Doctors might be able to pick up early signs of pancreatic cancer by looking inside the intestine, a new study suggests.

In the study, doctors used a probe to examine the small intestine, close to where it touches the pancreas, looking for abnormalities that signal cancer is nearby.

The experimental test detected pancreatic cancer in all 12 of the study participants with the condition, the researchers say, though it also gave a positive result in some cases where the cancer didn't exist.

The finding suggests such a test could one day be used to screen patients at high risk for pancreatic cancer, to detect the disease in its early stages, said study researcher Dr. Michael Wallace, chairman of the Division of Gastroenterology at the Mayo Clinic in Jacksonville, Fla.

Currently, pancreatic cancer is diagnosed with an imaging scan followed by an invasive biopsy. Because patients often have no symptoms while the disease is in its early stages, the condition is usually not diagnosed until it is advanced. As a result, pancreatic cancer is often incurable when detected — 94 percent of patients diagnosed with the disease die within five years.

However, the new study was small, just 21 people, and a larger study is needed to validate the results, the researchers said.

In recent years, researchers have been investigating minimally invasive ways to find cancer by looking for so-called "field effects," which are changes that occur in nearby tissues as a result of cancer growth. For instance, tumors require an increased blood supply. This means tissue in the vicinity of a cancer might have enlarged blood vessels, and a depletion of oxygen in the blood. Wallace likened the test to a metal detector that beeps faster the closer you get to the cancer.

The new study involved 12 patients who had been diagnosed with pancreatic cancer, and nine healthy people who did not have the disease.

The researchers examined participants' intestines with a probe called an endoscope, which is a flexible tube with a light. The instrument measured the size of nearby blood vessels, as well as the concentration of oxygen in the blood.

A different group of researchers analyzed the measurements, and did not know which participants had cancer.

While the test was 100 percent accurate in detecting the cancer where it existed, it was less accurate in excluding people who did not have the disease. One of the healthy people was given a positive result, and another was borderline-positive.

"Finding a minimally invasive screening test for such a lethal cancer has been a holy grail in cancer diagnostics for a long time," said Dr. David Robbins, associate chief of the Center for Advanced Therapeutic Endoscopy at Lenox Hill Hospital in New York, who was not involved in the study. The findings from this study are exciting, although they are preliminary and need to be backed up by further research, Robbins said.

The intestinal probe in this study represents an advance over the tests we have now for pancreatic cancer, which are used to diagnose the cancer and screen people at high risk for the disease, Robbins said. Currently, these tests, such a special type of ultrasound, require specialized training and equipment. And the tests, which also include magnetic resonance imaging (MRI), can miss up to 25 or 30 percent of cancers, Robbins said. The test described in this study, on the other hand, can be performed with routinely available equipment, and is highly accurate.

Further study is needed to see how well the test can detect small cancers, which are the most curable, Robbins said.

The researchers plan to conduct a larger clinical trial with 600 participants to validate their findings.

If the results are confirmed, the test could be given to people with a family history of pancreatic cancer, or those with chronic inflammation of the pancreas, a condition that increases the risk of the disease, Wallace said.

Although the test is minimally invasive, the cancer is still very rare, so it would not be appropriate to give to everyone, Wallace said.

The study will be presented today (May 21) at a meeting of gastrointestinal researchers in San Diego.

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