Oct. 12, 2011 -- A simple saliva test may one day help doctors diagnose people with pancreatic cancer before it has spread.
As of now, there is no early screening test for pancreatic cancer. There often are no symptoms until the cancer has begun to spread, which accounts for its poor survival rate.
New research in the journal Gut suggests that saliva -- and the bacteria it contains -- may hold the key to an earlier diagnosis of pancreatic cancer.
According to the study, there are differences in the types and prevalence of certain bacterial strains in the saliva of people with pancreatic cancer.
"We are seeing differences in the bacteria that are colonized in the mouth of patients with pancreatic cancer as opposed to other pancreatic diseases," says study researcher James J. Farrell, MD. He is the medical director of the Pancreas Center at the UCLA David Geffen School of Medicine. "This piece of data adds another brick in the wall of what is going on with oral health and pancreatic cancer."
But experts not connected with the study are quick to caution that such a test for pancreatic cancer is not ready for prime time.
The pancreas, a long, flat gland that lies in the abdomen behind the stomach, produces enzymes that help with digestion and certain hormones that maintain the proper level of blood sugar.
The American Cancer Society estimates that about 44,030 people will be diagnosed with pancreatic cancer in the U.S. in 2011, and 37,660 people will die from this disease in 2011.
Early Screening Test for Pancreatic Cancer
A test that could diagnose pancreatic cancer early or even in its precancerous stages is the Holy Grail, Farrell tells WebMD.
Researchers are now trying to validate some of these indicators identified in the study see if they could be used as an early detection tool for pancreatic cancer. In the future, "a saliva test which is less invasive than a blood test or endoscopy may be used as a broad screening test to pick out patients who would need further screening," he says.
The researchers first found differences in the bacteria in the spit of 10 people with pancreatic cancer, which had not yet spread, and 10 people without pancreatic cancer. Next, they analyzed saliva from 28 pancreatic cancer patients and 28 healthy people to verify their findings.
They also compared these findings with those from 27 people who had chronic inflammation of the pancreas, a condition that may increase risk for pancreatic cancer.
Two types of bacteria, Neisseria elongata and Streptococcus mitis, were less common in people with pancreatic cancer. Levels of another bacteria species, Granulicatella adjacens, were significantly higher among people with pancreatic cancer.
Whether these bacteria are causing pancreatic cancer or merely reflecting its presence it is not known, but researchers suspect it is the former.
"We don't have a handle on this yet, but we suspect that the inciting event is the colonization or alteration of bacteria in the mouth," Farrell says.
This isn't the first time that gum disease has been linked to health problems elsewhere in the body. Gum infection causes inflammation in the mouth, and body-wide inflammation is also linked to many diseases including heart disease, stroke, diabetes, and certain cancers.
Test Not Ready for Prime Time
Margaret Tempero, MD, says the new paper is interesting, exciting, and evocative, but a lot more work is needed. She is the director of research programs and deputy director at the UCSF Helen Diller Family Comprehensive Cancer Center in San Francisco.
"Everybody would agree that an early diagnostic test for pancreatic cancer would be the key ingredient to curing more patients," says Tempero, who is also a member of the Pancreatic Cancer Action Network's scientific advisory board. "We know that if we can diagnose pancreatic cancer early and if we have a chance to remove the cancer, we can cure it, so anything that gets us close to that is important."
But -- and it's a big but -- it's not likely there will ever be a simple indicator that says you've got pancreatic cancer.
"Taking a blood test or a swab of saliva and saying we have a test for pancreatic cancer isn't likely to happen," she says.
Such a test may one day be the first layer in a screening program.
"We may get a group of people in whom we can say, 'This pancreas is not right,' and therefore we should do more testing," Tempero says. In these cases, people could get follow-up with specialized imaging tests to look at the pancreas to see exactly what is going on.
"This study is provocative," agrees Peter Kozuch, MD. He's a pancreatic cancer expert at Beth Israel and St. Luke's-Roosevelt Hospitals, which are part of the Continuum Cancer Centers of New York.
"There is an unmet need for identifying pancreatic cancer or precancerous lesions in the pancreas as early as possible because this disease, once advanced, is highly [lethal]" says Kozuch. He is also an associate professor of clinical medicine at Albert Einstein College of Medicine in the Bronx, N.Y.
Still, this test is not ready for prime time yet, he says.
To really develop an early detection program for pancreatic, or any, cancer, "we need to identify an at-risk group, a method for finding the disease at an early point, and an intervention that improves survival," Kozuch tells WebMD.
The new study may help with the first step in this multistep process, he says.
Gagandeep Singh, MD, is less optimistic about the possibility of diagnosing pancreatic cancer based on bacteria in saliva. He is the chief of hepatobiliary and pancreatic surgery at the City of Hope, a cancer center located in Duarte, Calif.
It does, however, help advance the theory that chronic inflammation may increase the risk for pancreatic cancer, he tells WebMD.
"Chronic inflammation is definitely associated with chronic pancreatitis, which may be a risk for pancreatic cancer," Singh says. Gum disease can be a sign of inflammation in the mouth.
"We can't say that inflammation in your mouth is a representation of pancreatic cancer or chronic pancreatitis yet," he says.