Previous research demonstrated that obesity increases the risk for pancreatic cancer, but this is the first prospective study to show that a high body mass index (BMI) reduces survival after pancreatic cancer diagnosis.
Researchers from the Dana-Farber Cancer Institute, Harvard Medical School, and Harvard School of Public Health collected data from 121,000 female participants in the Nurses’ Health Study and 51,000 male participants in the Health Professionals Follow-up Study. Over 24 years of follow-up, the researchers identified 958 persons with pancreatic cancer for whom data on BMI was available; 902 were included in the analysis.
When the researchers compared subjects with a BMI of 35 kg/m2 or higher to those with a BMI less than 25 kg/m2, they found that high baseline BMI was associated with reduced survival after pancreatic cancer diagnosis (hazard ratio [HR], 1.53; 95% CI: 1.11-2.09). Overall, the median survival time after diagnosis was 5 months, but patients with a lower BMI survived 2 to 3 months longer than obese patients.
Moreover, patients in the top 20% of survival time were more likely to be of normal weight than patients in the bottom 20%.
The effect on survival was even more pronounced for patients with long-standing obesity. For subjects with BMI records dating back 18 to 20 years before diagnosis, the HR for death was 2.31 (95% CI: 1.48-3.61) for those with a BMI of 30 kg/m2 or higher compared with those with a BMI of 25 kg/m2 or lower, suggesting that prolonged exposure to the effects of obesity has a greater impact on survival.
Patients with a high BMI also were more likely to be diagnosed at an advanced stage of cancer—73% of patients with a BMI of 30 kg/m2 or higher had metastatic disease at presentation, compared with only 59% of patients with a BMI of 25 kg/m2 or lower. Nevertheless, the increased risk for death among obese patients persisted after statistical analysis controlled for stage at diagnosis, suggesting that other factors associated with obesity also contributed to poorer survival.
“This study adds to mounting evidence for the role of weight control in improving outcomes for patients with cancer,” said senior study author Brian M. Wolpin, MD, MPH. “It also reinforces the importance of maintaining a healthy weight throughout life, which may lead to better outcomes after diagnosis and help prevent pancreatic cancer from developing.”
How obesity might reduce survival in pancreatic cancer is unknown. In their report, the investigators suggested that long-term obesity might cause chronic alterations in systemic metabolism and inflammation, which can promote malignancy. In addition, fatty infiltration of the pancreas might act locally to accelerate tumor growth. However, the researchers could not rule out the possibility that obese patients have higher complication rates from surgery or medical therapy, as well as more concomitant illnesses that would reduce survival.
“While our findings will not affect the way we treat patients today,” Dr. Wolpin said, “they provide new leads for investigating the molecular pathways that may be responsible for the survival difference between obese and healthy-weight patients. Hopefully, in the future, that research will bring new approaches for treatment of pancreatic cancer.”
Commenting on the study, Smitha Krishnamurthi, MD, of the American Society of Clinical Oncology, who was not part of the research team, said, “While previous retrospective studies suggested a link between obesity and pancreatic cancer survival, the prospective nature of this study makes the findings more reliable.”
1. Yuan C, Bao Y, Wu C, et al. Prediagnostic body mass index and pancreatic survival. J Clin Oncol. Oct 21 [Epub ahead of print].