A US study found that despite risk factors such as being overweight and smoking, blacks were more likely to die from pancreatic cancer than whites.

The cohort study was the work of Dr Lauren D Arnold, a postdoctoral research associate in the department of surgery at Washington University in St Louis, Missouri, and colleagues, and appears in the 1 September online issue of the journal Cancer Epidemiology, Biomarkers & Prevention.

Arnold told the media that:

“Reducing overweight/obesity and smoking will help reduce pancreatic cancer overall, as well as prevent other diseases.”

But she added that:

“We still have a long way to go towards understanding pancreatic cancer disparities.”

Most people die of pancreatic cancer within two years of diagnosis, because screening tools aren’t good enough and symptoms usually only appear too late, when the disease has already spread to other parts of the body.

Statistically, more black Americans are more likely to die of the disease than whites; figures for 2001 to 2005 from the National Cancer Institute show that blacks had a 32 per cent higher death rate.

Using data from the longitudinal Cancer Prevention Study II (CPS-II), Arnold and colleagues evaluated pancreatic cancer risk factors in whites separately from blacks to see if they might explain differences in disease rates and deaths.

CPS-II recruited over 1 million participants from 1982 and noted their race/ethnicity, medical history, health habits, deaths and other outcomes.

When Arnold and colleagues analysed the data, they found that:

  • Smoking ws the biggest risk factor for pancreatic cancer.

  • Risk of pancreatic cancer went up with BMI (body mass index, the ratio of a person’s weight to the square of their height).

  • Blacks had a 42 per cent higher risk of dying from pancreatic cancer than whites.

  • Blacks still had a higher risk of death from pancreatic cancer even when all other risk factors were taken into account.

The researchers concluded that:

“The inability to attribute excess disease in Blacks to currently known risk factors, even when combined with suspected risks, points to yet undetermined factors that play a role in the disease process.”

Arnold said:

“We hoped to find that by accounting for known and suspected pancreatic cancer risk factors, such as smoking, diabetes and BMI, and by looking at this in the context of race and gender, we’d be able to explain the higher rates of pancreatic cancer in blacks.”

“Unfortunately, we were unable to explain these differences,” she added.

Commenting on the study, Dr Maria Elena Martinez, an editorial board member of the journal that published the article, and who is also the Richard H. Hollen Professor of Cancer Prevention at the University of Arizona, and director of the Cancer Health Disparities Institute at the Arizona Cancer Center, said that although the researchers found differences in risk factor patterns, they didn’t explain the racial differences in pancreatic cancer deaths:

“The results most certainly point to the need for additional work to explain these racial disparities in risk of pancreatic cancer,” said Martinez.

“Factors other than those assessed by the researchers may be responsible for the disparities. These can include unidentified lifestyle and/or environmental factors, genetic factors or unique gene-environment interactions,” she suggested.

This study is unique in that there was a large group of participants, they were followed for a long period of time, and they were cancer-free at the start of the study period.

Arnold said one limitation of the study is that higher rates of death and illness could have been due to lack of or limited access to healthcare. But other studies show that access to healthcare may not be the problem in the case of pancreatic cancer disparities because both blacks and whites tend to be diagnosed when the disease is already at an advanced stage, impeding treatment and resulting in low survival.

“Our data do not explain what is causing these disparities, but we hope it encourages researchers to continue looking for reasons why blacks develop and die from pancreatic cancer at higher rates than whites,” said Arnold.

“Clinicians who have patients with a family history of pancreatic cancer or other risk factors for the disease should communicate the benefits of losing weight and quitting smoking, if anything, to help reduce their risk of pancreatic cancer,” she added.

“Are Racial Disparities in Pancreatic Cancer Explained by Smoking and Overweight/Obesity?”
Lauren D. Arnold, Alpa V. Patel, Yan Yan, Eric J. Jacobs, Michael J. Thun, Eugenia E. Calle, and Graham A. Colditz.
Cancer Epidemiol Biomarkers Prev first published online on September 1, 2009.
DOI:10.1158/1055-9965.EPI-09-0080

Additional sources: American Association for Cancer Research.

Written by: Catharine Paddock, PhD