Blood Test Might Spot Pancreatic Cancer Early, Study Finds
But not early enough to make a big difference in survival rates, an expert says
Friday, March 29, 2013
"This new diagnostic test may be a safe and easy screening method that could improve the prognosis of patients with pancreatic cancer through earlier detection," said lead researcher Dr. Masaru Yoshida, an associate professor in the division of metabolomics research at Kobe University Graduate School of Medicine. "A drop of blood contains a lot of information."
Currently, the 5-year survival rate for pancreatic cancer is less than 5 percent, largely because the cancer usually has spread by the time it is detected.
The new approach relies on metabolomics technology, an emerging science that focuses on small molecules. The blood test measures byproducts of metabolism, called metabolites, found in the blood.
By looking for differences between the levels of metabolites in patients with and without pancreatic cancer, the researchers are able to identify those with cancer.
Finding pancreatic cancer earlier means more patients can have the tumor removed and live longer than most patients do now, Yoshida noted.
"Conventional tests using blood or imaging are not appropriate for pancreatic cancer screening and early detection, so new screening and diagnostic methods for pancreatic cancer are urgently required," Yoshida said.
Currently, in more than 80 percent of cases of pancreatic cancer, the cancer has metastasized, or spread, making it inoperable, he explained.
One expert doesn't think this test is a breakthrough.
"It's an improvement, but not a breakthrough," said Dr. James D'Olimpio, director of supportive oncology at North Shore-LIJ Cancer Institute in Lake Success, N.Y.
"The problem is it's not early enough," he said.
Even if the cancerous tumor can be removed, it's usually too late, he said. By the time the cancer is detected, even in the early stage suggested by their test, the cancer has most likely spread beyond the pancreas, D'Olimpio pointed out.
"The test is able to detect cancer when it is at stage 1, but it's a fatal disease once it gets past stage 0," D'Olimpio said. (Staging, which refers to the severity of a person's cancer, usually runs from 0 to 4.)
"The cure rates of these patients is still going to be less than 20 percent," he said.
For the study, published online March 29 in Cancer Epidemiology, Biomarkers & Prevention, the researchers used a technology called gas chromatography mass spectrometry to analyze the blood from study participants.
The researchers randomly assigned 43 pancreatic cancer patients and 42 healthy participants to what they called a training set, where they made their initial findings. To validate their findings, they also tried the test on 42 patients with pancreatic cancer, 41 healthy people and 23 people with chronic pancreatitis (inflammation of the pancreas).
The researchers found 18 metabolites that were significantly different in patients with pancreatic cancer, compared with the healthy patients.
They refined their test using four metabolites to identify patients with pancreatic cancer.
The test had a sensitivity of 71.4 percent and a specificity of 78.1 percent when it was used with patients with pancreatic cancer and patients with chronic pancreatitis, the researchers reported. Sensitivity measures the accuracy of the test in identifying people with pancreatic cancer and specificity measures the accuracy of the test in weeding out those who didn't have the disease. Chronic pancreatitis is sometimes mistaken for cancer, so cutting down false positives is important.
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