he noted. “The Cajun diet has traditionally contained a lot of fruits and vegetables which can actually be protective for CRC.”
The study would’ve been impossible without the Louisiana Tumor Registry at the Louisiana State University School of Public Health and its data for cancer control and research, Karlitz noted. It’s an asset he hopes more researchers utilize in their respective states, even if they’re not part of the registry structure. But it’s wise to regard information from the registry as a starting point.
“There’s no better data source to get a global picture of a region,” stated Karlitz. “It’s population based, so there’s no data on individual patients. We don’t know exactly who is of Cajun ancestry or the specific risk factors of a smaller subset. What we can say is that where people speak French at home, there are higher rates of colorectal cancer but we can’t say for sure it’s because they’re Cajun.”
In addition to inspiring a burning question in future medical researchers, Karlitz hopes his work attracts more clinical research to the area. The study’s garnered attention in the local media and Karlitz is optimistic it will have an effect on screening.
“Just knowing that the rates are high in this area will prompt more people to get a colonoscopy,” said Karlitz.
Robin Hocevar is on staff at ADVANCE. Contact email@example.com.