CHICAGO, July 23 (UPI) -- Gastric or pancreatic cancer patients live longer when they are treated at cancer centers or high-volume U.S. hospitals, researchers said.

Researchers at Northwestern University's Feinberg School of Medicine said lymph node metastases -- indicating the spread of cancer -- have been shown to predict patients' prognosis after cancer tissue is removed from the stomach or pancreas.

Dr. Karl Bilimoria, the study's lead author, said that if too few lymph nodes are examined for malignant cells, a patient's cancer may be incorrectly classified, which alters the prognosis, treatment decisions and eligibility for clinical trials.

Current guidelines recommend evaluating at least 15 regional lymph nodes for gastric and pancreatic cancer.

The study, published in the Archives of Surgery, found that patients at a high-volume hospital or a hospital designated as a National Cancer Institute comprehensive cancer center or as part of the National Comprehensive Cancer Network were more likely to have at least 15 lymph nodes evaluated than patients undergoing surgery at community or low-volume hospitals.