Dana-Farber study links obesity and lack of exercise to pancreatic cancer
Charles Fuchs, MD
Chalk up another reason to exercise regularly and keep off the pounds. A new study by researchers at Dana-Farber, Brigham and Women's Hospital (BWH), and the Harvard School of Public Health (HSPH) has found that pancreatic cancer rates are much higher in people who are substantially overweight and physically inactive than in those who are fit and maintain a normal weight.
The study, published in the Aug. 21 issue of the Journal of the American Medical Association, provides the strongest evidence to date that people can take steps, in addition to not smoking, to reduce their chances of developing pancreatic cancer, a notoriously difficult disease to treat.
"The message is that there is something people can do to protect themselves from pancreatic cancer," says the study's senior author, Charles Fuchs, MD, of DFCI's Department of Adult Oncology. "Moderate exercise on a regular basis can substantially reduce one's chances of developing the disease, as can losing weight for those who are seriously overweight."
Pancreatic cancer is the fifth-leading cause of cancer-related deaths in the United States. Almost 30,000 people nationally are diagnosed with it every year, and an equal number die of it. Only three percent of those who have the disease are alive five years after diagnosis. For those whose cancer has spread beyond the pancreas, the median survival time after diagnosis is just six months.
The long odds facing patients who cannot be surgically cured has raised the importance of preventing pancreatic cancer. Until now, however, no environmental factor other than cigarette smoking has been widely accepted as increasing one's chances of contracting the disease.
Two strikes
Scientists are not sure how obesity and lack of physical activity combine to raise a person's risk of pancreatic cancer, but both factors may increase an individual's level of insulin and blood glucose (sugar). Previous investigations suggest that excessive insulin levels may promote the growth of certain cancers.
In the current study, researchers used data from the Nurses' Health Study and the Health Professionals' Follow-up Study. These projects, conducted by researchers at BWH and HSPH, regularly gather health information on more than 150,000 female nurses and male health workers across the country. Participants report their physical activity, diet, weight, and other health measures.
An analysis of data covering 15 years found that people classified as obese (those with a body mass index — a metric measure of weight divided by height squared — above 30) were 72 percent more likely to develop pancreatic cancer than people of normal weight. The analysis also found that men and women who walk or jog four or more hours per week had a 50 percent lower risk of contracting pancreatic cancer than those who exercise less than 20 minutes per week.
"We have shown that losing weight and exercising — in addition to the many other benefits they provide — can significantly reduce one's chances of developing cancer of the pancreas," remarks lead author Dominique Michaud, ScD, of the National Cancer Institute, who participated in the research while at HSPH. "Physical activity has a considerable protective effect, especially among those who are overweight."
Fuchs adds that the research could promote insights into the basic causes of pancreatic cancer. Future investigations will examine the role of insulin and related hormones as risk factors. According to Fuchs, a better understanding of the disease's causes could provide better therapeutic approaches.
Source: Inside the Institute, Sept. 11, 2001