Young adults who are overweight or obese have an increased risk of pancreatic cancer, and being obese at an older age is associated with a lower overall survival rate for patients with pancreatic cancer, according to a study in the June 24 issue of JAMA.

As the prevalence of overweight and obesity have rapidly increased during the last 2 decades, accumulating evidence has emerged that excess body weight is a risk factor for pancreatic cancer. "However, to our knowledge, no study has explicitly reported the association between excess body weight across an individual's life span and the risk of pancreatic cancer or identified at which ages the key predisposing weight change usually occurs," the authors write.

Donghui Li, Ph.D., of the University of Texas M. D. Anderson Cancer Center, Houston, and colleagues conducted a study to determine the associations between body mass index (BMI) over a lifetime and pancreatic cancer risk, age at onset, and overall patient survival. The study included 841 patients with pancreatic cancer and 754 healthy individuals matched by age, race, and sex. Height and body weight histories were collected by personal interview starting at ages 14 to 19 years and over 10-year intervals progressing to the year prior to recruitment in the study.

The researchers found that individuals who were overweight (a BMI of 25-29.9) from the ages of 14 to 39 years or obese (a BMI of 30 or greater) from the ages of 20 to 49 years had an associated increased risk of pancreatic cancer, independent of diabetes status. The association between average BMI (per 5-unit increase) and risk of pancreatic cancer was stronger in men than in women. The association was statistically significant for each age group from 14 to 69 years in men but only from ages 14 to 39 years in women. The estimated association of average BMI (per 5-unit increase) with cancer risk also was slightly stronger in ever smokers than in never smokers. It was estimated that 10.3 percent of never smokers and 21.3 percent of ever smokers had pancreatic cancer attributable to being overweight or obese at an early age prior to cancer diagnosis (i.e., from the ages of 14-59 years).

Individuals who were overweight or obese from the ages of 20 to 49 years had an earlier onset of pancreatic cancer by 2 to 6 years (median age of onset was 64 years for patients with normal weight, 61 years for overweight patients, and 59 years for obese patients). Compared with those with normal body weight and after adjusting for all clinical factors, individuals who were overweight or obese from the ages of 30 to 79 years or in the year prior to recruitment had reduced overall survival of pancreatic cancer regardless of disease stage and tumor resection status.

"While our observations require confirmation, they provide support for a role of excess body weight in the development and progression of pancreatic cancer," the authors conclude.

In an accompanying editorial, Robert R. McWilliams, M.D., and Gloria M. Petersen, Ph.D., of Mayo Clinic, Rochester, Minn., comment on the findings regarding BMI and risk of pancreatic cancer.

"The study by Li et al represents an incremental advance in the understanding of clinical factors contributing to pancreatic cancer development and progression. In particular, the survival analyses illustrate how epidemiological studies that include retrospective information gathering, combined with prospective follow-up, are helpful in establishing survival factors outside of the clinical trial setting. The biological bases for how overweight and obesity contribute to younger age of diagnosis, increased risk for pancreatic cancer, and poorer survival in pancreatic cancer require further investigation. Understanding these associations will provide much needed clues for targeting potential preventive and therapeutic strategies for this extremely aggressive and resistant type of cancer."