Researchers found that patients with pancreatic cancer had certain particles in their bloodstream not found in healthy patients. The presence of those particles could determine, with 100 percent accuracy, who had pancreatic cancer and who did not, the study found.

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Researchers at MD Anderson Cancer Center in Houston believe they have found a path to early detection that could yield more effective treatment of pancreatic cancer, an illness so lethal that just 7 percent of patients survive for five years after diagnosis.

In a study published in Wednesday’s issue of the journal Nature, the researchers found patients with pancreatic cancer had certain particles in their bloodstream not found in healthy patients or in those with other types of pancreatic disorders. The presence of those particles could determine, with 100 percent accuracy, who had pancreatic cancer and who did not, the study found.

While the test must undergo more rigorous study before it can be used routinely, it could provide a reliable, noninvasive way of finding the cancer before it’s too late to treat it.

‘’If it pans out, it’s a game-changer, and we’re aware that our patients really need that right now,’’ said Dr. Raghu Kalluri, chair of cancer biology at MD Anderson and a co-author of the study.

The National Cancer Institute estimates 48,960 pancreatic-cancer cases will be diagnosed this year, and it will kill 40,560 people.

Pancreatic cancer has among the worst outcomes of any cancer. The pancreas is deep within the body, so early tumors cannot be seen or felt, and 4 of 5 patients are diagnosed only after it has spread. Patients usually have no symptoms until the cancer has spread to other organs. While surgery to remove the tumor or the organ can cure up to 50 percent of early-stage pancreatic cancer, doctors see few patients in that stage.

‘’It’s almost invariably advanced,’’ said Dr. Kirk Heyne, a medical oncologist at the Houston Methodist cancer center who was not involved in the study. ‘’Probably 15 percent of people can be taken to surgery.’’

Even after diagnosis, there are no good ways of tracking what is happening with the cancer. Patients must undergo repeated biopsies or CT scans to determine whether the treatment is working or whether their cancer has progressed or recurred.

Researchers found the marker by looking at exosomes, tiny bundles containing DNA and other genetic material, released by the body’s internal cells.

They compared exosomes from healthy and cancerous cells and found the cancer exosomes contained a particular protein. By searching for exosomes with this protein in the bloodstream, the researchers could detect and quantify the amount of cancer in the body.

They then screened the blood of hundreds of pancreatic-cancer patients, diagnosed at different stages, and hundreds of healthy donors for exosomes containing the protein. In addition to MD Anderson, institutions in Germany and Spain participated in the study.

‘’When it was positive for it, it was always in the cancer patients,’’ Kalluri said, “never in the hundreds of healthy subjects or those who didn’t have pancreatic cancer. The fine difference with which it was able to distinguish is unheard of in the cancer field.’’

The test had zero false positive and zero false negative results.

Moreover, the study found the more advanced the patient’s cancer, the more exosomes in their blood, and when tumors were removed with surgery, levels of the exosomes dropped.

University of California, San Francisco, cancer physician Alan Venook cautioned, that much more needs to be known. “The issue is, can you detect these in patients that don’t have advanced cancer?” Venook said. “The answer is, we don’t know.”

The numbers tested by the MD Anderson researchers — 56 patients with pancreatic cancer, six with chronic pancreatitis and 20 healthy controls — aren’t nearly large enough to draw such conclusions. And getting a clear answer, Venook said, would probably require lengthy and expensive studies on very large populations.

“Don’t get me wrong, this is where we start. This is a very cool observation, well worth following. But this is not a biomarker yet.”

The test could be used primarily in patients at higher risk for pancreatic cancer, such as those who are obese, diabetics, smokers or those with a family history of the disease.