Obesity Before Pancreatic Cancer Shortens Survival

Nick Mulcahy

October 21, 2013

Patients with pancreatic cancer who were obese in the years before their diagnosis have reduced survival, according to research published online today in the Journal of Clinical Oncology.

The investigators found that patients with pancreatic cancer who had a prediagnostic body mass index (BMI) in the obese range lived 2 to 3 months less than patients who had a healthy weight before their diagnosis.

They used prospectively collected BMI data on 902 patients with pancreatic cancer from 2 large, long-term cohort studies of health professionals.

Findings from previous case–control studies have been similar, but they were retrospective. Results from this prospective study strengthen the evidence on the subject, according to one expert.

"While previous retrospective studies suggested a link between obesity and pancreatic cancer survival, the prospective nature of this study makes the findings more reliable," said Smitha S. Krishnamurthi, MD, from Case Western Reserve University in Cleveland, in a press statement. She was not involved with the study, but offered her comments as a member of the Cancer Communications Committee at the American Society of Clinical Oncology.

Clinicians can share the results with patients in general practice and oncology, suggested a study author.

"This study adds to mounting evidence for the role of weight control in improving outcomes for patients with cancer. It also reinforces the importance of maintaining a healthy weight throughout your life, which may lead to better outcomes after diagnosis and help prevent pancreatic cancer from developing," said senior study author Brian M. Wolpin, MD, MPH, from the Dana-Farber Cancer Institute and Harvard Medical School in Boston, in a press statement.

Obesity Independent of Other Factors

Dr. Wolpin and his colleagues found that the association between prediagnostic BMI and survival was independent of other known predictors of survival with this cancer.

On a multivariable analysis that compared especially obese patients (BMI ≥35 kg/m²) with healthy-weight patients (BMI <25 kg/m²), the adjusted hazard ratio (HR) for death was 1.53 (trend < .001). The analysis adjusted for differences in age, sex, race/ethnicity, smoking status, and disease stage.

The association between obesity and shortened survival was statistically strongest for people who were overweight 2 decades before their diagnosis. Specifically, in a subset of 202 patients for whom BMI collected 18 to 20 years before diagnosis was available, the HR for death was 2.31 (P trend = .001).

Dr. Wolpin and colleagues acknowledge that they used overall — not disease-specific — survival, which is a limitation of their study. However, pancreatic cancer is so lethal, overall survival is "a good surrogate," they say.

Median overall survival for all patients was 5 months. For patients with metastatic disease, median survival was 3 months; for patients with advanced disease, it was 8 months; and for patients with localized disease, it was 16 months.

Pancreatic cancer is the fourth leading cause of cancer-related death in the United States. Most patients with pancreatic adenocarcinoma, which accounts for more than 90% of new cases, survive less than a year after their diagnosis. Only 5% survive 5 years after diagnosis, the investigators report.

This study not only strengthens the literature on BMI and pancreatic cancer outcome, it adds to a relatively limited body of information about prognostic factors, they note.

For those with pancreatic cancer, "the length of patient survival is greatly influenced by disease stage at presentation, but few other markers of survival have been well characterized," they write.

Obese Patients Tend to Present With More Advanced Disease

The investigators evaluated the association between BMI in 1970s and 1980s and survival after a diagnosis of pancreatic cancer in participants from two cohorts: the Nurses' Health Study and the Health Professionals Follow-up Study.

Participants were surveyed on demographics, medical history, and health behaviors. Deaths were ascertained from next of kin, the postal service, and the National Death Index.

The investigators used World Health Organization (WHO) criteria to categorize body mass. A BMI from 18.5 to 24.9 kg/m² was considered healthy weight, from 25.0 to 29.9 kg/m² was considered overweight, and 30 kg/m² or higher was considered obese. For some analyses, the sample size was adequate to further classify the obese group into 2 categories: 30.0 to 34.9 kg/m² and 35 kg/m² or higher.

No statistically significant differences were seen in study cohort, smoking status, or disease stage. However, when baseline BMI groups were compared (≥35 vs <25 kg/m²), the association was stronger for never-smokers (HR, 1.61; trend = .002) than for ever-smokers (HR, 1.36; trend = .63).

Higher prediagnostic BMI was also associated with more advanced stage at diagnosis. More patients with a BMI of 30 kg/m² or higher presented with metastatic disease than with a BMI below 25 kg/m² (72.5% vs 59.4%; = .02).

This study was partly funded by the National Cancer Institute, the American Society of Clinical Oncology Conquer Cancer Foundation, the Howard Hughes Medical Institute, the Lustgarten Foundation, and Promises for Purple. The authors have disclosed no relevant financial relationships.

J Clin Oncol. Published online October 21, 2013. Abstract


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