Published: Oct 21, 2013
By Cole Petrochko, Staff Writer, MedPage Today

Obese patients with pancreatic cancer were more than twice as likely to die over an 18-to-20-year period than healthy-weight patients, researchers found.

Across two cohorts analyzing risk of death among pancreatic cancer patients, having a body mass index (BMI) of 35 or greater at 18 to 20 years pre-diagnosis was associated with a 2.31-fold increased risk of death (95% CI 1.48-3.61, P<0.001) compared with having a BMI of less than 25, according to Brian Wolpin, MD, MPH, of the Dana-Farber Cancer Institute in Boston, Mass., and colleagues.

Patients who had higher prediagnostic BMI were also more likely to present with more advanced-stage disease; 72.5% of obese patients had metastatic disease versus 59.4% of healthy-weight patients (P=0.02), they wrote online in the Journal of Clinical Oncology.

A number of consumables — from soft drinks to bacon and sausage to heavy alcohol consumption – have been associated with increased risk for pancreatic cancer, while foods with antioxidants, sun exposure, and other sources of vitamin D have been shown to offer a protective effect.

The authors also noted that obesity itself is a risk for pancreatic cancer, which may be the result of “alterations in systemic metabolism as a consequence of peripheral insulin resistance.” They used this association as a jumping-off point to evaluate the association of prediagnostic BMI with survival in 902 pancreatic cancer patients from two prospective cohorts, the Nurses’ Health Study and the Health Professionals Follow-Up Study.

Preclinical BMI was used to establish the association due to “weight loss that often accompanies subclinical or newly diagnosed pancreatic malignancy.”

Prediagnostic BMI was the participant’s BMI as reported at baseline measure in each study. Researchers also gathered data on age, race, smoking status, multivitamin use, weekly hours of physical activity, alcohol intake, energy intake, and history of diabetes.

Medical records indicated date and stage of cancer at diagnosis, and included local disease amenable to surgical resection, locally advanced disease that was not resectable without distant metastases, distant metastatic disease, or unknown stage.

Diagnoses were reported up to 2010 or through follow-up of a participant’s death.

Survival time was calculated as time from diagnosis to death or the May 2010 study conclusion.

Mean participant age at baseline was 57.8, median time between baseline BMI and pancreatic cancer diagnosis was 14.7 years, mean baseline BMI was 25.9, and 36% of participants were considered overweight, while 15% were obese.

By disease stage, 19.7% had localized disease, 15.3% had locally advanced disease, and 65% had metastatic disease.

Median survival by stage was 16 months with localized disease, 8 months with locally advanced disease, and 3 months with metastatic disease.

The association between BMI and reduced pancreatic cancer survival remained significant after adjustment for age, sex, cohort enrollment, race, smoking status, and time period of diagnosis (HR 1.53, 95% CI 1.11-2.09) comparing obese versus healthy-weight patients.

A secondary analysis also showed that cumulatively updated BMI was associated with survival, where a disease stage-adjusted model found the death hazard ratio was 1.37 (95% CI 1.00-1.88) comparing high versus healthy BMI.

Future studies could use the same data to analyze the effects of chronic exposure to obesity on patient survival, as well as other potential confounders in mortality in obese pancreatic cancer patients, such as complications in surgery or systemic therapies, the authors wrote.

They cautioned that the study was limited by prospective design, potential misclassification due to imperfect recall of BMI, and lack of generalizability of the study populations.